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Professor Bijan Samali

Biography

Professor Samali is the holder of a Personal Chair in Structural Engineering at the University of Technology, Sydney. He has been with UTS for 23 years. His main areas of research includes Structural dynamics and its applications to wind and earthquake engineering (in particular structural vibration control caused by environmental loads) and more recently use of smart materials and dynamic assessment and health monitoring of bridges and buildings. He is the author of over 250 scholarly publications and speaker at many national and international conferences. He has also been involved with over 100 major projects as a specialist consultant over the years including major projects with Roads and Traffic authority of NSW and the Institution of Public Works Engineering, Australia with respect to testing of old bridges, particularly timber bridges. He is currently supervising 9 PhD and 2 ME students with another ten having graduated over the last 8 years.

Professional

Member of many National and International associations. Details are:

  • Charter Member- Structural Engineering Institute of the American Society of Civil Engineers
  • Member of American Society of Civil Engineers (ASCE).
  • Member of Engineers, Australia.
  • Member of the Council on Tall Buildings and Urban Habitat
  • Member of International Association for Bridge and Structural Engineering
  • Member of Australian Earthquake Engineering Society
  • Member of ASCE Committee on Structural Control (since October 2002)
Image of Bijan Samali
Casual Academic, University Casual Academics
Core Member, Centre for Built Infrastructure Research
BSc (GWU), MSc (GWU), DSc (GWU)
 

Research Interests

  • Analytical and experimental investigation of active and semi-active control devices to reduce dynamic response of structures subjected to severe wind and seismic loading using shake table and wind tunnel tests
  • Analytical and experimental investigation of liquid dampers to reduce dynamic response of structures subjected to severe wind and seismic loading using shake table and wind tunnel tests
  • Seismic performance of base isolated structures
  • Use of Shape Memory Alloys (SMA)and in active control of structures
  • Use of smart materials in structural control applications, particularly MR and fluids and elastomers
  • Study of seismic performance of low cost mud brick buildings in third world countries
  • New technologies for developing and sustaining physical infrastructure
  • Determining in-service conditions and load rating of timber, concrete and steel bridges using dynamic testing techniques
  • Design and analysis of earthquake resistant structures
  • Retrofitting of under-strength or damaged concrete structures by fiber reinforced composites
  • Experimental Modal Analysis of Framed Building Structures
  • Damage detection and structural health monitoring of structures
  • Seismic strengthening of Adobe mudbrick houses using local, low tech materials and techniques
  • Structural properties of high performance concrete elements using waste materials as cement substitute
Can supervise: Yes
Registered at Level 1 (full registration with no restriction)

  • Loading on Building Structures
  • Structural Dynamics and Earthquake Engineering
  • Wind Engineering

Chapters

Samali, B., Li, J., Dackermann, U. & Choi, F. 2011, 'Vibration-Based Damage Detection for Timber Structures in Australia' in Chan, T.H.T. & Thambiratnam, D.P. (eds), Structural Health Monitoring in Australia, Nova Science Publishers, New York, USA, pp. 81-108.
The use of non-destructive assessment techniques for evaluating structural conditions of aging infrastructure, such as timber bridges, utility poles and buildings, for the past 20 years has faced increasing challenges as a result of poor maintenance and inadequate funding. Replacement of structures, such as an old bridge, is neither viable nor sustainable in many circumstances. Hence, there is an urgent need to develop and utilize state-of-the-art techniques to assess and evaluate the "health state" of existing infrastructure and to be able to understand and quantify the effects of degradation with regard to public safety. This paper presents an overview of research work carried out by the authors in developing and implementing several vibration methods for evaluation of damage in timber bridges and utility poles. The technique of detecting damage involved the use of vibration methods, namely damage index method, which also incorporated artificial neural networks for timber bridges and time-hased non-destructive evaluation (NDE) methods for timber utility poles. The projects involved successful numerical modeling and good experimental validation for the proposed vibration methods to detect damage for simple beams subjected to single and multiple damage scenarios and was then extended to a scaled timber bridge constructed under laboratory conditions. The time-based NDE methods also showed promising trends for detecting the embedded depth and condition of timber utility poles in early stages of that research.
Aboura, K., Samali, B., Crews, K.I. & Li, J. 2009, 'The Use of Stochasatic Processes in Bridge Lifetime Assessment' in Agbinya, J.I., Biermann, E., Hamam, Y., Rocaries, F. & Lal, S.K. (eds), Biomedical and Environmental Sensing, River Publishers, Denmark, pp. 295-316.
We introduce an approach for modelling the structural deterioration of components of bridges for maintenance optimization purposes. The Markov chain model is found in the maintenance and repair problems since the early 60's, is introduced to the maintenance of road infrastructure in the 1980's, and is made to drive the current bridge maintenance optimization systems. While this model results into solvable programming problems and provides a solution, there are a number of criticisms associated with it. We highlight the shortfalls of the Markov model for bridge lifetime assessment and promote the use of stochastic processes.

Conferences

Fatahi, B., Sadeghi Hokmabadi, A. & Samali, B. 2014, 'Seismic Performance Based Design for Tall Buildings Considering Soil-Pile- Structure Interaction', GeoShanghai 2014 (Advances in Soil Dynamics and Foundation Engineering GSP 240), ASCE, USA, pp. 333-342.
Soil-Structure Interaction (SSI) plays a significant role in seismic response of the structures by altering the dynamic properties of the system and increasing the lateral deflection which in turn could change the performance level of structures. In this study, in order to experimentally investigate the influence of different types of foundations on SSI phenomena, a series of shaking table tests has been conducted considering four different cases, namely: (i) fixed-base structure representing the situation excluding the soil-structure interaction; (ii) structure supported by shallow foundation on soft soil; and (iii) structure supported by floating pile foundation in soft soil, and (iv) structure supported by end-bearing pile foundation in soft soil. Benchmark earthquakes including the 1995 Kobe, the 1994 Northridge, the 1968 Hachinohe, and the 1940 El Centro earthquakes are adopted. Results indicate that presence and type of pile foundations change the dynamic characteristics and behaviour of the superstructure which should be considered in predicting the damage level of structural and non-structural elements.
Abtahi, P., Samali, B., Zobec, M. & Ngo, T.D. 2013, 'Application of flexible facade systems in reducing the lateral displacement of concrete frames subjected to seismic loads', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 241-245.
Faade systems, as an integral part of multi-storey buildings, and as non-structural systems are susceptible to potential failurewhen subjected to severe environmental forces such as earthquakes, if not designed properly. In this paper an alternative method using movable faade systems as an energy absorbing device is proposed in order to decrease the amount of energy imparted to the main structure during seismic activities. Analytical investigation concerning inter-storey drift limits of main structures and seismic drift assessment methods of glazed faades will be conducted. SAP2000 program is used for the numerical analyses. A series of inelastic time history analyses are carried out to determine the behaviour and response of the proposed system in a typical concrete frame structure under two earthquake records. Application of flexible connections in faade systems can, if properly designed, reduce the inelastic deformation of the structural models in comparison to the case without flexible connections.
Ghosni, N., Samali, B. & Vessalas, K. 2013, 'Evaluation of mechanical properties of carpet fibre reinforced concrete', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 275-279.
Incorporating suitable material in concrete to improve its performance is an important consideration in the construction industry. Using short fibres as an additive to improve its mechanical properties has been of great attention. Different types of fibres can be used as intrinsic reinforcement to enhance concrete performance. Some of the fibres used in concrete are recycled waste materials such as carpet fibres. This paper aims to investigate the static properties of fibre reinforced concrete (FRC) utilising short carpet fibres shredded and prepared from the carpet industry waste. Thereafter, the economic considerations regarding use of carpet fibres in concrete are discussed. There have not been any comprehensive studies on the effectiveness of carpet fibres in concrete, whereas there is a more comprehensive literature available for other types of fibres such as steel fibres. The effect of adding recycled carpet fibres on the strength development of FRC have been studied and the results are compared to control concrete. Fresh properties i.e. slump, air content and wet density and hardened properties i.e. compressive strength and modulus of rupture after 7 and 28 days of ageing are reported.
Kabir, M.I., Shrestha, R. & Samali, B. 2013, 'Effects of temperature, relative humidity and outdoor environment on FRP-concrete bond', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 299-304.
This paper presents the results of an experimental study undertaken to investigate the effects of temperature, relative humidity and exposure to outdoor environment on externally bonded FRP-concrete connection performance.Two types of FRP, namely, carbon and glass, were externally bonded to concrete prisms of 300mm length, 200mm width and 150mm height with two part epoxy impregnation resin and the specimens were exposed to three different environmental conditions for extended durations. The bond strengths of control (unexposed) and exposed specimens were investigated by single-lap-joint shear test (pull-out test). Results of exposed specimens were compared to those of control specimens in terms of bond strengths, strain profiles and failure modes. Based on the results to date, the most significant degradation of bond strength was observed in specimens exposed to outdoor environment. Distinct change in behaviour of FRP-concrete bond has been observed from strain profiles plotted at different levels of applied loads after being exposed to three different environmental conditions.
Vessali, N., Valipour Goudarzi, H., Samali, B. & Foster, S.J. 2013, 'Investigating the arching action in reinforced concrete beams', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 369-374.
A 1D frame element model was used to study the development of arching action in a reinforced concrete member. The model is capable of capturing geometrical as well as material nonlinearity including concrete cracking and crushing and reinforcement yielding. To preserve the objectivity of results associated with softening of concrete, a non-local damage model is incorporated into the element formulation. The element formulation is outlined and the developed model was verified by xamples from the literature. Also, a parametric study is undertaken on a generic beam to demonstrate effects of different parameters, particularly the end rotational and translational stiffness and the concrete compressive strength on development of arching action. The results obtained from the analytical tool are compared with the results of a simple plastic hinge analysis and the enhancing effect of arching action is quantified accordingly.
Aoki, Y., Samali, B., Saleh, A. & Valipour Goudarzi, H. 2013, 'Assessment of key response quantities for design of a cable-stayed bridge subjected to sudden loss of cable(s)', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 387-392.
Stays of cable-stayed bridges have potential to lose their support instantly by extreme loadings such as earthquake, thunder strike, vehicle impact, wind and malicious attacks. The sudden loss of cable(s) provides unpredictable stress redistribution on the deck and towers, as well as the large deflections of the entire bridge. This phenomenon is the cause of one of the most critical situations for the cable-stayed bridges, termed zipper-type collapse? (i.e. the mechanism of the progressive collapse by the redistribution of stresses). Considering such a sudden loss of cable in the design of a cable-stayed bridge is essential. Although cable loss scenarios are associated with material as well as geometrical nonlinearities, in design of cable-stayed bridges, such an extreme loading scenario is analysed typically by using linear elastic models. In this paper, a linear elastic 2D and a fully nonlinear 3D finite element model of an idealised steel cable-stayed bridge are developed and analysed to determine the effect of sudden loss of cable on the progressive collapse of the bridge at global and local stress levels.A parametric dynamic analysis for the bridge model with different cable loss scenarios under symmetrical or unsymmetrical load cases is investigated. The bridge model studied in this paper showed that the 2D model can adequately capture global behaviour of the bridge. The 3D model showed the most significant stress concentration occurring under the symmetrical case are limited to small areas and are negligible.
Samali, B., Ngo, T.D. & Nguyen, C. 2013, 'Dynamic behaviour of flexible facade systems in tall buildings subjected to wind loads', From materials to structures: Advancement through innovation, CRC press/Balkema, balkema, Netherland, pp. 431-435.
In recent years many new devices, as energy absorber systems, have been introduced in tall building. But most of them have some disadvantages such as complexity of design and large spaces needed for their installation. Faade systems, as an integral part of high-rise buildings, and as non-structural systems are susceptible to potential failure when subjected to wind, if not designed properly. In this paper an alternative method using multi-skin faade systems as an energy absorbing device is proposed in order to decrease the amount of energy imparted to the main structure during high speed winds and cyclones. A series of elastic and inelastic time history analyses using SAP2000 have been carried out to assess the structural dynamic response of a proposed 45 storey building with reinforced concrete frame structure under a simulated harmonic wind load, which derived from three second gusts according to provisions of Australian wind code (AS/NZ 1170.2). The preliminary results indicate that it is possible to make use of the double skin faade system in tall buildings to work as a damper device, if the connections are properly designed, to minimise the wind induced vibrations of the primary structure as well as reducing inter storey drift.
Pun, R., Samali, B. & Valipour Goudarzi, H. 2013, 'Seismic performance improvement of stone masonry buildings in mud mortar', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 479-484.
In this paper, a new reinforcement method suitable for stone masonry houses built with mud mortar is presented. The effectiveness of such reinforcement system has been observed by bending strength test of rubble wall specimens prepared in the laboratory. Flexural strength test results with this intervention have shown that the wall can have large deformation without significant loss of strength. Such property is highly desired in buildings for resisting seismic loads. With due consideration to applicability and affordability of potential users, this technique seems as one of the best options for improving the seismic performance of the type of buildings under consideration.
Tabatabaiefar, S., Fatahi, B. & Samali, B. 2013, 'Inelastic lateral seismic response of building frames under influence of bedrock depth variations incorporating soil-structure interaction', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 587-592.
In this study, a fifteen storey moment resisting building frame is selected in conjunction with a soft clayey soil, representing soil class Ee, according to Australian Standards. Different bedrock depths including 10 m, 20 m, and 30m are employed in the numerical modelling using finite difference software FLAC 2D. The above mentioned frame has been analysed under two different boundary conditions: (i) fixed-base (no soilstructure interaction), and (ii) flexible-base (considering soil-structure interaction). Inelastic dynamic analyses under influence of different earthquake records for three mentioned bedrock depths are conducted, and the results in terms of inelastic lateral deflections and inter-storey drifts for the above mentioned boundary conditions are compared and discussed. The results indicate that the bedrock depth variations play a significant role in inelastic lateral seismic response of the building frame under the influence of soil-structure interaction. As the bedrock depth increases, lateral deflections and inter-storey drifts of the structures increase. The mentioned effects can change the performance level of the structures from life safe to near collapse or total collapse.
Li, Y.C., Li, J.C. & Samali, B. 2013, 'A novel adaptive base isolator utilising magnetorheological elastomer', From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012, pp. 763-767.
Base isolation is the most popular seismic protection technique for civil structures. However, research has revealed that the traditional base isolation system is vulnerable to two kinds of earthquakes, i.e. the near-fault and far-fault earthquakes, due to its passive nature.A great deal of effort has been dedicated to improve the performance of traditional base isolation systems for these two types of earthquakes. Controllable supplementary and energy-dissipation members, such as magnetorheological damper, friction damper or hydraulic fluid damper, have been proposed to reduce seismic responses of the building structures. However, with the introduction of additional control devices, the system complexity increases resulting difficulty in the system implementation and control system design. It would be ideal if a certain level of adaptability could be introduced into base isolation systems while maintaining the traditional outfit. This paper addresses the challenge facing the current base isolation practices and proposes a novel adaptive base isolator as a solution to the problem.A smart rubber, namely, magnetorheological elastomer (MRE), is utilised in this research for its magnetic field-sensitive material property as the main element in the novel device. The tradition base isolator design for a large-scale structure with laminated steel and MRE layers is adopted. To verify and characterise the performance of the MRE base isolator, experimental testing was conducted on UTS shake table facility. Experimental results show that after being energised with magnetic field, the maximum force and the stiffness of the novel device can increase by up to approximately 45% and 37%, respectively.With the field-dependent stiffness and damping, the proposed adaptive base isolator is very promising in meeting the challenges associated with the base isolation systems encountered in practice. 2013 Taylor & Francis Group.
Firouzianhaji, A., Saleh, A. & Samali, B. 2013, 'Finite element modeling of a beam-column connection in industrial storage racking structures', From materials to structures: Advancement through innovation - 22nd Australian Conference On The Mechanics Of Structures And Materials, CRC press/Balkema, Netherlands, pp. 813-818.
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Industrial storage racking structures are typically constructed using cold-formed steel sections and contain moment resisting frames in which the columns have slots punched in at regular intervals to enable the beams to be clipped into position at any desired high. Hence unlike in conventional steel construction the beam to column connections are typically not bolted or welded but rely primarily on hooks and bearing contact between components to achieve the connection. As a consequence, such connections are semi-rigid and when loaded to failure they exhibit non-linear stiffness characteristics that are attributed to both geometric and material non-linearity. Due to the slenderness and flexibility of industrial racks, it is important therefore to consider the effect of connection flexibility when preparing structural models of such racking systems. A research project is currently underway at University of Technology, Sydney to investigate the behaviour of such connections and its effect on the dynamic response of industrial storage racking systems. An important part of this research, which is the focus of this paper, is devising suitable finite element models of the connections and verifying their accuracy against experimental moment-rotation curves. By considering the real conditions that govern the connection response, the FE models include different features such as 3D geometric details, non-linear material behavior, large displacements and the phenomena of contact non-linearity. This paper presents finite element models of a typical beam-column connection used in industrial storage racking structures and compares their accuracy against experimental results. The computational effort required in the analysis of different modeling options will also be compared and the adequacy in incorporating the model in a dynamic/Seismic finite element analysis will be discussed.
Makki-Alamdari, M., Li, J. & Samali, B. 2013, 'A comparative study on the performance of the damage detection methods in the frequency domain', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 867-872.
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During last two decades, a vast number of damage detection methods have been proposed either in frequency or time domain. These methods normally have their own advantages and limitations or suitable applications; the purpose of this study is to examine the performance of the some popular methods on localisation a possible damage on a sample structure. All of the chosen methods are based on the frequency domain data and work based on proposing a damage sensitive indicator which contains spatial information. Mode shape curvature, frequency response functions curvature, modal strain energy, flexibility matrix and spatial wavelet transform were amongst those damage detection methods were chosen for this study. The case study considers a clamped-clamped beam which was modelled by solid elements in order to define several damage stages based on different crack depth. Damage was simulated by reduction in elastic modulus of the elements in damage zone. The transient response of the structure due to an external impact excitation was obtained by ANSYS and then polluted by different percentages of white noise. The time-domain responses at selected evenly-spaced locationswas then processed byMATLAB to achieve the FRFs and mode shapes respectively by applying Fourier transform and eigenvalue realization algorithm (ERA). Based on the obtained results, it was found that despite some of these methods were suggested by so many researchers, they completely fail in localising damage in the structure even at high level of damage severity.
Makki-Alamdari, M., Li, J. & Samali, B. 2013, 'A FRF-based damage detection method utilising wavelet decomposition', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 873-877.
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Damage in a structure causes deviation in dynamic responses of the structure either in frequency or time domain in comparison with its healthy status. The purpose of this study is to present a new damage detection method in order to detect and localize the structural damage. This novel algorithm is based on the directly-measured frequency response functions (FRFs). The approach is composed of three major steps: first, developing the curvature of FRFs which produces spatially distributed shape functions at each frequency coordinate, secondly, normalization of FRFs curvature in order to enhance the influence of the lower-frequency-band data; finally decomposition of the obtained profiles (normalized version of FRFs curvature) by conducting wavelet analysis to detect any possible structural abnormality through structure. The combination of these three steps leads to a robust algorithm in detection and localisation of any damage in the structure even at small levels which other FRF-based methods were unable to detect. There are some benefits with the presented method: first, this method does not need higher-frequency-range data which is hard to obtain in most civil applications; second, there is no need for baseline data from the intact structure; This is particularly attractive for practical applications as it opens an opportunity for online monitoring of the structural integrity without demanding for any previous data records of the structure. The performance of the method is evaluated on a numerical model and the effect of different parameters such as the location of the excitation point, the level and the location of the damage was studied; the results demonstrated that the method can efficiently identify the location of the damage in the structure even for damage at small levels.
Askari, M., Li, J. & Samali, B. 2013, 'Adaptive multiple forgetting factor recursive least square (AMFF-RLS) for real-time structural identification', From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012, pp. 879-884.
System identification refers to any systematic way of deriving or improving models of systems through the use of experimental and field testing input-output data. In the field of civil engineering, identification of the state of the structure during the dynamic loads, such as earthquake, to predict the current state of the structure and detect any damage or hazard,when it occurs, has posed a great challenge to the research community. Therefore, online and real-time structural parameters identification has recently drawn more attractions, although few research works have been reported especially for cases where measurement data are contaminated by highlevel noise. The Recursive Least Square with single forgetting factor has been widely used in estimation and tracking of time-varying parameters in the fields of electrical and mechanical engineering. However, when there are multiple parameters that each (or some) varies with a different rate, this method cannot perform well. On the other hand, a priori information on the changing rate of the parameters might not be available, and the forgetting factors must be updated adaptively. This paper presents a new adaptive tracking technique, based on the Recursive Least Square (RLS) approach with Adaptive Multiple Forgetting Factors (AMFF). The proposed method considers an adaptive rule for each of the forgetting factors assigned to each of the parameters and thus, enables simultaneous estimation of the time-varying stiffness and damping of the storeys of the structure. Numerical examples show that results of this RLS-based approach are accurate and robust, even when the observed data are contaminated with different types and significantlevels of noise. 2013 Taylor & Francis Group.
Dackermann, U., Li, J. & Samali, B. 2013, 'Transmissibility function analysis for boundary damage identification of a two-storey framed structure using artificial neural networks', From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012, pp. 891-896.
This paper presents a damage identification technique that uses output-only scalar transmissibility measurements of a structure to identify boundary conditions. A damage index is formulated based on output-only acceleration response measurements from ambient floor vibration. The damage index is analysed by a system of artificial neural networks (ANNs) to predict boundary condition changes of the structure. Using the data compression and noise filtering capabilities of principal component analysis (PCA), the size of the damage index is reduced in order to obtain suitable patterns for ANN training. To test the proposed method, it is applied to different models of a numerical two-storey framed structure with varying boundary conditions. Boundary damage is simulated by changing the condition of individual joint elements of the structure from fixed to pinned. The results of the investigation show that the proposed method is effective in identifying boundary damage in structures based on output-only response measurements. 2013 Taylor & Francis Group.
Adam, G., Samali, B., Battista, P. & McKinnon, M. 2013, 'A novel acid resistant green mortar for high corrosive environments', From Materials to Structures: Advancement through Innovation - PROCEEDINGS OF THE 22ND AUSTRALASIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, CRC PRESS / BALKEMA, UK, pp. 1005-1008.
A new type of repair mortar (Aegis G) based on sustainable technology and industrial cementitious by-products with less than 10% OPC is developed. The new product consists of specified additives, accelerators and reinforcing agents, specially developed for this technology. The new acid resistant mortar showed high rate of hardening under normal conditions: >20MPa in 7 days, >40MPa in 28 days and >47MPa in 56 days for all batches tested during the last two years. Besides high tensile and flexural strength and modulus of rupture, the new product has excellent long term resistance to corrosive environments with very low permeability and minimal changes in the mechanical properties. The tested samples prepared from the product did not show any changes in their dimensions while 60MPa OPC cubes eroded and/or vanished completely when immersed in 520% sulphuric acid for 512 weeks .The new product has low shrinkage with outstanding adhesion properties to most construction surfaces. The failure occurred within the substrate concrete and not at the interface. The Aegis G is designed to provide long term resistance to most corrosive environments. The product is a versatile material that can be hand/trowel applied as well as spray applied and can be used for long term protection in a number of different aggressive environments which include: (1) re-lining of sewer trunk lines and manholes, (2) use as acid resistant grout for back fill of lining systems, (3) as acid resistant grout for use with impressed current cathodic protection, (4) lining channels of drinking water which require ion leaching resistant cement.
Rijal, R., Samali, B., Shrestha, R., Gerber, C. & Crews, K.I. 2013, 'Dynamic performance of timber flooring systems', From Materials to Structures: Advancement through Innovation - Proceedings Of The 22nd Australasian Conference on the Mechanics of Structures and Materials, CRC press/Balkema, UK, pp. 1065-1070.
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This paper presents the modal parameters of a LVL timber flooring system with overall dimensions of 8.41.8m acquired from its finite element (FE) model. The FE model of the floor was created by joining three identical models of a timber floor module (beam) side by side rigidly. The overall length of each floor module was 8.4m and width of top flange was 0.6 m. The individual modules were tested under application of impact load using modal hammer under identical pin-roller boundary conditions. The calibrated FE model of the module was extended to model the flooring system. The behaviour of the floor is assessed based on the modal parameters. Results from the FE model will be correlated with results from experimental tests to be conducted in near future on the floor with the given dimensions at University of Technology Sydney.
Subhani, M., Li, J. & Samali, B. 2013, 'Behaviour of stress wave propagation in utility timber pole', From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012, pp. 1077-1082.
Non-destructive testing has been used for many years to evaluate the in situ condition of timber piles. Longitudinal impact is usually applied on the top of piles to induce longitudinal wave to detect faults in piles due to the fact that the longitudinalwave has less dispersive nature at lowfrequency. On the other hand,when it comes to evaluation of poles in situ, it is different as poles are partly embedded in soil and it is more practical to produce bending waves, as the top of the pole is not easily accessible. However, bending wave is known for its highly dispersive nature; especially in the low frequency range which is usually induced in low strain integrity testing. As bending wave can be considered as a hybrid of longitudinal and shear waves, it will be helpful, if it could detect the component of these twowaves separately.To do so, components of displacements or accelerations along radial and longitudinal directions need to be determined. By applying Fast Fourier Transform (FFT) on the signals, the dominant frequencies can be obtained. It has been found that, the longitudinal component decreases along radial direction which indicates the presence of bending wave component and this finding allows to the application of ContinuousWavelet Transform (CWT) on the longitudinal component of wave signals in order to obtain phase velocity. Phase velocities at different frequencies are then determined to draw the dispersive curve and compare with analytical phase velocity curve. The dispersion curve matched well with the analytical curve. 2013 Taylor & Francis Group.
Zabihi, Z., Shrestha, R., Samali, B. & Crews, K.I. 2013, 'Ultimate performance of timber connection with normal screws', From Materials to Structures: Advancement through Innovation - PROCEEDINGS OF THE 22ND AUSTRALASIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, CRC PRESS / BALKEMA, UK, pp. 1083-1088.
This paper presents the results of experimental push-out tests on two different types of timber composite connections using only normal screws as the shear connecter. The push out tests were conducted based on Eurocode 5 recommendations and the load-slip responses obtained from lab tests are used to determine the stiffness of the connections at serviceability, ultimate and near collapse levels, and the performance of the connections are assessed at ultimate load. Moreover, an analytical model is derived for each type of connection based on the experimental results and using a non linear regression, which can be implemented into non-linear FE analysis of timber beams with normal screws.
Nabavi, S., Nejadi, S. & Samali, B. 2013, 'Investigation on the mathematical models of chloride diffusion coefficient in concrete exposed to marine environment', From Materials to Structures: Advancement through Innovation - PROCEEDINGS OF THE 22ND AUSTRALASIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, CRC PRESS / BALKEMA, UK, pp. 1153-1158.
Degradation of reinforced concrete (RC) in maritime structures has become aworldwide problem due to its excessive costs of maintenance, repair, and replacement in addition to its environmental impacts and safety issues. Degradation of both concrete and steel which is the main reason of reduction in the service life of RC structures strongly depends on the diffusion process of moisture and aggressive species. In this paper, the major and popular mathematical models of diffusion process in concrete are surveyed and investigated. Predominantly in these models, the coefficient of chloride diffusion into the concrete is assumed to be constant. Whereas, experimental records indicate that diffusion coefficient is a function of time. Subsequently, data analysis and comparisons between the existing analytical models for predicting the diffusion coefficient with the existing experimental database are carried out in this study. Clearly, these comparisons reveal that there are gaps between the existing mathematical models and previously recorded experimental results. Perhaps, these gaps may be interpreted as influence of the other affecting parameters on the diffusion coefficient such as temperature, aggregate size and relative humidity in addition to the water cement ratio. Accordingly, the existing mathematical models are not adequate enough to predict the diffusion coefficient precisely and further studies need to be performed. At the present, an extensive experimental and analytical research in this regard is being conducted in the CBIR group, University of Technology Sydney.
Noushini, A., Vessalas, K., Ghosni, N. & Samali, B. 2013, 'Effect of polyvinyl alcohol fibre and fly ash on flexural tensile properties of concrete', From Materials to Structures: Advancement through Innovation - PROCEEDINGS OF THE 22ND AUSTRALASIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, CRC Press, UK, pp. 1165-1170.
This paper investigates the effect of synthetic fibre and fly ash (FA) on post peak response and fracture properties of concrete. Polyvinyl alcohol (PVA) fibres were added as intrinsic reinforcement to concrete and30%of cementwas replaced with fly ash as an environmental friendly additive to reduce cement consumption. Samples were prepared abiding by relevant standards and tested accordingly. Limit of Proportionality (LOP) of the mentioned concretes has been assessed. Notched rectangular prisms have been tested to evaluate the residual flexural tensile strength and limit of proportionality of conventional and FA modified concrete as well as fibre reinforced concrete (FRC). Cylindrical samples have been tested to determine the compressive strength and indirect tensile strength of each concrete. Tests have been conducted at 28 days of ageing. Results gathered from different mix designs are compared to control and other mixes.
Ghosni, N., Samali, B. & Vessalas, K. 2013, 'Energy Absorption and Flexural Toughness Evaluation of Fibre Reinforced Polymer Modified Concrete', Proceedings of the 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-8), International Center for Numerical Methods in Engineering (CIMNE), Spain, pp. 1122-1130.
This paper presents the effect of fibres on the behaviour of fibre reinforced concert (FRC) which nowadays is recognised for its energy absorption capacity as well as other benefits. Incorporating fibres in concrete, results in an ameliorated mix design which can dissipate energy and improve the fracture performance of concrete matrix. There are different types of test methods developed to measure the concrete energy absorption capacity, one of which is the four point bending test. This research work is on the flexural behaviour characterisation of polymer modified synthetic fibre reinforced concrete incorporating polypropylene (PP) fibres and styrene butadiene (SB) latex copolymer. Results of this study show that by adding PP fibres to concrete, toughness and energy absorption characteristics can be enhanced. By increasing the amount of fibre used in the concrete matrix this value can be increased. It has also been concluded that by adding fibres to the concrete matrix, the energy absorption characteristics can consequently be improved.
Nabavi, S., Nejadi, S. & Samali, B. 2013, 'Investigation on the durability of fibre reinforced concrete (FRC) exposed to marine environment', Proceedings of the 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures, International Center for Numerical Methods in Engineering (CIMNE), Barcelona, Spain, pp. 1934-1940.
This experimental investigation presents an improvement on the mechanical properties and durability of conventional concrete (CC) exposed to marine environment using synthetic fibre-concrete composites incorporating Polypropylene fibres. Conventional con
Sorourian, S., Keshavarzy, A., Ball, J.E. & Samali, B. 2013, 'Study of Blockage Effect on Scouring Pattern Downstream of a Box Culvert under Unsteady Flow', Proceeding of the 35th IAHR World Congress, Tsinghua University Press, Beijing, pp. 1-9.
Sharifi, N., Vessalas, K. & Samali, B. 2013, 'Assessment of compressive strength of elastomeric modified concrete incorporating waste tyre rubber', From Materials to Structures: Advancement through Innovation - PROCEEDINGS OF THE 22ND AUSTRALASIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, CRC PRESS / BALKEMA, UK, pp. 1187-1191.
This paper reports on the fundamental findings of utilizing Styrene Butadiene Rubber (SBR) waste tyre granules as a potential source for replacing coarse aggregate in elastomeric modified concrete (EMC). EMCs incorporating 2%, 4%, 6% and 10% of SBR granules (12-15 mm) are assessed for their fresh and hardened properties compared to control concrete devoid of SBR granule additions. Fresh concrete was investigated for slump, air content, and wet density while hardened concrete was evaluated for compressive strength at 7, 28 and 56 days of age. A decrease in slump, density up to 4% and compressive strength of 10 to 44% for 28 days of age, with the addition of SBR granules and an increase in the value of air content were observed.
Noushini, A., Samali, B. & Vessalas, K. 2013, 'Flexural Toughness and Ductility Characteristics of Polyvinyl-Alcohol Fibre Reinforced Concrete (PVA-FRC)', Proceedings of the 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-8), International Center for Numerical Methods in Engineering (CIMNE), Spain, pp. 1110-1121.
This paper presents the results of an experimental study investigating the effect of uncoated polyvinyl alcohol (PVA) fibres on the properties of hardened concrete. PVA fibre of varying lengths, 6 and 12 mm and aspect ratio (l/d) of 430 and 860, respectively, was utilised in different volume fractions of 0.125%, 0.25%, and 0.5%. In addition, 30% fly ash was also used as partial replacement of Portland cement in all fibre reinforced concrete (FRC) mixes. Uniaxial compression, splitting tensile, modulus of rupture (MOR) and modulus of elasticity (MOE) tests were performed following the Australian Standards to evaluate the mechanical poperties of PVA-FRCs. Fracture test is also conducted in accordance with European Standard in order to evaluate the residual flexural tensile strength and limit of proportionality of PVA-FRCs. Furthermore, the structural properties of reinforced concrete (RC) beams incorporating PVA fibres are investigated for their load-deflection behaviour using 4-point loading. Flexural toughness of the test specimens and peak load deflection were measured and discussed indicating to what extent the un-coated PVA fibre can enhance the brittle-like behaviour of concrete. Results show that adding PVA fibres to the mix generally improves the mechanical properties of concrete. Regarding the strength, the optimum fibre content goes to 0.25% for both fibre lengths and in the case of toughness and ultimate deflection 0.5% shows the highest values. An increase of 30% in ductility is noted for the RC beam incorporating 0.5% by volume fraction of 12 mm PVA fibre.
Nabavi, S., Nejadi, S. & Samali, B. 2013, 'Experimental investigation on mix design and mechanical properties of polymer (latex) modified concrete', Advanced Materials Research - vol 687 - Proceedings of the International Congress on Polymers in Concrete, TransTech, USA, pp. 112-117.
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This paper presents the experimental investigation to enhance the mechanical properties of Polymer Modified Concrete (PMC) incorporating Styrene Butadiene Rubber (SBR) and describes the potential of using PMC as a structural material. PMC has been used f
Sorourian, S., Keshavarzy, A., Samali, B. & Ball, J.E. 2013, 'Study of Blockage Effect on Scouring Pattern Downstream of a Box Culvert', From materials to structures: Advancement through innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, CRC Press/Balkema, London, pp. 741-744.
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ABSTRACT: This experimental study is concerning with the scouring at the outlet of a box culverts. The blockage of culverts has considered as an important factor on the scouring pattern at the outlet of the box culverts. To investigate the effect of blockage on scouring pattern at the downstream of box culvert, some experimental tests were carried out in a laboratory flume located in the Hydraulic Laboratory of University of Technology Sydney (UTS). The experimental tests were carried on in both blocked and non-blocked conditions and consequentially the effect of blockage on depth of scour hole is investigated. It was found that for flow with Froude number of 0.09 there is a 15% increase in the depth of scour hole for a box culvert with 40 percent blockage. Furthermore, the scour depth in blocked condition with the Froude number of 0.12 was 22% deeper than box culvert with non-blocked condition.
Yan, N., Li, J., Dackermann, U. & Samali, B. 2013, 'Numerical and experimental investigations of stress wave propagation in utility poles under soil influence', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 593-598.
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Over the past decades, different types of non-destructive testing (NDT) methods have been developed for the condition assessment of timber structures. Stress wave methods, which are based on stress wave propagation theory, are considered to be simple and cost-effective tools for identifying damage as well as embedment length of timber poles/piles. However, due to the lack of understanding on wave propagation in such structures, especially under the influence of surroundings such as soil, these methods encounter difficulties in producing reliable results. In this paper, an investigation was carried out on the wave propagation behaviour in utility timber poles under consideration of soil effects. The commercial finite element (FE) analysis software ANSYS was used to simulate stress wave propagation in a timber utility pole under the influence of soil. In order to verify the numerical findings, laboratory testing was also conducted in dual course with the numerical modelling.
Movassaghigilani, S., Ha, Q.P. & Samali, B. 2013, 'A Self-structuring Adaptive Fuzzy Control Scheme for Non-affine Nonlinear Systems used in Smart Structures', Proceedings of the 6th International Conference on Structural Health Monitoring of Intelligent Infrastructure, SHMII-6, The Hong Kong Polytechnic University, Hong Kong, pp. 415-415.
This paper presents an adaptive fuzzy control scheme for non-affine nonlinear multi-input multi-output smart structure systems. From an initial fuzzy system with a small number of rules, the self-structuring algorithm can add on membership functions and rules when needed. To limit the size of the system, the self-structuring algorithm replaces old membership functions with new ones and the number of rules is kept within a predefined upper bound. The proposed control scheme is applied to buildings that are subject to external excitations- in this case an earthquake. This structure is equipped with vibration suppression devices using current-controlled magneto-rheological dampers to surmount the energy of external excitations, which turns itself into a smart structure. Here, the encountered non-affine nonlinear dynamics is dealt with the proposed self-structuring adaptive fuzzy controller.
Sadeghi Hokmabadi, A., Fatahi, B. & Samali, B. 2013, 'Seismic Response of Superstructure on Soft Soil Considering Soil-Pile-Structure Interaction', Challenges and innovations in geotechnics. Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering, Presses des Ponts, Paris, France, pp. 547-550.
This paper presents results of shaking table tests and three dimensional numerical simulations to investigate the influence of Soil-Pile-Structure Interaction (SPSI) on the seismic response of mid-rise moment resiting buildings supported by end-bearing pile foundations. Three different cases have been considered, namely: (i) fixed-base structure representing the situation excluding the soil-structure interaction; (ii) structure supported by shallow foundation on soft soil; 8nd (iii) structure supported by end-bearing pile foundation in soft soil. Comparison of the numerical predictions and the experimental data shows a good agreement confirming the reliability of the numerical model. Both experimental and numerical results indicate that soil-structure interaction induces significant increase in the lateral deflections and inter-storey drifts of the structures on both shallow and end-bearing pile foundations in comparison to the fixed base structures. This increase in the lateral deformations and in turn inter-storey drifts can change the performance level of the structure during earthquakes which may be safety threatening.
Li, J., Li, Y., Li, W. & Samali, B. 2013, 'Development of adaptive seismic isolators for ultimate seismic protection of civil structures', Proceedings of SPIE - The International Society for Optical Engineering.
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Base isolation is the most popular seismic protection technique for civil engineering structures. However, research has revealed that the traditional base isolation system due to its passive nature is vulnerable to two kinds of earthquakes, i.e. the near-fault and far-fault earthquakes. A great deal of effort has been dedicated to improve the performance of the traditional base isolation system for these two types of earthquakes. This paper presents a recent research breakthrough on the development of a novel adaptive seismic isolation system as the quest for ultimate protection for civil structures, utilizing the field-dependent property of the magnetorheological elastomer (MRE). A novel adaptive seismic isolator was developed as the key element to form smart seismic isolation system. The novel isolator contains unique laminated structure of steel and MR elastomer layers, which enable its large-scale civil engineering applications, and a solenoid to provide sufficient and uniform magnetic field for energizing the field-dependent property of MR elastomers. With the controllable shear modulus/damping of the MR elastomer, the developed adaptive seismic isolator possesses a controllable lateral stiffness while maintaining adequate vertical loading capacity. In this paper, a comprehensive review on the development of the adaptive seismic isolator is present including designs, analysis and testing of two prototypical adaptive seismic isolators utilizing two different MRE materials. Experimental results show that the first prototypical MRE seismic isolator can provide stiffness increase up to 37.49%, while the second prototypical MRE seismic isolator provides amazing increase of lateral stiffness up to 1630%. Such range of increase of the controllable stiffness of the seismic isolator makes it highly practical for developing new adaptive base isolation system utilizing either semi-active or smart passive controls. 2013 SPIE.
Nabavi, S., Nejadi, S. & Samali, B. 2013, 'Lattice Based Simulation of Chloride Ingress in Uncracked and Cracked Concrete: Model Validation', Proceedings of the 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-8), International Center for Numerical Methods in Engineering (CIMNE), Spain, pp. 1934-1940.
This experimental investigation presents an improvement on the mechanical properties and durability of conventional concrete (CC) exposed to marine environment using synthetic fibreconcrete composites incorporating Polypropylene fibres. Conventional concrete (CC) as a reference specimen; and polypropylene fibre reinforced concrete (FRC) specimens with various proportions of polypropylene (PP) fibres were cast and exposed to simulated marine environment in the laboratory for 24 months. An accelerated corrosion experimental program carried out to measure the time to concrete cover cracking and anodic current. According to the results, a considerable enhancement on concrete durability in terms of increasing the time to crack initiation and reducing the anodic current for FRC was observed.
Nabavi, S., Nejadi, S. & Samali, B. 2013, 'Performance of Polymer-Concrete Composites Exposed to Harsh Environment', 3rd International Conference on Sustainable Construction Materials & Technologies, CRC Press, UK.
This paper presents an extensive experimental investigation on the durability of the polymer-concrete composites exposed to severe environment. In the last three decades, the premature deterioration of various reinforced concrete structures has been a widely recognized problem in the world due to its excessive costs of maintenance and repair, and also environmental impacts. Based on the literature review, diffusion of chloride into the concrete structures was found to be the major cause of the corrosion of steel reinforcement to promote their deterioration. Reinforced beam specimens were exposed to simulated marine environment for 24 months. Then, by utilizing accelerated chloride-induced corrosion test, the time to crack initiation was collected. The results revealed that the polymeric fibre-concrete composites not only increase the durability of the concrete, but also improve the mechanical properties of the concrete.
Nabavi, S., Nejadi, S. & Samali, B. 2013, 'PERFORMANCE OF POLYMER-CONCRETE COMPOSITES EXPOSED TO SEVERE ENVIRONMENT', 13th East Asia-Pacific Conference on Structural Engineering and Construction, The Thirteenth East Asia-Pacific Conference on Structural Engineering and Construction, Sapporo, Japan.
This paper presents a comprehensive experimental and theoretical investigation on the performance of polymer modified concrete (PMC) and fibre reinforced concrete (FRC) exposed to aggressive environmental conditions. Chloride-induced corrosion of steel in concrete is the main cause of premature deterioration of off-shore or on-shore reinforced concrete (RC) structures exposed to marine environment. For service life evaluation and prediction, the time of crack initiation in concrete cover can be considered as the most important criteria. Thus, the corrosion-induced crack initiation time and maximum anodic current intensity generated by corrosion process of embedded steel reinforcement in concrete were investigated in this paper. The specimens made of different categories of the concrete subjected to high concentrated Sodium Chloride solution and continuous cycles of wetting and drying for 24 months. Later, the accelerated electrochemical test was conducted to measure the time to concrete cover cracking and also anodic current intensity. Results proved that due to remarkable increase in time to cracking, the polymer-concrete composites increased the durability and service life of RC structures significantly.
Nabavi, S., Nejadi, S. & Samali, B. 2013, 'Investigation on Durability of Fibre Reinforced Concrete Exposed to Marine Environment', 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures, Springer, Spain.
The Conference Organisers: UCLM, UNIVERSITY OF CASTILLA- LA MANCHA ESIS, EUROPEAN STRUCTURAL INTEGRITY SOCIETY SEIE-GEF, SPANISH STRUCTURAL INTEGRITY SOCIETY RILEM, INTERNATIONAL UNION OF LABORATORIES AND EXPERTS IN CONSTRUCTION MATERIALS, SYSTEMS AND STRUCTURES
Nabavi, S., Nejadi, S. & Samali, B. 2013, 'PERFORMANCE OF POLYPROPYLENE FIBRE REINFORCED CONCRETE EXPOSED TO SEVERE ENVIRONMENT', First International Conference on Concrete Sustainability, Japan Concrete Engineering Society, Tokyo, Japan.
This paper presents an experimental investigation on mechanical properties and durability assessment of fibre reinforced concrete (FRC) exposed to harsh environment. Mechanical properties include compressive strength, flexural strength and toughness of concrete. Durability assessment is carried out based on corrosion time of embedded steel bar in concrete beam specimen exposed to simulated marine environment for 24 months and utilizing accelerated chloride-induced corrosion test. Results show that the using fibres in concrete not only improve the mechanical properties of concrete but also enhance the durability of concrete.
Shrestha, R., Kabir, M.I. & Samali, B. 2013, 'Experimental study on durability of CFRP-concrete bond subjected to temperature, humidity and outdoor environment', 4th Asia-Pacific Conference on FRP in Structures, Swineburne University of Technology, Melbourne.
This paper presents experimental results and observations to-date of an ongoing research undertaken to investigate the long-term behaviour of bond between externally bonded Carbon Fibre Reinforced polymer (CFRP) and concrete. Carbon FRP strips were externally bonded to concrete prisms and were exposed separately to three different environmental conditions, namely, temperature, humidity and outdoor environment for extended durations. Single-lap-joint shear test (pull-out test) was conducted to investigate bond strengths of control (unexposed) and exposed specimens. Moreover, material characterisation of concrete cylinders and CFRP control and exposed coupons was carried out to observe the changes of mechanical properties with the time of exposure. Finally, experimental results of exposed specimens were compared to those of control specimens in terms of bond strengths and failure modes. Based on the results to-date, the most significant degradation of bond strength was observed in specimens exposed to outdoor environment. Whereas no significant effect of temperature cycles were found provided that the temperature is below the glass transition temperature of epoxy resin.
Vakiloroaya, V., Dibbs, R.L., Ha, Q.P. & Samali, B. 2012, 'Hybrid Solar Air-Conditioner Modelling and Optimal Usage for Energy Saving and Comfort Enhancement', Proceedings of The Second International Conference on Building Energy and Environment, COBEE, Colorado USA, pp. 711-718.
This paper addresses the problem of reducing energy consumption in buildings by using a new hybrid solar-assisted air conditioning (HSAC) system taking into account indoor air quality. Based on the refined models of system components, the influence of integrated vacuum solar collector and solar storage tank on the system performance is discussed in terms of energy savings and human comfort. For this purpose, the system is retrofitted with several sensors and datalogger devices to record the system performance data. The mathematical models and experimentally-collected data are coded into a transient simulation tool. The integrated simulation tool is validated through testing conditions during a summer period. Results are provided to show the capability of significantly reducing electricity consumption while ensuring comfort enhancement by using the proposed system.
Tabatabaiefar, S., Fatahi, B. & Samali, B. 2012, 'Effects of soil dynamic properties and bedrock depth on seismic response of building frames incorporation soil-structure interaction', Proceedings of the 5th Asia-Pacific Conference on Unsaturated Soils Theory and Practice, Kasetsart University, Thailand, pp. 597-603.
In this study, a ten storey moment resisting building frame, resting on a shallow foundation,is selected in conjunction with three soil types with the shear wave velocities less than 600m/s, representing classes Ce, De and Ee, according to AS 1170.4. Different bedrock depths including 10m, 20m, and 30 m are employed in the numerical modelling using finite difference software FLAC 2D. Fully nonlinear dynamic analysis under influence of different earthquake records is conducted, and the results of the three different cases are compared and discussed. The results indicate that the dynamic properties of the subsoil such as shear wave velocity as well as bedrock depth play significant roles in seismic response of the building frames under the influence of soil-structure interaction. As the shear wave velocity of the subsoil decreases and bedrock depth increases, lateral deflections and inter-storey drifts of the structures increase. The mentioned effects can change the performance level of the structures from life safe to near collapse or total collapse. Therefore, the conventional design procedure excluding SSI is no longer adequate to guarantee the structural safety for the building frames resting on soft soil deposits.
Fatahi, B., Tabatabaiefar, S., Sadeghi Hokmabadi, A. & Samali, B. 2012, 'Significance of bedrock depth in dynamic soil-structure interaction analysis for moment resisting frames', SECOND INTERNATIONAL CONFERENCE ON PERFORMANCE-BASED DESIGN IN EARTHQUAKE GEOTECHNICAL ENGINEERING, Associazione Geotecnica Italiana - Roma, Italy, pp. 1396-1406.
In this study, a fifteen storey moment resisting building frame, resting on a shallow foundation, is selected in conjunction with two clayey soils with the shear wave velocities less than 600m/s, representing soil classes De and Ee, according to AS 1170.4. Different bedrock depths including 10m, 20m, and 30 m are employed in the numerical modelling using finite difference software FLAC 2D. Fully nonlinear dynamic analysis under the influence of different earthquake records is conducted, and the results of the three different cases are compared and discussed. The results indicate that the dynamic properties of the subsoil such as shear wave velocity as well as bedrock depth play significant roles in seismic response of the building frames under the influence of soil-structure interaction. As the bedrock depth increases, lateral deflections and inter-storey drifts of the structures increase. These effects can change the performance level of structures from life safe to near collapse or total collapse. Therefore, the conventional design procedure excluding SSI is not adequate enough to guarantee the structural safety for the building frames resting on soft soil deposits.
Sadeghi Hokmabadi, A., Fatahi, B., Tabatabaiefar, S. & Samali, B. 2012, 'Effects of soil-pile-structure interaction on seismic response of moment resisting buildings on soft soil', 3rd International Conference on New Developments in Soil Mechanics and Geotechnical Engineering, Near East University Press, Turkey, Turkey, pp. 377-385.
Dynamic response of structures sitting on soft soils is influenced by the soil properties, and the response is significantly different to the fixed base condition owing to the interaction between the ground and the structure, In order to study this effect, a fifteen storey moment resisting building frame, representing a conventional type of regular mid-rise building frame, resting ,on soil type Ee according to Australian Earthquake action code with the shear wave velocity equal to 150 mls is adopted. The numerical analysis using FLAC2D software is carried out for three different cases, namely: (1) fixed-base structure representing the situation excluding the soil-structure interaction (SSI); (2) structure supported by shallow foundation on soft soil; and (3) structure supported by pile foundation in soft soil. Benchmark earthquakes including the 1995 Kobe, the 1994 Northridge, the 1968 Hachinohe, and the 1940 EI Centro earthquakes are adopted. Results indicate that considering soil-structure interaction in both cases with shallow and pile fouudations is vital, and the conventional desigu procedure excluding soil-structure interaction is not adequate to guarantee the structural safety for the moment resisting buildings resting on the soft soil.
Vakiloroaya, V., Ha, Q.P. & Samali, B. 2012, 'Experimental study of anew solar-assisted air-conditioner for performance prediction and energy', Proceedings 7th Australasian Congress on Applied Mechanics (ACAM 7), Engineers Australia, Adelaide Australia, pp. 768-777.
This paper aims to analyse the performance of a new solar-assisted direct expansion airconditioner and to demonstrate its capability of energy savings and ecological conservation. Here, an integrated flat collector storage system as well as an immersed piped coil is equipped with the direct expansion evaporator to raise the superheat temperature entering the variable speed compressor, causing a smaller duty cycle of the compressor and a slight increase in itssuction pressure, and hence, reduce its energy consumption. Water in the flat solar collector is in contact with the collectors absorbing surface and therefore, heat is transferred to the water and then to the refrigerant in the immersed heat exchanger. Once the room has achieved its desired temperature, the compressor turns off while room cooling will continue until the refrigerant pressure within the circulation loop fails to maintain the desired temperature. The system advantage is that heat can be imparted into the refrigerant via the flat plate collector, so the compressor can remain off longer. This process justifies up to 40% energy savings. Mathematical models will be derived for the system components. These models are then validated against by using experimental data. For this, the system is equipped with several sensors and data-loggers. The models are coded into a transient simulation tool using FORTRAN. Predictions from the model are obtained over a very wide range of operating conditions and exhibit a good coincidence with experimental results. They serve to determine the principal parameters that remain most effective in performance enhancement in terms of reduction of energy consumption and greenhouse gas emission.
Rajabi, A., Valipour Goudarzi, H., Samali, B. & Foster, S. 2012, 'Application of externally post-tensioned FRP bars for strengthening reinforced concrete members', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 145-148.
The volume and weight of heavy vehicles using national road networks has been increasing over the last few decades. At the same time, more than half of the bridges around the world are over forty years old and deterioration of the existing bridges due to increasing traffic loads, adverse environmental conditions, fatigue and structural aging is becoming a major problem. Consequently, restoring and increasing the capacity of bridges and extending their serviceable life by using cost-effective strengthening techniques which ensure minimal traffic disruption, will be of vital importance for protecting the transport system. External post-tensioning is one of the best methods for rehabilitation of the reinforced concrete members owing to speed of construction and minimal disruption to traffic load. However, less attention has been paid to application of external post-tensioning for strengthening reinforced concrete bridge pier. Accordingly, in this paper the application of external posttensioning for strengthening reinforced concrete members is explored. In particular, a detailed nonlinear finite element model is developed and the feasibility of using post-tensioned FRP bars for strengthening a reinforced concrete beam is assessed. To evaluate the efficiency of this system, the results are compared to another finite element model, simulating RC beams strengthened with externally bonded FRP sheets. The flexural and shear strength enhancement achieved by these systems of external post-tensioning is calculated. For the case considered in this paper, application of external post-tensioning can increase the ultimate loading capacity of member by 60% depending on magnitude of post-tensioning forces.
Huang, S., Li, J., Samali, B. & Zobec, M. 2012, 'An experimental investigation of a thermal break composite facade mullion section', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 513-517.
This paper presents the experimental investigation into the behaviour of a typical thermal break composite faade mullion section under quasi-static loadings at various temperatures. Transverse tensile tests and shear tests were carried out according to the requirements of EN14024. Standard specimens specified by this standard were tested to determine characteristic shear strength and transverse tensile strength, as well as the elasticity constant. Tests were carried out at room temperature (23C), low temperature (20C) and high temperature (80C). Test results of shear strength and transverse tensile strength at various temperatures were presented in the graphs. These graphs showed both shear and tensile strength decreased with increased temperature under quasi-static loadings, as well as connectivity constant.
Ghosni, N., Vessalas, K. & Samali, B. 2012, 'Evaluation of fresh properties effect on the compressive strength of polypropylene fibre reinforced polymer modified concrete', From Materials to Structures: Advancement through Innovation - PROCEEDINGS OF THE 22ND AUSTRALASIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, CRC PRESS / BALKEMA, UK, pp. 1123-1127.
Investigations on the characteristics of Fibre Reinforced Concrete (FRC) have gained momentum in the last fewdecades. Employing suitable polymeric fibres and additives in concrete to improve its performance is an important consideration in the construction industry. This research aims to investigative the effect of polypropylene (PP) fibre volume percentage within the concrete mix with and without the presence of polymeric materials on the rheological properties of concrete and its behaviour under compression. PP fibres exhibit low elastic modulus, high elongation and are of low cost, making these fibres most suitable for inclusion in Polymer Modified Concrete (PMC). Traditionally, PP fibres are used in concrete to reduce plastic shrinkage and micro cracking. Accompanying PP fibre additions to PMCs are often styrene butadiene (SB) copolymer latex additions; used to improve the bonding of PP fibres in the cementing matrix. This paper reports on the findings of using different percentages of PP fibres with PMCs incorporating 10% SB latex and 30% fly ash (FA) for partial replacement of Portland cement. Slump, mass per unit volume, air content, high range water reducer agents amount and compressive strength, will be assessed and compared to plain concrete devoid of PP fibre, SB latex and FA additions, after period of curing applied at 7, 28 and 56 days of ageing.
Zabihi, Z., Crews, K.I., Samali, B., S, R. & Gerber, C. 2012, 'Serviceability and ultimate performance of long span timber floor modules', World Conference on Timber Engineering (WCTE 2012), Curran association, Auckland, New Zealand, pp. 121-122.
This paper presents the results of the tests conducted on LVL timber floor modules, with overall lengths of 6.3 m and 8.4 m (6m and 8m clear span, respectively), under serviceable load, as well as the results of 3 destructive tests conducted on 8m clear span LVL timber modules. All serviceability and destructive tests are conducted under four point bending load, and the performance of these long span timber only? floor modules are assessed in serviceability and ultimate limit states. The experimental results are also implemented into a Finite Element model and a comparison between the test results and the numerical model is presented.
Movassaghigilani, S., Samali, B. & Ha, Q.P. 2012, 'Smart structures embedded with MR dampers using non-affine Fuzzy Control', From materials to structures: Advancement through innovation, CRC press/Balkema, Netherlands, pp. 475-478.
A five-storey building model is equipped with a pair of MR (magneto-rheological) dampers installed at the last floor. This smart structure is imposed to scaled earthquake records (in this case, El-Centro earthquake). Actuators are installed on the fourth storey where a Fuzzy Logic Controller is used to deal with the non-affine nonlinear dynamics encountered. The aim of this work is to mitigate the structures vibration due to external excitations via the Fuzzy Logic Controller and the MR damper installed. In the end, the controlled case (structure equipped with MR dampers and Fuzzy Logic Controller) is compared with the uncontrolled case. Simulation results show considerable reductions of the seismic vibration of the structure while the damper current applied is within its working range.
Vessali, N., Valipour Goudarzi, H. & Samali, B. 2012, 'NUMERICAL CHALLENGING OF CAPTURING MEMBRANE ACTION IN REINFORCED CONCRETE BEAMS AND ONE-WAY SLABS', 6th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012), Vienna University of Technology, Vienna, Austria.
Vessali, N., Valipour Goudarzi, H., Samali, B. & Foster, S. 2012, 'Investigating the Arching Action in Reinforced Concrete Beams', 22nd Australian Conference on the Mechanics of Structures and Materials (ACMSM22), University of Technology Sydney (UTS) and The University of New South Wlase (UNSW), Sydney, Australia.
Tat, T., Samali, B. & Shrestha, R. 2011, 'Repair and strengthening of LVL beams with carbon FRP', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), CRC Press/Balkema, The Netherlands, pp. 921-925.
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Existing timber structures may require repair or strengthening due to reasons such as age-related deterioration, damage caused by overloading, design deficiencies due to changes in design codes and increases in loading due to functional changes. Fibre reinforced polymer (FRP) composites feature properties which make them ideal for repair and strengthening purposes, Past research has focused on the use ofFRP on timber primarily for strengthening purposes, Less emphasis has been placed on the use ofFRP to repair damaged timber members. This paper presents the results from a preliminary investigation on laminated veneer lumber (LVL) beams either repaired or strengthened with carbon FRP. The test results indicated that FRP strengthening allowed the repaired specimens to recover up to 68% of their original strength, while the strengthened specimen showed an improvement in ductility.
Zabihi, Z., Crews, K.I. & Samali, B. 2011, 'Modern trends in long span timber flooring systems', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), CRC Press/Balkema, The Netherlands, pp. 903-907.
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With the advent of other types of flooring systems utilising stronger materials and higher performance, timber flooring has been mainly restricted to domestic applications. However, the advent of engineered wood products (EWP's) such as LVL and glulam as well as a new generation of adhesives has provided the means to fabricate large section, long spanning structural members with equal structural properties to that of steel or concrete used in the same applications. On the other hand, timber is the only structural material that is truly renewable and sustainable, and timber buildings result in lower CO2 emissions, therefore, timber structures have attracted a great deal of renewed interest. In this paper, modern trends and approaches used in timber flooring systems worldwide is presented with comments regarding each system's pros and cons, design criteria and requirements. Systems with potential suitability for Australia and New Zealand for non-residential/commercial applications are also discussed.
Li, Y., Li, J. & Samali, B. 2011, 'Design of new generation magnetorheological pins', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australian Conference on the Mechanics of Structures and Materials, pp. 807-812.
Recently, research and development of smart materials and structures for civil engineering applications have attracted increasing attentions from researchers around theworld. Smart devices can be incorporated into civil structures as smart structural members with intelligent and controllable capacities for optimally detecting and reacting to the internal and external changes.Within the smart devices, magnetorheological (MR) based devices are one of the most promising smart devices to be considered for civil structures. This paper presents a novel design of a new-generation MR pin joint with high-torque capacity. An innovative design and analysis of MR pin with radial slots at the surface of the rotary plate is proposed. Theoretical modelling is undertaken based on the material, mechanical and magnetic analyses. Parametric analysis is conducted to optimise the shape, width and depth of the slots to best accommodate the design objectives. 2011 Taylor & Francis Group, London.
Dackermann, U., Li, J. & Samali, B. 2011, 'Identification of added mass on a two-storey framed structure utilising FRFs and ANNs', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), CRC Press/Balkema, The Netherlands, pp. 757-762.
This paper presents a vibration~based damage detection method that utilises frequency response functions (FRFs) to identify added mass on a two-storey framed structure. Added mass is used to simulate frequency changes due to structural damage. Artificial neural networks (ANNs) are employed to map changes in FRFs to locations of the added mass. In order to obtain suitable inputs for neural network training, principal component analysis (PCA) techniques are adopted to reduce the size of the FRF data and to filter noise. A hierarchy of neural network ensembles is used to take advantage of individual measurement characteristics from different sensors. The method is tested on laboratory and numerical models of a two-storey framed structure. From the two kinds of structures, FRF data are determined and compressed utilising PCA techniques. The PCAreduced FRFs are then used as input patterns for training and testing of ANN ensembles predicting different locations of added mass.
Samali, B., Crews, K.I., Aboura, K., Wije, A. & Manamperi, P. 2011, 'A system for bridge network condition assessment and prediction', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), CRC Press/Balkema, The Netherlands, pp. 739-744.
Traditionally, bridge management systems were designed using a Markov chain decision model. Based on the analysis of 15 years of bridge inspection data, we apply the gamma process instead, After extracting all relevant information, enough data was collected on the condition paths of elements to build a deterioration model. The element conditions follow a time period in full condition then start deteriorating. We consider a random variable for the last time the condition was observed to be 100%. We consider the stochastic deterioration process that follows. The amalgamation of the two part process through probabilistic arguments creates a new stochastic process. The novel stochastic process characteristics are derived through the data to provide a predictive model for the element, bridge and network conditions. We showcase a software solution for bridge network condition assessment, monitoring and prediction.
Rijal, R., Samali, B. & Crews, K.I. 2011, 'Dynamic performance of timber-concrete composite flooring systems', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), CRC Press/Balkema, The Netherlands, pp. 315-319.
Long span and light weight floor construction in recent times has led to increased concerns on the dynamic issues with the flooring systems. Therefore, there is a growing need for measurement of dynamic characteristics such as fundamental natural frequency, damping ratio, and mode shapes of floor systems to investigate their behaviour. A combination of timber and concrete has been extensively used to construct floors over the past three decades to resolve most of the issues such as vibration and acoustic encountered in full timber flooring systems. his paper presents the results such as fundamental natural frequency, damping ratio and composite action index from dynamic investigation on four TCC beams with identical geometry but with different connection systems. Initially all the beams were excited by instrumented hammer and free vibration responses were recorded. The connection systems tested included bird-mouth notch with coach screw, nonnal and SFS screws without any notches.
Samali, B., Li, J., Crews, K.I. & Choi, F. 2011, 'Damage evaluation of a repaired timber beam using modal-based method', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), CRC Press/Balkema, The Netherlands, pp. 751-755.
For bridge structures, global damage evaluation and structural health monitoring using modal based damage identification methods have dominated recent worldwide research. However, to date there are few works reported on the effectiveness of the methods to evaluate the new conditions after the damaged structures have been repaired. In this paper, a modal based damage identification method for localisation of damage in a timber beam, utilising modal data from before and after damage as well as after repair, is presented based on expenmental resul!s. The method employs modal parameters that monitor changes in modal strain energy of damaged and repaired beams with respect to the undamaged one. Experimental modal analysis is used in the experimental work to acquire the modal parameters required by the method. The study aims to investigate the capability and limitations of the proposed method for identifying locations of damage in damaged and repaired timber structures.
Pun, R., Samali, B. & Shrestha, B. 2011, 'Major factors in reinforcing stone masonry for sustainable construction practice', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), CRC Press/Balkema, The Netherlands, pp. 547-552.
In this paper, common deficiencies in traditional stone masonry buildings for seismic loading are reviewed along with current practice of reinforcing new buildings and strengthening existing buildings. Major factors to be considered in reinforcing the stone masonry for its sustainability are discussed. Also, a need for reducing the gaps in field implementation is addressed.
Samali, B., Fatahi, B. & Tabatabaiefar, S. 2011, 'Seismic behaviour of concrete moment resisting buildings on soft soil considering soil-structure interaction', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), CRC Press/Balkema, The Netherlands, pp. 407-412.
In this study, the effects of soil-structure interaction (SSI) on the seismic behaviour of reinforced concrete moment resisting building frames are studied using finite difference method. Two types of mid-rise structures, consisting of 5 and 15 stories on soft soil, are selected and analysed. The above mentioned frames are analysed under two different boundary conditions: (i) fixed-base (no soil-structure interaction), and (ii) considering soil-structure interaction. To model soil-structure interaction, the soil medium considering soil's non-linear damping and plasticity with interface elements between soil and structure is included. The results of the analyses in terms of structural forces and lateral displacements for the above mentioned boundary conditions for different earthquakes are compared. It is observed that lateral deflections and drifts ofthe structures increase when SSI is included.
Tabatabaiefar, S., Fatahi, B. & Samali, B. 2011, 'Effects of Dynamic Soil-Structure Interaction on Performance Level of Moment Resisting Buildings Resting on Different Types of Soil', Proceedings of the 2011 Pacific Conference on Earthquake Engineering (PCEE), New Zealand Society for Earthquake Engineering Inc., New Zealand, pp. 1-8.
In this study, two structural models comprising five and fifteen storey moment resisting building frames are selected in conjunction with three different soil deposits with shear wave velocity less than 600m/s. The design sections are defined after applying dynamic nonlinear time history analysis based on inelastic design procedure using elastic-perfectly plastic behaviour of structural elements. These frames are modelled and analysed employing Finite Difference approach using FLAC 2D software under two different boundary conditions namely fixed-base (no soil-structure interaction), and considering soil-structure interaction. Fully nonlinear dynamic analyses under the influence of different earthquake records are conducted and the results of inelastic behaviour of the structural models are compared. The results indicate that the inter-storey drifts of the structural models resting on soil types De and Ee (according to the Australian standard) substantially increase when soil-structure interaction is considered for the above mentioned soil types. Performance levels of the structures change from life safe to near collapse when dynamic soil-structure interaction is incorporated. Therefore, the conventional inelastic design procedure excluding SSI is no longer adequate to guarantee the structural safety for the building frames resting on soft soil deposits.
Fatahi, B., Tabatabaiefar, S. & Samali, B. 2011, 'Performance Based Assessment of Dynamic Soil-Structure Interaction Effects on Seismic Response of Building Frames', PROCEEDINGS OF GEORISK 2011 - Geotechnical Risk Assessment & Management (Geotechnical Special Publication No. 224), American Society of Civil Engineers (ASCE), USA, pp. 344-351.
Soil-Structure Interaction (SSI) has progressed rapidly in the second half of 20th century stimulated mainly by requirements of the nuclear power and offshore industries to improve the seismic safety. In this study, a fifteen storey moment resisting building frame is selected in conjunction with three different soil deposits with shear wave velocity less than 600m/s. The design sections are defined after applying dynamic nonlinear time history analysis based on inelastic design procedure using elastic-perfectly plastic behaviour of structural elements. These frames are modelled and analysed employing Finite Difference approach using FLAC 2D software under two different boundary conditions, namely fixed-base (no soil-structure interaction), and considering soil-structure interaction. Fully nonlinear dynamic analyses under the influence of different earthquake records are conducted and the results of inelastic behaviour of the structural model are compared. Variations of the shear modulus ratio with the shear strain are included in the nonlinear dynamic analysis. The results indicate that the inter-storey drifts of the structural model resting on soil types De and Ee (according to the Australian standard) substantially increase when soil-structure interaction is considered for the above mentioned soil types. Performance levels of the structures change from life safe to near collapse when dynamic soil-structure interaction is incorporated. Therefore, the conventional inelastic design procedure excluding SSI is no longer adequate to guarantee the structural safety for the building frames resting on soft soil deposits. Design engineers need to address the effects of dynamic SSI precisely in their design especially for construction projects on soft soils.
Dackermann, U., Li, J. & Samali, B. 2011, 'Damage Identification on a Numerical Two-Storey Framed Structure using Ambient Vibration Response Analysis and Artificial Neural Networks', Proceeding of The 14th Asia Pacific Conferance, The Hong Kong Polytechnic University, Hong Kong, pp. 338-347.
This paper presents a damage identification method based on ambient floor vibration measurements in multi-storey buildings. The proposed method uses ambient response vibration data to fannulate a damage index based on Frequency Response Functions (FRFs), which is used as input parameter to artificial neural networks (ANNs), to identify locations and severities of damage in a two-storey framed structure. By adopting principal component analysis (PCA) techniques, the Size of the derived damage index is reduced in order to obtain suitable patterns for ANN training. A hierarchy of neural network ensembles is designed to take advantage of individual characteristics of measurements from different floor locations. The proposed method is tested on finite element models of a complex two-storey framed structure inflicted with notch-type damage of different locations and severities (in total six damage cases). The results of the study show that the proposed algorithm is capable of accurately and reliably identifying damage in complex multi-storey structures based on response-only ambient floor vibration measurements.
Zad, A., Li, J., Samali, B. & Crews, K. 2011, 'Finite element evaluation of Non-Destructive Testing methods for embedded timber poles in service', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australian Conference on the Mechanics of Structures and Materials, pp. 909-914.
This paper presents the results of numerical evaluation of surface Non-Destructive Testing methods for embedded timber poles in service. Main objective of the study is to investigate the influence of factors such as different boundary conditions, geotechnical conditions and material defects and imperfections of embedded timber poles, on reliability and accuracy of the prediction or evaluation using surface NDT. Firstly, the numerical evaluation of a free-end timber pole without embedmentwas conducted to gain an understanding of the behaviour of stress waves in timber poles in relation to selected surface NDT methods. Then the embedded timber poles are modelled to include effects of geotechnical conditions as in-service poles. Two types of typical decay patterns are simulated to study the effect of defect/damage on the Non-Destructive Testing results. Finally, the numerical results are compared with field test results obtained from field testing in Victoria. 2011 Taylor & Francis Group, London.
Vakiloroaya, V., Samali, B., Madadnia, J. & Ha, Q.P. 2011, 'Component-Wise Optimization for a Commercial Central Cooling Plant', IECON 2011: 37TH ANNUAL CONFERENCE ON IEEE INDUSTRIAL ELECTRONICS SOCIETY, IEEE.
Vakiloroaya, V., Khatibi, M., Ha, Q.P. & Samali, B. 2011, 'An Optimal Control Strategy For Water-Cooled Direct Expansion System In Real-World Application', Proceedings of the 2011 International Conference on Measurement and Control Engineering, ASME Press, 3 Park Avenue, New York, USA, pp. 31-37.
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In this paper, the optimization-simulation approach based on Lagrange multiplier method is proposed to investigate energy saving potential of a watercooled direct expansion (DX) cooling plant by refining the model of the HVAC system components and deriving optimal conditions for their operation subject to technical constraints. An actual water-cooled DX rooftop package of a realworld commercial building in hot and dry climate conditions is used for experimental data collection, modeling and strategy testing. Both inputs and outputs are measured from the field monitoring in one summer month. Based on the mathematical models and using collected data, modules incorporating the proposed optimal control strategy for the water-cooled DX air conditioning system with variable refrigerant flow rate are developed and embedded in a transient simulation software package. Simulation results are provided to show possibility of significant energy saving and comfort enhancement by implementing proposed optimal control strategy.
Vakiloroaya, V., Khatibi, M., Ha, Q.P. & Samali, B. 2011, 'New Integrated Hybrid Evaporative Cooling System for HVAC Energy Efficiency Improvement', SI International 2011 Proceedings- The Fourth Symposium on System Integration, IEEE, Kyoto Japan, pp. 772-778.
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Cooling systems in buildings are required to be more energy-efficient while maintaining the standard air quality. The aim of this paper is to explore the potential of reducing the energy consumption of a central air-conditioned building taking into account comfort conditions. For this, we propose a new hybrid evaporative cooling system for HVAC efficiency improvement. The integrated system will be modeled and analyzed to accomplish the energy conservation and thermal comfort objectives. Comparisons of the proposed hybrid evaporative cooling approach with current technologies are included to show its advantages. To investigate the potential of energy savings and air quality, a real-world commercial building, located in a hot and dry climate region, together with its central cooling plant is used in the case study. The energy consumption and relevant data of the existing central cooling plant are acquired in a typical summer week. The performance with different cooling systems is simulated by using a transient simulation software package. New modules for the proposed system are developed by using collected experimental data and implemented with the transient tool. Results show that more than 52% power savings can be obtained by this system while maintaining the predicted mean vote (PMV) between -1 to +1 for most of summer time.
Dackermann, U., Li, J., Samali, B., Choi, F. & Crews, K.I. 2011, 'Damage Severity Assessment of Timber Bridges using Frequency Response Functions (FRFs) and Artificial Neural Networks (ANNs)', International Conference on Structural Health Assessment of Timber Structures, Laboratorio Nacional de Engenharia Civil, Lisboa, Portugal, pp. 63-71.
This paper presents a novel vibration-based technique that utilises changes in frequency response functions (FRFs) to assess advancement of damage in timber bridges. In the proposed method, damage patterns embedded in FRF data are extracted and analysed by using a combination of principal component analysis (PCA) and artificial neural network (ANN) techniques for estimation of severity levels of damage. To demonstrate the method, it is applied to a laboratory four-girder timber bridge, which is gradually inflicted with accumulative damage at different locations and severities. To extract damage features in FRFs and to compress the large size of FRF data, FRFs are transferred to the principal component space adopting PCA techniques. PCA-compressed FRF data are then used as inputs to ANNs to identify severities of damage. The excellent severity predictions obtained from the ANNs show that FRF data can potentially be very good indicators for the assessment of damage advancements in timber bridges.
Liu, J., Ding, G.K. & Samali, B. 2011, 'Quantifying and assessing impacts of building processes in a triple bottom line appraoch', World Sustainable Building Conference, Finish Association of Civil Engineers RIL & VTT Technical Research Centre of Finland, Helsinki, Finland, pp. 554-563.
The paper is based on a research project undertaken by the University of Technology, Sydney in examining the integration of economic, social and environmental considerations throughout the building process of a development. The project comprises the first stage, a literature review and model development, followed by the second stage, model implementation through case studies. The paper presents the first stage of the research project in a literature review and model development. The paper reviews the current application of environmental building assessment tools and their impacts on the construction industry. The importance of building process in environmental assessment is also indicated. The paper also seeks to analyze building performance using a triple bottom line approach on a life cycle perspective. The major activities in the building process are identified and presented on how they influence sustainable performance. Finally the paper presents a model that combines economic, social and environmental assessments into a single indicator to aid decision making.
Subhani, S., Li, J., Samali, B. & Dackermann, U. 2011, 'Determinations of Stress Wave Velocity in a Timber Pole using Wavelet Transform', Proceeding of The 14th Asia Pacific Conferance, The Hong Kong Polytechnic University, Hong Kong, pp. 222-231.
This paper presents an application of Wavelet Transform (WT) for determination of stress wave velocity for Non-destructive Testing of timber utility poles in service. For surface Non-destructive Testing (NDT), the hammer impact, which produces generally broadband frequency excitation, is used to generate stress wave. Moreover, due to practicality the impact location for field testing of a utility pole is on the side of the pole and 1.5 m above ground level. And the geometry of utility pole could not guarantee non-dispersive longitudinal wave. All of these issues have resulted in lack of accuracy and reliability of results from surface NDT in field testing. In recognition of such problem, this research explores methods to reliably calculate desired wave velocity by isolating wave mode and studying dispersive nature of utility pole. Fast Fourier Transform (FFT) is firstly conducted to determine the suitable frequency from a stress wave data. Then WT is applied on the wave data mentioned to perform time-frequency analysis. Velocity can be determined by time history data of desired frequency from WT results which will be compared with the available analytical solution for longitudinal wave velocity. The results of the investigation showed that wavelet transform analysis can be a reliable signal processing tool for non-destructive testing in terms of velocity determination, which in turn also helps to determine the embedded length of the timber pole.
Samali, B., Jinwuth, W., Heathcote, K.A. & Wang, C.C. 2011, 'Seismic Capacity Comparison between Square and Circular Plan Adobe Construction', Procedia Engineering, The Proceedings of the Twelfth East Asia-Pacific Conference on Structural Engineering and Construction EASEC12, Elsevier, Amsterdam, The Netherlands, pp. 2103-2108.
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Unreinforced adobe or mud-brick structures have in the past suffered severe damage from seismic forces and have caused a vast number of deaths. However, a number of adobe buildings located in seismic regions have performed well under several seismic events. Most of these traditional buildings shapes are symmetrical which has significant bearing on the performance of the building during strong earthquakes. This paper presents an experimental comparison between two symmetrical shapes, i.e., a square and a circular model of unreinforced adobe walls. One-third scale models were built and tested using a static tilt test for seismic performance evaluation of both structures. The adobe house models were subjected to a constant acceleration when tilted on a tilt-up table. The lateral component of model weight was used as a parameter to quantify the maximum seismic force for each model. The paper describes the configuration of both specimens and testing method. The results of these comparative experiments indicated a better performance of the circular structure. There are simple and effective solutions for construction of new adobe buildings located in seismic hazard areas which can assist in decreasing damage and death.
Samali, B., Zahrai, S.M., Vrcelj, Z. & Abbasi, S. 2011, 'Effectiveness of variably tuned liquid damper in suppressing dynamic excitation', Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), CRC Press/Balkema, The Netherlands, pp. 297-301.
Tuned liquid damper (TLD) is a special type of auxiliary damping device which relies on the sloshing of a liquid (water) in a container to counteract the forces acting on the structure. In this paper a new kind ofTLD with some movable baffles is experimentally studied. These movable baffles change the dynamic characteristics of the TLD, specially frequency and damping. Response of a five storey benchmark building was utilized to investigate the efficiency of variably tuned liquid damper (VTLD) under dynamic excitations. By observing the performance ofVTLD this study investigates the effects of probable mistuning by changing the depth of water and frequency ratio as welL The damping ratios of the building in several conditions of baffles angles were evaluated using logarithmic decrement technique. The results show that one can enhance the performance of TLDs by installing some movable baffles and overcome probable mistuning of the TLD.
Aoki, Y., Samali, B., Saleh, A. & Valipour Goudarzi, H. 2011, 'Impact of sudden failure of cables on the dynamic performance of a cable-stayed bridge', The Austroads 8th Bridge Conferences - Sustainable Bridges: The Thread of Society - proceedings Volume II, Austroads Incorporated, Australia, pp. 310-321.
In cable stayed bridges corrosion and fatigue as well as extreme loadings such as earthquake, lightning strike and blast may lead to loss of cables. The vulnerability of cable stayed bridges for such cable loss scenarios has not been thoroughly investigated yet and is not considered in the current design practice. Accordingly, in this paper a primary study on vulnerability of cable stayed bridges against such extreme scenarios is undertaken. A two-dimensional Finite Element (FE) model of a cable-stayed bridge is developed in ANSYS. The mid-span of the bridge studied in this paper is 600 meter long and made of a steel box. The bridge is supported by two 140 meter tall steel towers and 56 steel cables. The bridge is analysed for two different cable loss scenarios and the global response of the structure (i.e. deformation of the bridge, bending moment at mid-span of the deck and the base of the tower, and axial force for deck and each cable) following the cable loss scenarios are studied. Further, dynamic amplification factors (DAF) for deflections and internal forces are determined by comparing the results of static analysis with the results obtained from transient dynamic analysis.
Askari, M., Li, J. & Samali, B. 2011, 'Semi-Active LQG Control of Seismically Excited Nonlinear Buildings using Optimal Takagi-Sugeno Inverse Model of MR Dampers', Procedia Engineering: The Proceedings of the Twelfth East Asia-Pacific Conference on Structural Engineering and Construction EASEC12, Elsevier, The Netherlands, pp. 2765-2772.
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A novel semi-active control method for a seismically excited nonlinear benchmark building equipped with magnetorheological (MR) dampers is presented and evaluated in this paper. While Linear Quadratic Gaussian (LQG) controller is designed to estimate the optimal control force of a MR damper, the required voltage input for the damper to produce such control force is achieved by a proposed optimal Takagi- Sogeno(T-S) fuzzy inverse model. The proposed T-S fuzzy inverse model of dampers is derived using subtractive clustering, non-dominated sorting genetic algorithm II (NSGAII) and adaptive neuro-fuzzy inference systems (ANFIS). The effectiveness of this strategy is illustrated and verified using simulated response of a 20-storey full-scale nonlinear benchmark building excited by several historical earthquake records. The designed semi-active system is compared with the performances of active control as well as clipped optimal control (COC) systems, which are based on the same nominal controller as is used in this study. The results are discussed based on the evaluation criteria suggested for the benchmark problem by International Association for Structural Control and Monitoring (IASCM) for comparison with other algorithms and demonstrate the superiority of this scheme over other strategies.
Fatahi, B., Tabatabaiefar, S. & Samali, B. 2010, 'Influence Of Soil Characteristics On Seismic Response Of Mid-Rise Moment Resisting Buildings Considering Soil-Structure Interaction', Seismic Engineering Design for Management of Geohazards - Proceedings of the 2010 Symposium, The Australian Geomechanics Society, NSW, Australia, pp. 67-74.
In this study, a fifteen storey moment resisting building frame, representing the conventional types of regular mid-rise building frames, resting on a shallow foundation, is selected in conjunction with three soil types with the shear wave velocity less that 600m/s, representing classes Ce, De and Ee, according to AS 1170.4. Characteristics of the employed soils have been extracted from the available geotechnical investigation reports of various projects. Furthermore, the structure is modelled considering the three mentioned types of the subsoil medium underneath employing the Finite Difference approach using FLAC 2D software. Three strong ground motion records adopted by the international community as benchmark earthquakes are used. These are the 1968 Hachinohe, the 1995 Kobe and the 1994 Northridge earthquakes. Fully nonlinear dynamic analysis under influence of different earthquake records is conducted, and the results of the three different cases are compared and discussed. The results indicate that the dynamic properties of the subsoil play a significant role in seismic response of the building frames under the influence of soil-structure interaction. As the shear wave velocity of the subsoil decreases, lateral deflections and inter-storey drifts of the structures increase which can change the performance level of the structures from life safe to near collapse or total collapse.
Zheng, L., He, S., Samali, B. & Yang, L. 2010, 'Accuracy Enhancement for License Plate Recognition', Proceedings - 10th IEEE International Conference on Computer and Information Technology (CIT 2010), IEEE Computer Society, Bradford, West Yorkshire UK, pp. 511-516.
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Automatic License Plate Recognition is useful for real time traffice management and surveillance. License plate recognition usually contains two steps, namely license plate detection/localization and character recognition. Recognizing character in a license plate is very difficult task due to poor illumination conditions and rapid motion of vehicles. When using an OCR for character recognition, it is crucial to correctly remove the license plate boundaries after the step for license plate detection. No matter which OCRs are used, the recognition accuracy will be significantly reduced if the boundaries are not properly removed. This paper presents an efficient algorithm for non character area removal. The algorithm is based on the license plates detected using an AdaBoost algorithm. Then it follows the steps of character height estimation, character width estimation, segmentation and block identification. The algorithm is efficient and can be applied in real time applications. The experiments are performed using OCR software for character recognition. It is shown that much higher recognition accuracy is obtained by gradually removing the license plate boundaries
Tabatabaiefar, S., Samali, B. & Fatahi, B. 2010, 'Effects of Dynamic Soil-Structure Interaction on Inelastic Behaviour of Mid-Rise Moment Resisting Buildings on Soft Soils', AEES Conference 2010 - Australian Earthquake Engineering Society 2010 Conference, Australian Earthquake Engineering Society, Perth, Australia, pp. 1-11.
In this study, a ten storey moment resisting building frame, representing the conventional type of regular mid-rise building frames, resting on shallow foundation, is selected in conjunction with a clayey soil, representing subsoil class Ee, as classified in the AS 1170.4. The structural sections are designed after applying dynamic nonlinear time history analysis, based on both elastic method, and inelastic procedure using elastic-perfectly plastic behaviour of structural elements. The frame sections are modelled and analysed, employing Finite Difference Method using FLAC 2D software under two different boundary conditions: (i) fixed-base (no Soil-Structure Interaction), and (ii) considering Soil-Structure Interaction (SSI). Fully nonlinear dynamic analysis under influence of different earthquake records is conducted and the results of the two different cases for elastic and inelastic behaviour of the structural model are extracted and compared respectively. The results indicate that the lateral deflection increments for both cases are substantially dominating and can change the performance level of the structures from life safe to near collapse or total collapse. Therefore, conventional elastic and inelastic structural analysis methods assuming fixed-base structure may no longer be adequate to guarantee the structural safety. Therefore, considering SSI effects in seismic design of concrete moment resisting building frames resting on soft soil deposit is essential.
Jinwuth, W., Samali, B., Heathcote, K.A. & Wang, C.C. 2010, 'A study into the earthquake resistance of circular adobe buildings using static tilt tests'.
Many unreinforced adobe or mud-brick structures have in the past suffered severe damage from seismic forces and have caused a vast number of deaths. However, some adobe buildings located in seismic regions have performed well under several seismic events. Most of these traditional buildings are symmetrical in shape which has significant bearing on the performance of the buildings during strong earthquakes. Most existing and typical circular adobe houses have performed well in withstanding earthquakes even though some did not have any additional ductile reinforcement. This paper presents the first series of tests conducted to study the performance of unreinforced circular adobe buildings subjected to earthquake forces. Nine small-scale models (1:3 scale) of adobe structures were built with a variety of configurations and roof loads. Static tilt tests were carried out to evaluate the seismic performance of this type of structure. The adobe house models were subjected to a constant acceleration when tilted on a tilt-up table. The lateral component of model weight was used as a parameter to quantify the maximum seismic force for each model. The results were then used to develop a methodology for designing circular adobe buildings to resist earthquakes in specific seismic zones and for specific site conditions.
Tabatabaiefar, S., Fatahi, B. & Samali, B. 2010, 'Seismic Behaviour of Steel Moment Resisting Buildings on Soft Soil Considering Soil-Structure Interaction', Proceeding of the 14 European Conference on Earthquake Engineering 2010, Macedonian Association for Earthquake Engineering (MAEE), Macedonia, pp. 1720-1727.
The 1985 Mexico City and many other recent earthquakes clearly illustrate the importance of local soil properties on the earthquake response of structures. These earthquakes demonstrated that the rock motions could be amplified at the base of the structure. Therefore, there is a strong engineering motivation for a site-dependent dynamic response analysis for many foundations to determine the free-field earthquake motions. The determination of a realistic site-dependent free-field surface motion at the base of the structure can be the most important step in the earthquake resistant design of structures. In this study, the effects of Soil-Structure Interaction on seismic behaviour of steel moment resisting building frames have been studied using Finite Difference Method. Two types of mid-rise structures, including 5 and 15 storey buildings on a soft soil deposit have been selected and analysed under influence of three different earthquake acceleration records. The above mentioned frames been analysed under two different boundary conditions: (i) fixed-base (no soil-structure interaction), and (ii) flexible-base (considering soil-structure interaction). The results of the analyses in terms of structural forces and lateral displacements for the above mentioned boundary conditions have been compared and discussed. It is concluded that the dynamic soil-structure interaction plays a significant role in the seismic behaviour of the mentioned building frames including substantial increment in lateral inter-storey drifts of the structures and changing the performance level of the structures from life safe to near collapse or total collapse. Thus, Considering SSI effects in seismic design of steel moment resisting building frames resting on soft soil deposit is essential.
Aboura, K., Samali, B., Crews, K.I. & Li, J. 2009, 'Stochastic Processes for Modelling Bridge Deterioration', Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, Taylor and Francis Group, London, pp. 533-538.
Traditionally, bridge management systems were designed using Markov chain models.
Manamperi, P., Wije, A., Perumynar, S., Aboura, K., Samali, B. & Crews, K.I. 2009, 'Stochastic Processes for Bridge Deterioration Assessment', 7th Austroads Bridge Conference - Bridges linking communities, Austroads, New Zealands, pp. 1-9.
The Roads and Traffic Authority of NSW (RTA) has over 5000 bridges in the road network under its jurisdiction. These structures were built from different materials, at different times, under different design codes with different articulations and are exposed to different environments. The levels and rate of deterioration of these structures vary greatly and are dependent on the effects of age, environment, magnitude and frequency of heavy traffic and construction quality. These factors make the management of these structures a real challenge to the RTA. In order for the RTA to improve the management of these bridge assets, the RTA is working with the University of Technology Sydney (UTS) to develop a statistical model to predict the future condition of bridges using the condition inspection data collected over the last 15 years. This paper will report on findings of the study conducted to identify a suitable model for prediction of future condition of bridges based on the available inspection data. The gamma process is considered in the development of the predictive model for the life of bridge components. In addition to the gamma process application, observations are made on the distribution of deterioration at different times that could lead to other stochastic processes for modeling time-dependent structural deterioration.
Shrestha, R., Samali, B. & Smith, S.T. 2009, 'Effectiveness of repairing damaged RC beam-column connections with FRP strips', Future in Mechanics of Structures and Materials, Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, Taylor & Francis Group, London, UK, pp. 395-403.
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Dowling, D.M. & Samali, B. 2009, 'Low-Cost and Low-Tech Reinforcement Systems for Improved Earthquake Resistance of Mud Brick Buildings', Proceedings of the Getty Seismic Adobe Project 2006 Colloquium, The Getty Conservation Institute, USA, pp. 23-33.
Traditional, unreinforced adobe mud brick structures are highly susceptible to damage and destruction during seismic events. This vulnerability is evident in historic adobe structures around the world, as well as in traditional adobe homes in developing countries where severe earthquakes repeatedly cause drastic losses of life and livelihood. Adobe research at the University of Technology, Sydney (UTS), Australia, is focused on the development of low-cost, low-tech reinforcement systems for adobe structures. To date, ten U-shaped adobe wall panels and one full model house (1:2 scale) with different reinforcing systems have been subjected to transient dynamic loading using a shake table to evaluate the response to seismic forces. Time-scaled input spectra have been used to ensure dynamic similitude and impart sufficient energy to each structure to induce damaging conditions. The force-displacement characteristics and failure mechanisms of each structure have been studied to determine the resistance capacity of each system. Results indicate that a major improvement in structural performance can be achieved by using stiff external vertical reinforcement (e.g., bamboo), external horizontal reinforcement (e.g., bamboo or wire), and a timber ring/crown beam. This integrated matrix acts to restrain movement and enhance the overall strength of the structure. Tests have shown this system to effectively delay the onset of initial cracking and prevent collapse, even during severe shaking. The proposed system is effective, simple, affordable, and widely adaptable to a variety of materials and local conditions. It can be used for the retrofit-strengthening of existing structures, as well as in new construction. It shows tremendous promise for application in developing countries and for the protection and preservation of historic adobe structures around the world.
Gerber, C., Crews, K.I., Sigrist, C. & Samali, B. 2008, 'A numerical approach for assessing the behaviours of timber stressed panels', Proc. ASEC 2008, The Meeting Planners, Melbourne, pp. 1-11.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2008, 'Non Destructive Testing of a Timber Beam using Vibration-Based Approach', The 9th International Conference on Motion and Vibration Control, Technique Universaetet, Germany.
Dackermann, U., Li, J., Samali, B., Choi, F. & Crews, K.I. 2008, 'Variation-Based Damage Identification in Civil Engineering Structures Utilising Artificial Neural Networks', Proc. Structural Faults & Repairs 2008 12th International Conference, Engineering Technics Press, Endinburgh, pp. 132-132.
He, X., Zheng, L., Wu, Q., Jia, W., Samali, B. & Palaniswami, M. 2008, 'Segmentation of characters on car license plates', Proceedings of the 2008 IEEE 10th Workshop on Multimedia Signal Processing, MMSP 2008, pp. 399-402.
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License plate recognition usually contains three steps, namely license plate detection/localization, character segmentation and character recognition. When reading characters on a license plate one by one after license plate detection step, it is crucial to accurately segment the characters. The segmentation step may be affected by many factors such as license plate boundaries (frames). The recognition accuracy will be significantly reduced if the characters are not properly segmented. This paper presents an efficient algorithm for character segmentation on a license plate. The algorithm follows the step that detects the license plates using an AdaBoost algorithm. It is based on an efficient and accurate skew and slant correction of license plates, and works together with boundary (frame) removal of license plates. The algorithm is efficient and can be applied in real-time applications. The experiments are performed to show the accuracy of segmentation. 2008 IEEE.
Zheng, L., He, X., Wu, Q., Jia, W., Samali, B. & Palaniswami, M. 2008, 'A hierarchically combined classifier for license plate recognition', Proceedings - 2008 IEEE 8th International Conference on Computer and Information Technology, CIT 2008, pp. 372-377.
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High accuracy and fast recognition speed are two requirements for real-time and automatic license plate recognition system. In this paper, we propose a hierarchically combined classifier based on an Inductive Learning Based Method and an SVM-based classification. This approach employs the inductive learning based method to roughly divide all classes into smaller groups. Then the SVM method is used for character classification in individual groups. Both start from a collection of samples of characters from license plates. After a training process using some known samples in advance, the inductive learning rules are extracted for rough classification and the parameters used for SVM-based classification are obtained. Then, a classification tree is constructed for further fast training and testing processes for SVMbased classification. Experimental results for the proposed approach are given. From the experimental results, we can make the conclusion that the hierarchically combined classifier is better than either the inductive learning based classification or the SVMbased classification in terms of error rates and processing speeds. 2008 IEEE.
Wang, Y., Samali, B. & Sri Ravindrarajah, R. 2008, 'Non-destructive damage detection in reinforced concrete beams based on modal strain energy', Proceedings of Australasian structural Engineering Conference, The Meeting Planners, Australia, pp. 1-8.
Wang, Y., Li, J., Samali, B. & Sri Ravindrarajah, R. 2008, 'A New Damage Detection Method for Reinforced Concrete Beams Based on Modal Strain Energy', Proceedings of the 9th International Conference on Motion and Vibration Control, Technische Universitaet Muenchen, Germany, pp. 1-10.
Wang, Y., Samali, B. & Choi, F. 2008, 'A New Non-destructive Damage Detection Method for Reinforced Concrete Beams Based on Modal Strain Energy', Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, CRC Press, London, pp. 773-778.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2008, 'Overview of Dynamic Based Damage Detection for Timber Bridges', On-Site Assessment of Concrete, Masonry and Timber Structures - Volume 2, RILEM Publications, France, pp. 1125-1135.
Asset management of bridges throughout the world faces increasing challenges as a result of aging infrastructure and inadequate funding. Replacement of an old bridge is neither viable nor sustainable in many circumstances. As a consequence, there is an urgent need to develop and utilise state-of-the-art techniques to assess and evaluate the "health state" of existing bridges and to be able to understand and quantify the effects ofdegradation in regard to public safety. This paper presents an overview of experimental work for a project in developing and implementing several dynamic methods for evaluation of damage in timber bridges. The technique of detecting damage involved the use of modal strain energy commonly referred to in the literature as damage index methods. The project started with simple beams subjected to single and multiple damage and then was extended to a scale timber bridge constructed under laboratory conditions. It was found that after modification on the damage index method, it was well suited to detect single and multiple damage scenarios for a one-dimensional beam. For the laboratory bridge, the damage index method developed for plate-like structures was successful in detecting single and multiple damage with an acceptable degree of accuracy.
Gerber, C., Crews, K.I., Sigrist, C. & Samali, B. 2008, 'Timber stressed-skin panels Design Guidelines for Australian Practice', Proc. ASEC2008, The Meeting Planners, Victoria, pp. 1-7.
Li, J., Samali, B. & Xu, Y.L. 2008, 'A new modal based damage detection approach utilising added mass', Futures in Mechanics of Structures and Materials - Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, ACMSM20, pp. 789-793.
To reliably detect structural damage and estimate damage severity at its early stage poses a great challenge to engineering community. Despite a great deal of research and development in the areas of damage detection and health monitoring, there are very few successful applications in real life damage detection in engineering practices. One of the main obstacles for successful application of damage detection algorithms to real life civil infrastructure is the complex nature of structures and the uncertainties associated with modelling and measurement. This paper presents a new modal based damage detection approach aiming to provide an effective means to improve reliability and accuracy of damage detection. The proposed approach requires measurement data from two states of the structure, i.e. data from the structure "as-is" and data from the structure after adding a known mass. By means of experimental modal analysis (EMA), the modal parameters of the structure with and without added mass can be obtained. With modal parameters of the said two states and the known added mass, the proposed method will be able to produce the "in-service" system stiffness matrix. With the element connectivity being known a priori (or assumed reasonably), the "in-service" element stiffness can be obtained. Location of damage as well as damage severity of the structure will therefore be known. Experimental verification of the proposed method was carried out using a three storey shear building model. The experimental results show that the proposed damage detection method is superior in both damage localisation and damage severity estimation. 2009 Taylor & Francis Group, London.
Dackermann, U., Li, J., Samali, B., Choi, F. & Crews, K.I. 2008, 'Experimental Verification of A Vibration-Based Damage Identification Method In A Timber Structure Utilising Neural Network Ensembles', Proc. SACOMATIS 2008, RILEM Publications, France, pp. 1049-1058.
Dackermann, U., Li, J. & Samali, B. 2008, 'Damage Index Method for Damage Identification Utilising Artificial Nerual Networks', Proc. MOVIC 2008, MOVIC, Germany, pp. 1-10.
Dackermann, U. & Samali, B. 2008, 'Damage Identification based on MOdal Strain Energy utilising Nerual Network Ensembles', Proc. ASEC 2008, The Meeting Planners, Victoria, pp. 1-10.
Dackermann, U., Li, J. & Samali, B. 2008, 'Structural damage identification utilising PCA-compressed frequency response functons and neural network ensembles', Future in Mechanics of Structures and Materials, Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, CRC Press, Taylor & Francis Group, London, pp. 803-809.
Samali, B., Li, J. & Aboura, K. 2008, 'Monitoring bridge deterioration using sensors', Proceedings - 3rd International Conference on Broadband Communications, Informatics and Biomedical Applications, BroadCom 2008, pp. 64-69.
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Structural health monitoring is a vital part in the management of bridges, particulary as the structures begin to age. Detecting structural faults through the use of sensors is an emerging field that has seen considerable efforts this past decade. Similarly, the use of sensors in bridge management systems provides valuable data on the condition of bridges and external factors affecting the deterioration of bridges such as the traffic load endured by the structures. We review both cases of visual and vibration based monitoring of bridges and showcase an on-line monitoring system for the collection of traffic information. 2008 IEEE.
Aboura, K., Samali, B., Crews, K. & Li, J. 2008, 'Stochastic deterioration processes for bridge lifetime assessment', Proceedings - 3rd International Conference on Broadband Communications, Informatics and Biomedical Applications, BroadCom 2008, pp. 437-442.
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The Markov chain model can be found in the maintenance and repair problems since the early 60's, is introduced to the maintenance of road infrastructure in the 1980's, and is made to drive the current bridge maintenance optimization systems. While this model results into solvable programming problems and provides a solution, there are a number of criticisms associated with it. In this article, we highlight the shortfalls of the Markov model for bridge infrastructure lifetime assessment and promote the use of stochastic processes. We use examples from a study for the modeling of the condition of bridges that considers more than 15 years of data. We argue for the applicability of the gamma process and other stochastic processes. 2008 IEEE.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2008, 'Overview of Dynamic Based Damage Detection of Timber Bridges', Proceedings of 12th International Conference STRUCTURAL FAULTS & REPAIR-2008, University of Edinburgh, UK, pp. 1-13.
Asset management of bridges throughout the world faces increasing challenges as a result of ageing infrastructure and inadequate funding. Replacement of an old bridge is neither viable nor sustainable in many circumstances. As a consequence, there is an urgent need to develop and utilise state-of-the-art techniques to assess and evaluate the the state of health? of existing bridges and to be able to understand and quantify the effects of degradation in regard to public safety. This paper presents an overview of part of the numerical work for a project recently completed by the authors to develop and implement dynamic methods for evaluation of damage in timber bridges. The damage detection technique involved the use of a modal strain energy based method, commonly referred to in the literature as damage index methods. The project started with simple beams subjected to single and multiple damage scenarios. The research was then extended to a scaled laboratory timber bridge. It was found that with proper modification, the damage index method was well suited to detect single and multiple damage scenarios for a onedimensional beam. For the laboratory timber bridge, the damage index method, developed for plate-like structures, can detect single and multiple damage locations with certain level of errors.
Shrestha, R., Smith, S.T. & Samali, B. 2008, 'Effectiveness of strengthening RC beam-column connections in shear with vertical FRP strips', FRP Composites in Civil Engineering - Proceedings of the 4th International Conference on FRP Composites in Civil Engineering, EMPA-Akademie, Switzerland, pp. 1-6.
Reinforced concrete (RC) connections, designed prior to the implementation of earthquake design standards around the world, may not posses sufficient shear strength to withstand a seismic attack. Such connections will therefore require strengthening. This paper reports the results of tests on two-dimensional RC connections which have been strengthened in shear with externally bonded fiber reinforced polymer (FRP) composite strips. FRP strips are an attractive strengthening solution as they are relatively simple to apply, and in this study they are orientated parallel to the longitudinal axis of the column (i.e. vertical strips). The tests reported in this paper serve to evaluate the effectiveness of the use of vertical FRP strips for strengthening and as a result, the test specimens are heavily instrumented in order to monitor not just the FRP but the connection as a whole. The hierarchy of strength dictates eventual failure in the joint region, even for the FRP strengthened connections, and all test specimens are subjected to monotonic or cyclic loading.
Li, Y., Li, J., Samali, B. & Wang, J. 2008, 'Theoretical and experimental studies on semi-active smart pin joint', Futures in Mechanics of Structures and Materials - Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, ACMSM20, pp. 723-728.
An intelligent structural system equipped with smart structural members that are controllable in real-time is one effective solution to prevent structural damage and failure during hostile dynamic loadings, thereby leading to effective protection of structures and their occupants. The primary purpose of this study is to design, fabricate and characterise a prototype smart member, namely a semi-active magnetorheological (MR) pin joint, through theoretical modelling and experimental investigation. Design of prototype smart pin joints includes theoretical analysis relating to the rotary plate radius, the property of MR fluids and the gap between the rotary plate and the casing based on the requirements of the dynamics of MR pin joints. It is verified that an MR pin joint with a diameter of 180 mm can produce a torque of up to 30 Nm, which is deemed adequate for realisation of the semi-active control for multi-storey building models in the next stage of research. 2009 Taylor & Francis Group, London.
Widjaja, J.H. & Samali, B. 2007, 'Structural System Identification of MR device-plane frame systems', Proceedings of the 19th Australasian Conference on the Mechanics of Structures and Materials - Progress in Mechanics of Structures and Materials, Taylor and Francis, Leiden, Netherlands, pp. 261-266.
This paper presents a simple dynamic identification technique using Fast Fourier Transform (FFT) amd least-square method to respectively estimate the system frequency and damping doefficient together with Coulomb or static friction of Magneto-Rheological (MR) device-plane frame system.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2007, 'Damage Evaluation of a timber Beam Using a Modal-based Method', Proceeding of the 19th Australasian Conference on the Mechanics of Structures and Materials - Progress in Mechanics of Structures and Materials, Taylor and Francis, Leiden, Netherlands, pp. 1005-1010.
Li, J., Choi, F. & Samali, B. 2007, 'Modal-based damage identification methods for plate-like structures', Proceedings of the 19th Australasian Conference on the Mechanics of Structures and Materials - Progress in Mechanics of Structures and Materials, Taylor and Francis, Leiden, Netherlands, pp. 909-914.
Li, J., Samali, B. & Crews, K.I. 2007, 'A cost effective approach for integrity assessment of timber bridges', Proceedings of the 19th Australasian Conference on the Mechanics of Structures and Materials - Progress in Mechanics of Structures and Materials, Taylor and Francis, Leiden, Netherlands, pp. 1037-1042.
Kwok, N., Ha, Q.P. & Samali, B. 2007, 'MR Damper Optimal placement for semi-active control of buildings using an efficient multi-objective binary genetic algorithm', Proceedings of the 24th International Symposium on Automation and Robotics in Construction (ISARC 2007), Lokavani Southern Printers, Chennai, India, pp. 361-367.
Samali, B., Choi, F., Li, J. & Crews, K.I. 2007, 'Experimental investigations on a laboratory timber bridge using Damage Index Method for plate-like structures', Proceedings of the 5th Australasian Congress on Applied Mechanics, ACAM 2007, Engineers Australia, Australia, pp. 114-119.
A great deal of work has been done in the area of damage identification in structures using changes of modal parameters before and after damage. Most of the developments have been based on beam theory and applied to beam-like or truss structures. Few researchers have made contributions to damage identification of plate-like structures employing a damage index method, especially for timber structures. In this paper, experimental investigations on a laboratory timber bridge using damage index method for plate-like structures are reported. Experimental modal analysis was performed to extract essential modal parameters from test data. Mode shape curvatures derived from the mode shapes were utilised in a damage index method for plate-like structures to detect single and two damage scenarios in a timber bridge. The purpose of the study is to explore feasibility of using modal strain energy based methods for damage identification of plate-like structures. The results show that the damage index method for plate-like structures using higher modes provides reasonable damage localisation for single and multiple damage cases.
Nguyen, M.T., Kwok, N.M., Ha, Q.P., Li, J. & Samali, B. 2007, 'Semi-active direct control of civil structure seismic responses using magneto-rheological dampers', Automation and Robotics in Construction - Proceedings of the 24th International Symposium on Automation and Robotics in Construction, pp. 157-162.
As building structures frequently collapse and cause losses of lives and properties, due to excessive vibrations induced during earthquake periods, it is crucial to reduce the structural vibrations. This paper develops a Lyapunov-based controller for Magnetorheological (MR) dampers embedded in building structures to mitigate quake-induced vibrations. In this work, MR dampers are used as semi-active devices, taking the advantages of the fail-safe operation and low power requirement. To enhance the system performance, a Lyapunov-based controller is proposed here for direct control of the supply currents of the MR dampers placed in a multi-storey building. The effectiveness of the proposed technique is verified in simulation by using a ten-storey building model subject to quake-like excitations.
Nguyen, M., Kwok, N., Ha, Q.P. & Samali, B. 2007, 'MR Dampers Optimal Placement for Semi-Active Control Building Using and Efficient Multi-objective Binary Genetic Algorithm', Proceedings of the 24th International Symposium on Automation and Robotics in Construction, Indian Institute of Technology, Madras.
Nguyen, M., Kwok, N., Ha, Q.P., Li, J. & Samali, B. 2007, 'Mitigation of Seismic Responses in Building Structures using Magneto-rheological Dampers', Proceedings of the 24th International Symposium on Automation and Robotics in Construction (ISARC 2007), Indian Institute of Technology Madras, Madras, India.
Gerber, C., Crews, K.I., Sigrist, C. & Samali, B. 2007, 'Assessment of the composite action in timber stressed-skin panels', Proceedings of the 5th Australasian Congress on Applied Mechanics (ACAM 2007), Engineers Australia, Australia, pp. 184-189.
In 2002 a large-scale investigation on timber stressed-skin panel (SSP) decks commenced at the University of Technology, Sydney. 27 full-scale specimens, manufactured according to Australian practices in timber construction, were investigated under bending conditions with various load configurations - series of non-destructive and destructive tests. The tests also considered the effects of boundary conditions such as blocking and the influence of defects. The scope of the test analysis included identifying the serviceability behaviour, the load distribution and the composite properties of SSP structures. This paper focuses on the composite action in SSP systems, which is assessed by analysing the profile of the strain distribution in the composite section. The evaluation of two mathematical methods used to estimate the section characteristics of the SSP specimens are also presented in this paper.
Kwok, N., Nguyen, T., Ha, Q.P., Li, J. & Samali, B. 2006, 'Parameter Identification for a simple MR Damper model using Particle Swarm Optimisation', Disgest Book of the Asia Pacific Symposium on Applied Electromagnetic and Mechanics, UTS, Sydney, Australia, p. 11.
Nguyen, T., Kwok, N., Ha, Q.P., Li, J. & Samali, B. 2006, 'Symmetric Quantized Sliding Model Control for Civil Structures Using Magnetorcheological Dampers', Digest Book of the Asia-Pacific Symposium on Applied Electromagnetics and Mechanics, UTS, Sydney, Australia, p. 47.
Li, J., Samali, B., Crews, K.I., Choi, F., Brown, P.W., Al-Dawod, M. & Shrestha, R. 2006, 'theoretical and Experimental Studies on Assessment of Bridges Using Simple Dynamic Procedures', Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building Into the Future, Tour Hosts Pty Ltd, Australia.
Widjaja, J.H., Samali, B., Li, J. & Reizes, J. 2006, 'Seismic Structural Control Investigations Using a Prototype Magneto-rheological Shear Damper', Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, Tour Hosts Pty Ltd, Austrlaia.
Samali, B., Dowling, D.M. & Li, J. 2006, 'Dynamic Response of U-Shaped Adobe-Mudbrick Wall Units', Austrlaian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building Into the Future, Tour Hosts Pty Ltd, Australia.
Dowling, D.M., Price, H.V. & Samali, B. 2006, 'Shear Strength of Adbobe-Mudbrick Mortar Joints', Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, Tour Hosts Pty Limited, Australia.
Widjaja, J.H. & Samali, B. 2006, 'Dynamic Analysis of "Smart" Pin-Frame System Using Timefrequency Representation of Earthquakes', Proceedings of the Tenth East Asia-Pacific Conference on Structural Engineering and Construction - Supplementary Papers, School of Engineering and Technology, Asian Institute of Technology, Pathumthani, Thailand, pp. 83-88.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2006, 'Impact of Different Numerical Techniques on Damage Identification in Structures', Proceedings of The Tenth East Asia-Pacific Conference on Structural Engineering and Construction - Materials, Experimentation, Maintenance and Rehabilitation, School of Engineering and Technology, Asian Institute of Technology, Pathumthani, Thailand, pp. 111-116.
Li, J., Choi, F., Samali, B. & Crews, K.I. 2006, 'Damage Localisation and Severity Evaluation of a Beam-like timber Structure based on modal strain energy and flexibility approaches', Proceedings of the Eleventh International Conference on Structural Faults and Repair 2006, Engineering Technics Press, Edinburgh, U.K., pp. 1-9.
Li, J., Choi, F., Samali, B. & Crews, K.I. 2006, 'Damage Detection in a Timber Beam', Proceedings of the Eleventh International Conference on Structural Faults and Repair 2006, Engineering Technics Press, Edinburgh, U.K., pp. 1-10.
Widjaja, J.H., Samali, B. & Li, J. 2006, 'The use of Displacement Threshold for Switching Frequency Strategy for Structural Vibration Mitigation', The 8th International Conference on Motion and Vibration Control, Center for Noise and Vibration, Korea.
Nguyen, T., Kwok, N., Ha, Q.P., Li, J. & Samali, B. 2006, 'Adaptive sliding mode control for civil structure using magnetorheological dampers', Proceedings 23rd International Symposium on Automation and Robotics in Construction, Japan Robot Association, Tokyo, Japan, pp. 636-641.
Choi, F., Samali, B., Crews, K.I. & Li, J. 2006, 'Calibration of a Laboratory Timber Bridge Finite Element Model using the Experimental Modal Data', Proceedings CD of WCTE 2006 - 9th World Conference on Timber Engineering, WCTE 2006, USA, pp. 1-8.
In recent years, a great deal of attention has been focused on the condition and safety of aging timber bridges in Australia. Vibration-based damage identification techniques to detect structural deterioration at an early stage have significant potential to reduce the costs and down-time associated with repair of damaged members as well as enhancing the safety and reliability of timber bridges. In this paper, the process of developing and calibrating a scale timber bridge, which accurately simulates the behaviour of a ?real? bridge under laboratory conditions, is presented. A finite element (FE) model has been developed and calibrated with experimental modal data. The FE model shows acceptable correlations when compared to the experimental data, with minor adjustment of the actual material properties. It forms a tool for predicting the behaviour of the damaged laboratory bridge, as well as potential identification of damage in real timber bridges.
Kwok, N., Ha, Q.P., Li, J. & Samali, B. 2005, 'Parameter Identification for a Magnetorheological Fluid Damper: An Evolutionary Computation Approach', Proceedings of the 6th International Symposium on Intelligent Technologies, Faculty of Science and Technology, Assumption University, Bangkok, Thailand, pp. 115-122.
Dowling, D.M., Price, H.V. & Samali, B. 2005, 'Shear Strength of Adobe-Mudbrick Mortar Joints', Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, Tour Hosts Pty Limited, Australia, pp. 1-10.
Wu, H. & Samali, B. 2005, 'Control of Building Vibration Against Earthquakes', Proceedings of ACOUSTICS 2005, Australian Acoustic Society, Victoria, Australia, pp. 189-193.
An aseismic hybrid control system was employed to protect a five-storey benchmark-building model against strong earthquakes. The hybrid control system consists of a base isolation system (laminated rubber bearings) connected to an active control system (a tuned mass damper and an actuator). A five-storey benchmark model is developed to study the effectiveness of the hybrid control system against different ground motions: El-Centro 1940, Hachinohe 1968, Kobe 1995, and Northridge 1994 earthquakes. It was found from the numerical results, that the rubber bearing system alone can perform well against Hachinohe and Northridge ground motions, but not well enough to protect the lower floors of the model against El-Centro and Kobe ground motions. After an active control system was implemented to the rubber-isolated model, further improvements in earthquake resistance against these four earthquakes were obtained, especially against the El-Centro and Kobe. It is shown that a combined use of active and passive control systems, (referred to as hybrid control system), is more effective in reducing the building response under strong earthquakes.
Samali, B., Dowling, D.M. & Li, J. 2005, 'Dynamic Testing of Unreinforced U-Shaped Adobe-Mudbrick Wall Unit', Developments in Mechanics of Structures and Materials, A A Balkema, London, United Kingdom, pp. 505-510.
Samali, B., Widjaja, J.H., Li, J. & Reizes, J. 2005, 'Smart Braced Frame Systems', Developments in Mechanics of Structures and Materials, A. A. Balkema, London, United Kingdom, pp. 401-406.
Samali, B., Widjaja, J.H., Li, J., Dackermann, U. & Brown, P.W. 2005, 'Amplitude Frequency Characteristics of 'Smart'-Pin Frame System', Proceedings of the 11th Asia Pacific Vibration Conference, Universiti Teknologi Malaysia, Langkawi, Malaysia, pp. 228-233.
Samali, B., Dowling, D.M. & Li, J. 2005, 'Dynamic Response of U-Shaped Adobe-Mudbrick Wall Units', Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, Tour Hosts Pty Limited, Australia, pp. 1-9.
Widjaja, J.H., Samali, B., Li, J. & Reizes, J. 2005, 'Seismic Structural Control Investigations Using a Prototype Magnetorheological Shear Damper', Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, Tour Hosts Pty Limited, Australia, pp. 1-11.
Widjaja, J.H., Samali, B., Li, J. & Reizes, J. 2005, 'Dynamic Frequency De-Tuning Using Controllable Beam-Column Semi-Rigid Connections', Proceedings of 4th Australasian Congress on Applied Mechanics, Institute of Materials Engineering Australasia Ltd, North Melbourne, Australia, pp. 807-813.
Choi, F., Samali, B., Li, J., Brown, P.W. & Dackermann, U. 2005, 'Investigation on the Dynamic Response of a Damaged Bridge', Proceedings of the 11th Asia-Pacific Vibration Conference, Universiti Teknologi Malaysia, Langkawi, Malaysia, pp. 274-280.
Choi, F., Samali, B., Crews, K.I. & Li, J. 2005, 'Static and Dynamic Evaluation of Continuity Effect of Corbels in Timber Bridges', Proceedings of 4th Australasian Congress on Applied Mechanics, Institute of Materials Engineering Australasia Ltd, North Melbourne, Australia, pp. 285-292.
Choi, F., Samali, B. & Crews, K.I. 2005, 'Pilot Investigation of Continuity Effect of Corbel in Timber Bridges', Developments in Mechanics of Structures and Materials, A A Balkema Publishers, Great Britain, pp. 1311-1316.
Dowling, D.M., Samali, B. & Li, J. 2005, 'An Improved Means of Reinforcing Adobe Walls-External Vertical Reinforcement', Sismo Adobe 2005, Pontificia Universidad Catolica del Peru, Lima, Peru, p. CD Rom.
Li, J. & Samali, B. 2005, 'Fuzzy Sliding Mode Control of Seismically Excited Structure Using Magnetorheological Dampers', Developments in Mechanics of Structures and Materials, A A Balkema, London, United Kingdom, pp. 479-484.
Li, J., Samali, B., Choi, F. & Dackermann, U. 2005, 'Damage Identification of Timber Bridge Using Vibration Based Methods', Proceedings of the 11th Asia-Pacific Vibration Conference, Universiti Teknologi Malaysia, Langkawi, Malaysia, pp. 662-668.
Li, J., Samali, B., Crews, K.I. & Shestha, R. 2005, 'Theoretical and Experimental Studies on Assessment of Bridges Using Simple Dynamic Procedures', Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, Tour Hosts Pty Limited, Australia, pp. 1-11.
Li, J., Samali, B. & Smith, S.T. 2005, 'Stiffness estimation and damage detection of fibre reinforced polymer strengthened reinforced concrete beams using a vibration-based method', 4th Australasian Congress on Applied Mechanics, ACAM 2005, pp. 663-669.
Reinforced concrete (RC) structural elements can be strengthened by bonding high-strength, noncorrosive fibre reinforced polymer (FRP) composites to their surfaces. In the majority of strengthening situations the existing structure would have been subjected to extreme loading at some stage of its life. It is of great interest to designers and users of structures to be aware of the condition of the structural elements, particularly with regards to damage, prior to the design and application of FRP strengthening measures. This paper reports the results of a vibration-based method for assessing damage in RC beams prior to and after the application of FRP strengthening. The vibration-based method measures the vibrations of beams with and without additional mass and provides an assessment of the degree of damage as well as stiffness of the structural element. A simply supported RC beam was constructed and initially damaged by loading to 50% of its flexural capacity. FRP strengthening was then applied and the beam tested to failure. Vibration measurements were taken prior to and after damage of the plain beam as well as after application of the FRP strengthening. The proposed method was used for detecting damage and evaluating the repair as well as quantitatively estimating in-service stiffness of the beams. Good correlation between dynamic results and static load test results is found, thus demonstrating the potential of the vibration-based method. Institute of Materials Engineering Australasia Ltd 2005.
Crews, K.I., Samali, B. & Al-Dawod, M. 2005, 'Reliable Assessment of Road Bridges Using Dynamic Procedures', Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, Tour Hosts Pty Ltd, Australia, pp. 1-10.
Boffa, J., Zhang, N. & Samali, B. 2005, 'Study on Model Reduction of Large Structural Systems for Active Vibration Control', Proceedings of 4th Australasian Congress on Applied Mechanics, The Institute of Materials Engineering, Australasia Ltd, Melbourne, Australia, pp. 293-298.
Kwok, N., Nguyen, T., Ha, Q.P., Li, J. & Samali, B. 2005, 'MR Damper Structural Control Using a Multi-Level Sliding Mode Controller', Australian Earthquake Engineering Society Proceedings of the 2005 Conference, Australian Earthquake Engineering Society, Victoria, Australia, pp. 1-7.
Li, J. & Samali, B. 2005, 'Recent studies on structural control of five storey benchmark model', 4th International Workshop for Structural Control, DEStech Publications, Inc, United States of America, pp. 110-115.
As one of the benchmark models encouraged by the International Association for Structural Control (IASC), a five story experimental benchmark building model was designed and fabricated by the University of Technology Sydney in 1999. In the past four years, a number of structural control studies have been carried out on the benchmark model including passive, active and semi-actice controls. In this paper, the benchmark model is presented and a review is given on the benchmark model related research, especially the experimental studies.
Ha, Q.P., Wu, Y., Samali, B. & Li, J. 2004, 'Earthquake Response of a Building Model with Base-Isolated Active Control', Preprints of the 3rd IFAC Symposium on Mechatronics Systems, Casual Productions, Glenelg North, SA, Sydney, Australia, pp. 687-692.
Place published ?- CD ROM
Crews, K.I., Samali, B., Bakoss, S.L. & Champion, C. 2004, 'Testing and Assessment Procedures to Facilitate the Management of Timber Bridges Assets', The 3rd Civil Engineering Conference in the Asian Region Proceedings, Asian Civil Engineering Coordination Council, Seoul, Korea, pp. 229-234.
Crews, K.I., Samali, B., Bakoss, S.L. & Champion, C. 2004, 'Overview of Assessing Load Carrying Capacity of Timber Bridges Using Dynamic Methods', Proceedings of the Austroads 2004 Bridge Conference, Austroads Incorporated, Sydney, Australia, pp. 1-12.
Dowling, D.M., Samali, B. & Li, J. 2004, 'Shake Table Testing of Unreinforced and Highly Reinforced U-shape Adobe-Mudbrick Wall Units', Australian Earthquake Engineering in the New Millenium, Australian Earthquake Engineering Society, Victoria, Australia, pp. 1-6.
Dowling, D.M., Diaz, J. & Samali, B. 2004, 'Horizontal Shear Testing of Mudbrick Masonry Mortar Joints', Proceedings of the 7th Australasian Masonry Conference, The University of Newcastle, NSW, Newcastle, Australia, pp. 378-387.
Crews, K.I., Samali, B. & Li, J. 2004, 'Reliable assessment of aged timber bridges using dynamic procedures', Proceedings of the 8th World Conferences on Timber Engineering, WCTE 2004, WCTE, Finland, pp. 1001-1006.
Since late 2001, a new assessment method has been developed by the authors that incorporates two significant innovations enabling reliable prediction of the strength of the old timber bridges. The first innovation is the use of a dynamic based testing method that accurately determines the global stiffness of a bridge deck, whilst reducing both the time required and cost of testing to about 20% of that for traditional static load tests. The dynamic testing procedure involves the attachment of accelerometers underneath the bridge girders, which are then excited by a modal hammer. The method analyses the dynamic responses with and without extra mass, so that the overall flexural stiffness of the bridge can be obtained. Recent refinements by the authors have also enabled determination of the individual member stiffness and identification of defective members in the bridge structure. The second innovation involves the development of a reliability based strength model, which has been derived from analysis of extensive test data using a probabilistic relationship between the measured girder stiffness and the bending moment capacity of the timber girders. This paper describes research and development of the method and discusses its application in successfully undertaking testing of some 100 old? timber bridges in Australia.
Samali, B., Widjaja, J.H., Li, J. & Reizes, J. 2003, 'Magneto-rheological Shear Dampers; Quasi-static Modelling and Simulation', Proceedings of the 10th Asia Pacific Vibration Conference, Queensland University of Technology, Brisbane, Australia, pp. 1-6.
Samali, B., Djajakesukma, S., Nguyen, H.T. & Li, J. 2003, 'An Experimental Study of a Five Storey Steel Frame Using Semi-active Control System', Proceedings of the 10th Asia Pacific Vibration Conference, Queensland University of Technology, Brisbane, Australia, pp. 604-609.
Mayol, E., Samali, B., Kwok, K.C. & Li, J. 2003, 'Vibration Control of An Experimental Benchmark Model To Earthquake Using Liquid Column Vibration Absorbers (LCVAs)', Proceedings of the 10th Asia Pacific Vibration Conference, Queensland University of Technology, Brisbane, Australia, pp. 451-456.
Wu, Y., Samali, B. & Li, J. 2003, 'Seismic Response of Torsionally Sensitive Building Models', Proceedings of the 10th Asia Pacific Vibration Conference, Queensland University of Technology, Brisbane, Australia, pp. 765-770.
Li, J., Samali, B. & Crews, K.I. 2003, 'Determining Individual Member Stiffness of Bridge Structure Using a Simple Dynamic Procedure', Proceedings of the 10th Asia Pacific Vibration Conference, Queensland University of Technology, Gold Coast, Queensland, Australia, pp. 379-384.
Crews, K.I., Samali, B., Li, J. & Bakoss, S.L. 2003, 'Assessing the Load Capacity of Timber Bridges Using Dynamic Methods', Proceedings of the NSW IPWEA State Conference 2002 - Coffs Harbour, IPWEA, Australia, pp. 1-10.
Samali, B., Bakoss, S.L., Li, J., Saleh, A. & Wije, A. 2003, 'Assessing the Structural Adequacy of a 3-span Steel-Concrete Bridge Using Dynamic Methods: A case study', Abstracts of the Tenth International Conference: Structural Faults & Repair Abstracts, ENGINEERING TECHNICS PRESS, UK.
Djajakesukma, S., Samali, B. & Nguyen, H.T. 2002, 'Vibration control of five storey model with semi-active stiffness damper', Applied Mechanics: Progress and Applications, World Scientific, Sydney, Australia, pp. 653-658.
Dowling, D.M. & Samali, B. 2002, 'Improved seismic resistance of mudbrick building', Advances in Mechanics of Structures and Materials, A.A. Balkema Publishers, Lisse, Netherlands, pp. 657-662.
Li, J., Samali, B. & Chapman, C. 2002, 'Experimental realisation of active control of a five storey building model using SMA actuators', Advances in Mechanics of Structures and Materials, A.A. Balkema Publishers, Australia, pp. 699-704.
Mayol, E., Samali, B., Kwok, K.C., Wood, G.S., Mack, A.N. & Hitchcock, P. 2002, 'Damping enhancement of liquid column vibration absorbers for structural control', Advances in Mechanics of Structures and Materials, A.A. Balkema Publishers, Lisse, Netherlands, pp. 715-720.
Pokharel, A.P., Samali, B. & Perera, N.J. 2002, 'Dynamic facades fro buildings', Advances in Mechanics of Structures and Materials, A.A. Balkema Publishers, Australia, pp. 745-750.
Samali, B., Djajakesukma, S. & Nguyen, H.T. 2002, 'Robustness of semi-active stiffness damper with system uncertainty', Advances in Mechanics of Structures and Materials, A.A. Balkema Publishers, Australia, pp. 763-768.
Samali, B., Mayol, E., Mack, A.N., Kwok, K.C. & Hitchcock, P. 2002, 'Vibration control of a five storey benchmark building excited by earthquake using liquid column vibrator absorbers', Applied Mechanics Progress and Applications, World Scientific, Singapore, pp. 641-646.
Samali, B., Wu, Y. & Li, J. 2002, 'Torsional response of a base-isolated eccentric building model', Advances in Mechanics of Structures and Materials, A.A. Balkema Publishers, Australia, pp. 769-774.
Wu, Y., Samali, B. & Li, J. 2002, 'Earthquake resistance performance of laminated and lead core rubber bearings', Applied Mechanics Progress and Applications, World Scientific, Singapore, pp. 659-664.
Li, J., Samali, B. & Ha, Q.P. 2002, 'Fuzzy sliding mode control of a five storey benchmark model equipped with active mass driver (AMD)', Proc. the Int. Conference on Motion Control and Vibration (MOVIC'02), Proc. the Int. Conference on Motion Control and Vibration (MOVIC02), Saitama Japan, pp. 172-177.
Li, J., Samali, B. & Chapman, C. 2002, 'Variable structure control of seismically excited structure with shape memory alloy actuators', Applied Mechanics Progress and Applications, World Scientific, Australia, pp. 665-670.
Samali, B., Al-Dawod, M. & Li, J. 2002, 'Performance of a five storey benchmark model using an active mass driver and a fuzzy controller', Proceedings of the Third Australasian Congress on Applied Mechanics, World Scientific Publishing, Singapore, pp. 647-652.
Li, J., Djajakesukma, S., Samali, B. & Nguyen, H.T. 2002, 'Modeling and Identificaion of MR Damper for Semi-Active Control Devices', The 6th International Conference on Motion and Vibration Control MOVIC 2002, MOVIC, Japan.
Samali, B., Al-Dawod, M. & Li, J. 2002, 'Performance of An Active Mass Driver System on A Five Storey Benchmark Model', The 6th International Conference on Motion and Vibration Control, MOVIC 2002, MOVIC, Japan.
Benitez, M., Bakoss, S.L., Crews, K.I. & Samali, B. 2001, 'To develop new cost effective procedures for testing the structural response of short/medium span bridge decks', Proceedings of IABSE Conference Lahti 2001 - Innovative woodened structures and Bridges, International Association for Bridge and Structural Engineering, Lahti, Finland, pp. 257-262.
Ha, Q.P., Li, J., Hong, G. & Samali, B. 2001, 'Active structural control using dymanic output feedback sliding mode', Proceedings of the Australian Conference on Robotics and Automation ACRA'01, Australian Robotics & Automation Association, Sydney, pp. 20-25.
Samali, B., Djajakesukma, S. & Nguyen, H.T. 2001, 'Effectiveness of semi-active stiffness damper in five-storey model', Proceedings of Computational Mechanics, Elservier Science Ltd., Australia, pp. 1425-1430.
Samali, B. & Wu, Y. 2001, 'Hybrid control of a five-storey benchmark model subjected to strong eartthquakes', Proceedings of Computational Mechanics, Elservier Science Ltd., Australia, pp. 1437-1442.
Samali, B., Mayol, E., Kwok, K.C., Mack, A.N. & Hitchcock, P. 2001, 'Vibration control of a 5-storey benchmark building utilising liquid column vibration absorbers', Proceedings of Computational Mechanics, Elservier Science Ltd., Australia, pp. 1431-1436.
Samali, B., Djajakesukma, S. & Nguyen, H.T. 2001, 'A four-node hybrids stress finite element with penalized functions', Proceedings of Computational Mechanics, Elservier Science Ltd., Australia, pp. 1697-1702.
Al-Dawod, M., Samali, B., Kwok, K.C. & Wong, Y. 2001, 'Application of a fuzzy controller to seismically excited nonliner buildings', Proceedings of The 10th IEEE International Conferene on Fuzzy Systems, The Institute of Electrical and Electronic Engineers, Inc., Australia, pp. 0-0.
Samali, B. & Madadnia, J. 2001, 'Wind Simulation In An Environmental Wind Tunnel For Both Structure And Performance Studies', Proceedings of Twelfth International Association of Hydraulic Research (12thIAHR) Symposium on Cooling Towers and Heat Exchangers, University of Technology Sydney (UTS), University of Technology Sydney (UTS), pp. 44-52.
This paper describes methods used to develop a scaled model of wind flows in a atmospheric boundary layer wind tunnel for both structural effects and assessment of wind-induced performance losses. Boundary layer wind tunnel was used to simulate wind flows for cooling tower studies on a 1/250 scaled model of a 250 MWe prototype natural draft cooling tower. The tests were concentrated on flow effects around the inlet region, as this area is most relevant for retrofitting of performance enhancing structures. Various flow- conditioning devices were used to develop the desired turbulent profile. Suitability of simulated wind velocity and turbulence intensity profiles for cooling tower performance studies is discussed.
Li, J. & Samali, B. 2001, 'Comparison of Different Control Algorithms For SMA Actuators', 8th East Asia-Pacific Conference on Structural Engineering and Construction, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore, Singapore.
Li, J. & Samali, B. 2001, 'Sliding Mode Control Of Five Storey Benchmark Model With Magnetorheological (MR) Damper', Eighth East Asia-Pacific Conference on Structural Engineering and Construction, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore, Singapore.
Wu, Y., Samali, B., Li, J. & Mayol, E. 2001, 'Experimental Modal Analysis of a Five Storey Benchmark Model', The 19th International Modal Analysis Conference, Society for Experimental Mechanics, Inc., USA.
Samali, B., Djajakesukma, S. & Nguyen, H.T. 2000, 'A Comparison of Control Laws for a Semi-Active Stiffness Damper', Proceedings of the 5th International Conference on Motion and Vibration Control '2000, UTS, Sydney, pp. 737-742.
Samali, B., Al-Dawod, M., Nguyen, H.T. & Murphy, G. 2000, 'Design and Performance Verification of an Active Mass Damper', Proceedings of the 5th International Conference on Motion and Vibration Control '2000, UTS, Sydney, pp. 837-842.
Wu, H., Samali, B. & Nguyen, H.T. 2000, 'Shake Table Tests on the Seismic Response of a Five Storey Benchmark Model Isolated with Rubber Bearing', Proceedings of the 5th International Conference on Motion and Vibration Control '2000, UTS, Sydney, pp. 353-358.
Samali, B., Wu, H. & Nguyen, H.T. 2000, 'Analytical Study of the Seismic Response of a Base Isolated Five-Storey Benchmark Model', Proceedings of the 5th International Conference on Motion and Vibration Control '2000, UTS, Sydney, pp. 463-468.
Djajakesukma, S., Samali, B. & Nguyen, H.T. 2000, 'Application of a Semi Active Stiffness Damper to a Five Storey Benchmark Model', Proceedings of the 5th International Conference on Motion and Vibration Control '2000, UTS, Sydney, pp. 569-574.
Li, J. & Samali, B. 2000, 'Control of a Five Storey Building Model Under Benchmark Earthquake Using SMA Actuators', The 5th International Conference on Motion and Vibration Control, Centre for Built Infrastructure Research, University of Technology, Sydney, Australia.
Wu, Y., Samali, B., Li, J. & Bakoss, S.L. 2000, 'Shock Test and Stress Analysis of a Heavy Metal Forge', The 7th International Symposium of Structural Failure and Plasticity, Pergamon an imprint of Elsevier Science, Amsterdam.
Li, J., Samali, B. & Wu, Y. 1999, 'Qualification Testing of Network Cabinets Using a Shake', The 10th Anniversary of the Newcastle Earthquake, Australian Earthquake Engineering Society, Sydney, Australia, p. 11.
Wu, Y., Samali, B., Li, J. & Nguyen, H.T. 1999, 'Modal Analysis of XBJ2 Automobile', International Conference on Application of Modal Analysis '99, The University of Queensland, Brisbane, Australia.
Li, J., Samali, B. & Wu, Y. 1999, 'Improving Seismic Behaviour of Network System Enclosures Using Modal Analysis', The International Conference of Applications of Modal Analysis '99, The University of Queensland, Brisbane, Australia.
Samali, B., Li, J., Mayol, E. & Wu, Y. 1999, 'System Identification of a Five Storey Benchmark Model Using Exprimental Modal Analysis', The International Conference on Application of Modal Analysis '99, The University of Queensland, Brisbane, Queensland, Australia.
Al-Dawod, M., Naghdy, F., Samali, B. & Kwok, K.C. 1999, 'Active Control of Wind Excited Structures Using Fumy Logic', Fuzzy Systems Conference Proceedings, 1999. FUZZ-IEEE '99. 1999 IEEE International, IEEE, Seoul, Korea, pp. 72-77.
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The first stage in the development of a fuzzy controller for active control of vibration in a wind excited tall structure is reported. The initial rule base of the fuzzy controller is developed based on the input/output data obtained from the performance of the system under a state feedback controller. The performance of the developed controller is validated through computer simulation. The controller is applied to both the building model from which the rule base is extracted and another building with similar dynamics but different parameters. The developed controller has significantly outperformed a state feedback controller and a previously developed intuitive fuzzy controller in terms of the maximum required control force. The amplitude of the steady state oscillation produced by the state feedback controller has, however, proved to be marginally better than the other two controllers
Bakoss, S.L., Samali, B. & Li, J. 1997, 'A Facility for Dynamic Testing and Research', The 1997 Conference of the Australian Earthquake Engineering Society, Australian Earthquake Engineering Society, Australia.
Samali, B. & Forrest-Brown, G. 1989, 'Active Control Systems for Wind-Sensitive Structures', Institution of Engineers, Australia. National Conference, Institution of Engineers, Australia, ACT, Australia, pp. 237-246.
The effectiveness of active mass dampers in reducing the wind-induced structural response of tall buildings has been shown. The active mass damper methodology has the potential to provide significant increases in height or building flexibility with the addition of minor penalties to form or cost. The system can demonstrably provide a substantial reduction in additional stiffness and mass requirements for the serviceability limit state. A significant benefit will be an increase in the utilisation of sites by reducing the "footpad" of tall buildings, or conversely by the improved use of sites at ground level for the same reason. Planning advantages accruing from the system will include reduced conflicts between structure and services in the building enclosure due to reduced bulk in the frame members, and better use of lettable spaces and reduced planning penalties in tall buildings.
Samali, B. 1987, 'Active Control of Tall Buildings under Environmental Loads', First National Structural Engineering Conference 1987, Institution of Engineers, Australia, Barton, ACT, Australia, pp. 93-98.
An investigation is made of the possible application of an active mass damper control system to tall buildings excited by strong wind turbulence and ground motion. The effectiveness of active control system, as measured by the reduction of the coupled lateral-torsional motions of tall buildings is studied. The wind turbulence is modeled as a stochastic process that is stationary in time but non-homogeneous in space. The earthquake ground acceleration is modeled as a uniformly modulated non-stationary random process. The problem is formulated using the transfer matrices approach, and a closed-loop control law. The random vibration analysis is carried out to determine the statistics of the building responses, the required active control forces, and mass damper displacements. The method of Monte-Carlo simulation is also employed to demonstrate the building response behaviour with or without an active control system. A numerical example of a forty-storey building under strong wind and earthquake excitations is given to illustrate the significant reduction of the building acceleration response by use of an active mass damper control system.

Journal articles

Sadeghi Hokmabadi, A., Fatahi, B. & Samali, B. 2014, 'Assessment of soil-pile-structure interaction influencing seismic response of mid-rise buildings sitting on floating pile foundations', Computers and Geotechnics, vol. 55, no. 1, pp. 172-186.
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The role of the seismic soilpilestructure interaction (SSPSI) is usually considered beneficial to the structural system under seismic loading since it lengthens the lateral fundamental period and leads to higher damping of the system in comparison with the fixed-base assumption. Lessons learned from recent earthquakes show that fixed-base assumption could be misleading, and neglecting the influence of SSPSI could lead to unsafe design particularly for structures founded on soft soils. In this study, in order to better understand the SSPSI phenomena, a series of shaking table tests have been conducted for three different cases, namely: (i) fixed-base structure representing the situation excluding the soilstructure interaction; (ii) structure supported by shallow foundation on soft soil; and (iii) structure supported by floating (frictional) pile foundation in soft soil. A laminar soil container has been designed and constructed to simulate the free field soil response by minimising boundary effects during shaking table tests. In addition, a fully nonlinear three dimensional numerical model employing FLAC3D has been adopted to perform time-history analysis on the mentioned three cases. The numerical model adopts hysteretic damping algorithm representing the variation of the shear modulus and damping ratio of the soil with the cyclic shear strain capturing the energy absorbing characteristics of the soil. Results are presented in terms of the structural response parameters most significant for the damage such as foundation rocking, base shear, floor deformation, and inter-storey drifts. Comparison of the numerical predictions and the experimental data shows a good agreement confirming the reliability of the numerical model. Both experimental and numerical results indicate that soilstructure interaction amplifies the lateral deflections and inter-storey drifts of the structures supported by floating pile foundations in comparison to the fixed base structures. However, the floating pile foundations contribute to the reduction in the lateral displacements in comparison to the shallow foundation case, due to the reduced rocking components.
Fatahi, B., Tabatabaiefar, S. & Samali, B. 2014, 'Soil-structure interaction vs Site effect for seismic design of tall buildings on soft soil', Geomechanics and Engineering: An International Journal, vol. 6, no. 3, pp. 293-320.
In this study, in order to evaluate adequacy of considering local site effect, excluding soil-structure interaction (SSI) effects in inelastic dynamic analysis and design of mid-rise moment resisting building frames, three structural models including 5, 10, and 15 storey buildings are simulated in conjunction with two soil types with the shear wave velocities less than 600 m/s, representing soil classes De and Ee according to the classification of AS1170.4-2007 (Earthquake actions in Australia) having 30 m bedrock depth. Structural sections of the selected frames were designed according to AS3600:2009 (Australian Standard for Concrete Structures) after undertaking inelastic dynamic analysis under the influence of four different earthquake ground motions. Then the above mentioned frames were analysed under three different boundary conditions: (i) fixed base under direct influence of earthquake records; (ii) fixed base considering local site effect modifying the earthquake record only; and (iii) flexible-base (considering full soil-structure interaction). The results of the analyses in terms of base shears and structural drifts for the above mentioned boundary conditions are compared and discussed. It is concluded that the conventional inelastic design procedure by only including the local site effect excluding SSI cannot adequately guarantee the structural safety for mid-rise moment resisting buildings higher than 5 storeys resting on soft soil deposits.
Noushini, A., Vessalas, K. & Samali, B. 2014, 'Static Mechanical Properties of Polyvinyl Alcohol Fibre Reinforced Concrete (PVA-FRC)', Magazine Of Concrete Research, vol. 66, no. 1, pp. 1-19.
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This investigation assesses the performance of polyvinyl alcohol (PVA) fibres of two geometric lengths (6 and 12 mm) in concrete. Based on total concrete volume, 4 fibre fractions of 0.125%, 0.25%, 0.375% and 0.50% were evaluated for their effect on fresh and hardened properties of PVA fibre reinforced concretes (PVA-FRCs). Fly ash was also used as partial replacement of Portland cement in all mixes. By carrying out a comprehensive set of experiments, i. e., compressive strength, splitting tensile strength, modulus of elasticity, modulus of rupture and residual flexural strength, it was observed that PVA fibre significantly enhances the static mechanical properties of concrete as well as improving its post peak response and ductile behaviour.
Tabatabaiefar, S., Fatahi, B. & Samali, B. 2014, 'Numerical and Experimental Investigations on Seismic Response of Building Frames under Influence of Soil-Structure Interaction', Advances in Structural Engineering, An International Journal, vol. 17, no. 1, pp. 109-130.
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In this study, an enhanced numerical soil-structure model has been developed which treats the behaviour of soil and structure with equal rigour. The proposed numerical soil-structure model has been verified and validated by performing experimental shaking table tests. To achieve this goal, a series of experimental shaking table tests were performed on the physical fixed based (structure directly fixed on top of the shaking table) and flexible base (considering soil and structure) models under the influence of four scaled earthquake acceleration records and the results were measured. Comparing the experimental results with the numerical analysis predictions, it is noted that the numerical predictions and laboratory measurements are in a good agreement. Thus, the proposed numerical soil-structure model is a valid and qualified method of simulation with sufficient accuracy which can be employed for further numerical soil-structure interaction investigation studies. Based on the predicted and observed values of lateral deflections of fixed base and flexible base models, lateral deflections of the flexible base model have noticeably amplified in comparison to the fixed base model. As a result of the lateral deflection amplifications, it is observed that the performance level of the scaled structural model changed significantly which could be safety threatening.
Tabatabaiefar, S., Fatahi, B. & Samali, B. 2014, 'An empirical relationship to determine lateral seismic response of mid-rise building frames under influence of soil-structure interaction', The Structural Design of Tall and Special Buildings, vol. 23, no. 7, pp. 526-548.
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n this study, to determine the elastic and inelastic structural responses of mid-rise building frames under the influence of soilstructure interaction, three types of mid-rise moment-resisting building frames, including 5-storey, 10-storey and 15-storey buildings are selected. In addition, three soil types with the shear wave velocities less than 600m/s, representing soil classes Ce, De and Ee according to AS 1170.42007 (Earthquake action in Australia, Australian Standards), having three bedrock depths of 10m, 20m and 30m are adopted. The structural sections are designed after conducting nonlinear time history analysis, on the basis of both elastic method and inelastic procedure considering elastic-perfectly plastic behaviour ofstructural elements. The frame sections are modelled and analysed, employing finite difference method adopting FLAC2D software under two different boundary conditions: (a) fixed base (no soilstructure interaction) and (b) considering soilstructure interaction. Fully nonlinear dynamic analyses under the influence of different earthquake records are conducted, and the results in terms of the maximum lateral displacements and base shears for the above mentioned boundary conditions for both elastic and inelastic behaviours of the structural models are obtained, compared and discussed. With the results, a comprehensive empirical relationship is proposed to determine the lateral displacements of the mid-rise moment-resisting building frames under earthquake and the influence of soilstructure interaction.
Sadeghi Hokmabadi, A., Fatahi, B. & Samali, B. 2014, 'Seismic response of mid-rise buildings on shallow and end-bearing pile foundations in soft soil', Soils and Foundations, vol. 54, no. 3, pp. 345-363.
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The seismic behaviour of structures built on soft soil is influenced by the soil properties, and the response is significantly different from the fixed-base condition owing to the interaction between the ground and the structure. In this study, in order to investigate the influence of the foundation type on the response of structures, considering soilstructure interaction, a series of experimental shaking table tests has been conducted for three different cases, namely, (i) a fixed-base structure representing the situation excluding the soilstructure interaction; (ii) a structure supported by a shallow foundation on soft soil; and (iii) a structure supported by an end-bearing pile foundation in soft soil. A laminar soil container has been designed and constructed to simulate the free-field soil response by minimising the boundary effects. Simulating the superstructure as a multi-storey frame during the shaking table tests makes the experimental data unique. A fully nonlinear three-dimensional numerical model employing FLAC3D has been adopted to perform a time history analysis and to simulate the performance of the structure considering the seismic soilstructure interaction. Hysteretic damping of the soil is implemented to represent the variation in the shear modulus reduction factor and the damping ratio of the soil with cyclic shear strain. Free-field boundary conditions have been assigned to the numerical model and appropriate interface elements, capable of modelling sliding and separation between the pile and the soil elements, is considered. A comparison of the numerical predictions and the experimental data shows a good agreement confirming the reliability of the numerical model. Both experimental and numerical results indicate that soilstructure interaction amplifies the lateral deflections and inter-storey drifts of structures supported by end-bearing pile foundations in comparison to fixed-base structures. However, pile foundations contribute more to the reduction in lateral displacements than shallow foundations due to the reduced rocking components. Consequently, the choice of foundation type is dominant and should be included when investigating the influence of SSI on the response of superstructures during shaking excitations, which is significantly important in the performance-based design of structures.
Valipour Goudarzi, H., Vessali, N., Samali, B. & Foster, S. 2014, 'Reserve of strength in reinforced concrete frames: Analysis of arching action', Australian Journal of Structural Engineering, vol. 15, no. 2.
Nabavi, S., Nejadi, S. & Samali, B. 2014, 'Investigation in Mathematical Models of Chloride Diffusion Coefficient in Concrete Exposed to Marine Environment', Journal of Civil Engineering and Architecture, vol. 8, no. 4, pp. 456-463.
Degradation of reinforced concrete (RC) in maritime structures has become a worldwide problem due to its excessive costs of maintenance, repair, and replacement in addition to its environmental impacts and safety issues. Degradation of both concrete and steel which is the main reason of reduction in the service life of RC structures strongly depends on the diffusion process of moisture and aggressive species. In this paper, the major and popular mathematical models of diffusion process in concrete are surveyed and investigated. Predominantly in these models, the coefficient of chloride diffusion into the concrete is assumed to be constant. Whereas, experimental records indicate that diffusion coefficient is a function of time. Subsequently, data analysis and comparisons between the existing analytical models for predicting the diffusion coefficient with the existing experimental database are carried out in this study. Clearly, these comparisons reveal that there are gaps between the existing mathematical models and previously recorded experimental results. Perhaps, these gaps may be interpreted as influence of the other affecting parameters on the diffusion coefficient such as temperature, aggregate size and relative humidity in addition to the water cement ratio. Accordingly, the existing mathematical models are not adequate enough to predict the diffusion coefficient precisely and further studies need to be performed.
Vakiloroaya, V., Ha, Q.P. & Samali, B. 2013, 'Energy-efficient HVAC systems: Simulation-empirical modelling and gradient optimization', AUTOMATION IN CONSTRUCTION, vol. 31, pp. 176-185.
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Tabatabaiefar, S., Fatahi, B. & Samali, B. 2013, 'Lateral seismic response of building frames considering dynamic soil-structure interaction effects', Structural Engineering and Mechanics, vol. 45, no. 3, pp. 311-321.
In this study, to have a better judgment on the structural performance, the effects of dynamic Soil-Structure Interaction (SSI) on seismic behaviour and lateral structural response of mid-rise moment resisting building frames are studied using Finite Difference Method. Three types of mid-rise structures, including 5, 10, and 15 storey buildings are selected in conjunction with three soil types with the shear wave velocities less than 600m/s, representing soil classes Ce, De and Ee, according to Australian Standard AS 1170.4. The above mentioned frames have been analysed under two different boundary conditions: (i) fixed-base (no soil-structure interaction), and (ii) flexible-base (considering soil-structure interaction). The results of the analyses in terms of structural lateral displacements and drifts for the above mentioned boundary conditions have been compared and discussed. It is concluded that the dynamic soil-structure interaction plays a considerable role in seismic behaviour of mid-rise building frames including substantial increase in the lateral deflections and inter-storey drifts and changing the performance level of the structures from life safe to near collapse or total collapse. Thus, considering soil-structure interaction effects in the seismic design of mid-rise moment resisting building frames, particularly when resting on soft soil deposit, is essential.
Li, Y., Li, J., Li, W. & Samali, B. 2013, 'Development and characterization of a magnetorheological elastomer based adaptive seismic isolator', Smart Materials and Structures, vol. 22, no. 3.
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One of the main shortcomings in current base isolation design/practice is lack of adaptability. As a result, a base isolation system that is effective for one type earthquake may become ineffective or may have adverse effect for other earthquakes. The vulnerability of traditional base isolation systems can be exaggerated by two types of earthquakes, i.e. near-field earthquakes and far-field earthquakes. This paper addresses the challenge facing current base isolation design/practice by proposing a new type of seismic isolator for the base isolation system, namely an adaptive seismic isolator. The novel adaptive seismic isolator utilizes magnetorheological elastomer (MRE) for its field-sensitive material property. Traditional seismic isolator design with a unique laminated structure of steel and MRE layers has been adopted in the novel MRE seismic isolator. To evaluate and characterize the behavior of the MRE seismic isolator, experimental testing was conducted on a shake table facility under harmonic cycling loading. Experimental results show that the proposed adaptive seismic isolator can successfully alter the lateral stiffness and damping force in real time up to 37% and 45% respectively. Based on the successful development of the novel adaptive seismic isolator, a discussion is also extended to the impact and potential applications of such a device in structural control applications in civil engineering. 2013 IOP Publishing Ltd.
Aoki, Y., Valipour Goudarzi, H., Samali, B. & Saleh, A. 2013, 'A Study on Potential Progressive Collapse Responses of Cable-Stayed Bridges', Advances in Structural Engineering, An International Journal, vol. 16, no. 4, pp. 689-706.
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In this paper, a finite element (FE) model for a cable-stayed bridge designed according to Australian standards is developed and analysed statically and dynamically with and without geometrical nonlinearities. The dynamic amplification factor (DAF) and demand-to-capacity ratio (DCR) in different structural components including cables, towers and the deck are calculated and it is shown that DCR usually remains below one (no material nonlinearity occurs) in the scenarios studied for the bridge under investigation, however, DAF can take values larger than two. Moreover, effects of location, duration and number of cable(s) loss as well as effect of damping level on the progressive collapse resistance of the bridge are studied and importance of each factor on the potential progressive collapse response of the bridgeis investigated.
Vakiloroaya, V., Madadnia, J. & Samali, B. 2013, 'Modelling and performance prediction of an integrated central cooling plant for HVAC energy efficiency improvement', BUILDING SIMULATION, vol. 6, no. 2, pp. 127-138.
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Subhani, M., Li, J., Samali, B. & Yan, N. 2013, 'Determination of the embedded lengths of electricity timber poles utilizing flexural wave generated from impacts', Australian Journal of Structural Engineering, vol. 14, no. 1, pp. 85-96.
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Round timbers are extensively used as utility poles in Australia for electricity distribution and communication. Lack of information on their conditions results in great difficulties on asset management for industries. Despite the development of various non-destructive testing (NDT) techniques for evaluating the condition of piles, few NDTs are reported for applications on timber poles. This paper addresses challenges and issues on development of NDTs for condition assessment and embedded length of timber poles. For this paper, it is mainly focusing on determining the embedded length of the pole considering loss of the sufficient embedment length is a main factor compromising capacity and safety of timber poles. Since it is impractical for generating longitudinal waves by impacting from the top of poles, utilizing flexural wave from side impact on poles becomes attractive. However, the flexural wave is known by its highly dispersive nature. In this paper, one dimensional wave theory, guided wave theory and advanced signal processing techniques have been introduced in order to provide a solution for the problem. Two signal processing techniques, namely short kernel method and continuous wavelet transform, have been investigated for processing flexural wave signals to evaluate wave velocity and embedment length of timber poles in service. Institution of Engineers Australia, 2013.
Shrestha, R., Smith, S.T. & Samali, B. 2013, 'Finite element modelling of FRP-strengthened RC beam-column connections with ANSYS', COMPUTERS AND CONCRETE, vol. 11, no. 1, pp. 1-20.
Tabatabaiefar, S., Fatahi, B. & Samali, B. 2013, 'Seismic Behavior of Building Frames Considering Dynamic Soil-Structure Interaction', International Journal of Geomechanics, vol. 13, no. 4, pp. 409-420.
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The seismic excitation experienced by structures is a function of the earthquake source, travel path effects, local site effects, and soilstructure interaction (SSI) influences. The result of the first three of these factors is referred to as free-field ground motion. The structural response to free-field motion is influenced by the SSI. In particular, accelerations within structures are affected by the flexibility of the foundation support and variations between the foundation and free-field motions. Consequently, an accurate assessment of inertial forces and displacements in structures can require a rational treatment of SSI effects. In the current study, to depict these effects on the seismic response of moment-resisting building frames, a 10-story moment-resisting building frame resting on a shallow foundation was selected in conjunction with three soil types with shear-wave velocities of less than 600 m/s, representing Soil Classes Ce, De, and Ee according to an existing Australian Standard. The structural sections were designed after applying dynamic nonlinear time-history analysis, based on both the elastic method, and inelastic procedure using the elastic-perfectly plastic behavior of the structural elements. The frame sections were modeled and analyzed using the finite-difference method andthe FLAC 2D software under two different boundary conditions: (1) fixed-base (no SSI) and (2) considering the SSI. Fully nonlinear dynamic analysis under the influence of various earthquake records was conducted and the results of the two different cases for elastic and inelastic behavior of the structuralmodel were extracted, compared, and discussed. The results indicate that the performance level of themodel resting on Soil Class Ce does not change substantially and remains in the life safe level while the performance level of themodel resting on Soil Classes De and Ee substantially increase from the life safe level to near collapse for both elastic and inelastic cases. Thus, considering SSI effects in the elastic and inelastic seismic design of concrete moment-resisting building frames resting on Soil Classes De and Ee is essential. Generally, by decreasing the dynamic properties of the subsoil such as the shear-wave velocity and shear modulus, the base shear ratios decrease while interstory drifts of the moment-resisting building frames increase relatively. In brief, the conventional elastic and inelastic design procedure excluding the SSI is not adequate to guarantee structural safety for moment-resisting building frames resting on Soil Classes De and Ee.
Noushini, A., Samali, B. & Vessalas, K. 2013, 'Effect of polyvinyl alcohol (PVA) fibre on dynamic and material properties of fibre reinforced concrete', Construction And Building Materials, vol. 49, no. 1, pp. 374-383.
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The effect of uncoated polyvinyl alcohol (PVA) fibre addition on dynamic properties of fibre reinforced concrete (FRC) has been investigated in the current study. PVA fibres of two geometric lengths (6 and 12 mm) with aspect ratio of 428 and 857, respectively, were utilised. Fly ash was also used as partial replacement of Portland cement in all mixes. Based on total concrete volume, two fibre fractions of 0.25% and 0.5% were evaluated for their effect on fundamental frequency, dynamic modulus of elasticity and damping ratio of FRC. 28-Day static mechanical properties are also measured. From the results, it can be stated that although PVA fibre addition in low volume fractions used in this study significantly enhance the mechanical properties of FRC, it has no considerable effect on concrete material damping characteristics.
Li, Y., Li, J. & Samali, B. 2013, 'On the magnetic field and temperature monitoring of a solenoid coil for a novel magnetorheological elastomer base isolator', Journal of Physics: Conference Series, vol. 412, no. 1.
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Following a successful experimental validation of a magnetorheological elastomer (MRE) base isolator, this study presents one of the major concerns, the heating of the magnetic coil, in the design and development of the adaptive MRE based isolator. In this research, the MRE materials, with a total thickness of nearly 150 mm, are placed as the magnetic core of the device to best utilize the magnetic energy provided by the coil. A series of tests are undertaken to investigate the magnetic fields inside the coil with or without the MRE materials. Thermocouples are used to monitoring the surface temperature of the coil when it is applied with various currents for 10 min. It is shown that the measurement of field inside the solenoid when no MRE is placed inside agrees with the theoretical analysis. It is also shown that the temperature of the coil increase dramatically when a current is applied. Cooling of the coil may takes even longer, about 4 h, till down to the room temperature. Dropping of the magnetic field is observed when the temperature goes high. Published under licence by IOP Publishing Ltd.
Zheng, L., He, S., Samali, B. & Yang, L.T. 2013, 'An Algorithm for Accuracy Enhancement of License Plate Recognition', Journal of Computer and System Sciences, vol. 79, pp. 245-255.
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This paper presents an algorithm for extraction (detection) and recognition of license plates in traffic video datasets. For license plate detection, we introduce a method that applies both global edge features and local Haar-like features to construct a cascaded classifier consisting of 6 layers with 160 features. The characters on a license plate image are extracted by a method based on an improved blob detection algorithm for removal of unwanted areas. For license plate recognition (i.e., character recognition), an open source OCR is modified and used. Our proposed system is robust under poor illumination conditions and for moving vehicles. Our overall system is efficient and can be applied in real-time applications. Experimental results are demonstrated using a traffic video
Dackermann, U., Li, J. & Samali, B. 2013, 'Identification of member connectivity and mass changes on a two-storey framed structure using frequency response functions and artificial neural networks', Journal of Sound and Vibration, vol. 332, no. 16, pp. 3636-3653.
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This paper presents a structural health monitoring (SHM) technique that utilises pattern changes in frequency response functions (FRFs) as input parameters for a system of artificial neural networks (ANNs) to assess the structural condition of a structure. To verify the proposed method, it is applied to numerical and experimental models of a two-storey framed structure, on which structural damage is induced by member connectivity and mass changes, respectively. For the numerical structure, simulated time-history data are polluted with various levels of white Gaussian noise in order to realistically represent field-testing conditions. As a damage indicator, residual FRFs are used, which are derived by calculating the differences in FRF data between the undamaged/baseline structure and the structure with changed joint conditions or added mass. To obtain suitable patterns for neural network training, principal component analysis (PCA) techniques are adopted to reduce the size of the residual FRF data and to filter noise. A hierarchical system of individual ANNs, termed network ensemble, is then trained to map changes in PCA-reduced residual FRFs to damage conditions. The results obtained for both damage investigations, namely joint damage and mass changes, demonstrate that the proposed SHM technique is accurate and reliable in assessing the condition of the test structure numerically and experimentally based on direct FRF measurements and network ensemble analysis. From the outcomes of the individual networks, it is found that the proposed hierarchical network ensemble approach is highly efficient in filtering poor results of underperforming networks obtained from measurement locations with low damage sensitivity. 2013 Elsevier Ltd.
Vessali, N., Valipour Goudarzi, H., Samali, B. & Foster, S. 2013, 'Development of arching action in longitudinally-restrained reinforced concrete beams', Construction And Building Materials, vol. 47, no. 1, pp. 7-19.
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Membrane action of reinforced concrete (RC) beams is one of the primary mechanisms that enhances progressive collapse resistance of frames and influences the robustness of a structure under an unforeseen overload event. Compressive membrane action increa
Liu, J., Ding, G.K. & Samali, B. 2013, 'Building sustainable score (BSS) - A hybrid process approach for sustainable building assessment in China', Journal of Power and Energy Engineering, vol. 1, no. 5, pp. 58-62.
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Sustainable building in China has gained attention both domestically and abroad. Despite the fast increase in sustainable assessment tools developed locally or adopted from overseas, there are still criticisms about the current situation of weak implementation and lack of comprehensive consideration. The lack of consideration of economic and social as-pects or building performance on whole building life cycle all lead to departure from the true meaning of sustainable development. And lack of participation on the part of stakeholders makes it too theoretical to be carried out. This re-search aims to develop a model to address this problem. This research started with review of current sustainable as-sessment tools applied in China. As the assessment indicators have clear regional disparities, and almost no current tool considers all three pillars of environmental, economic and social in building life cycle. An industry survey was therefore designed for generation of indicators at different building stages, and personal interviews relevant to different occupa-tion in building industry were conducted to complement the questionnaire survey. After that, the model Building Sus-tainable Score (BSS) was developed based on the stakeholders participation. Finally, the model is verified by a case study.
Aslani, F. & Samali, B. 2013, 'Predicting the bond between concrete and reinforcing steel at elevated temperatures', Structural Engineering And Mechanics, vol. 48, no. 5, pp. 643-660.
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Reinforced concrete structures are vulnerable to high temperature conditions such as those during a fire. At elevated temperatures, the mechanical properties of concrete and reinforcing steel as well as the bond between steel rebar and concrete may signi
Askari, M., Li, J. & Samali, B. 2013, 'A multi-objective subtractive FCM based TSK fuzzy system with input selection, and its application to dynamic inverse modelling of MR dampers', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), vol. 7894 LNAI, no. PART 1, pp. 215-226.
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A new encoding scheme is presented for a fuzzy-based nonlinear system identification methodology, using the subtractive Fuzzy C-Mean clustering and a modified version of non-dominated sorting genetic algorithm. This method is able to automatically select the best inputs as well as the structure of the fuzzy model such as rules and membership functions. Moreover, three objective functions are considered to satisfy both accuracy and compactness of the model. The proposed method is then employed to identify the inverse model of a highly nonlinear structural control device, namely Magnetorheological (MR) damper. It is shown that the developed evolving Takagi-Sugeno-Kang (TSK) fuzzy model can identify and grasp the nonlinear dynamics of inverse systems very well, while a small number of inputs and fuzzy rules are required for this purpose. 2013 Springer-Verlag.
Vakiloroaya, V., Fakhar, A., Samali, B. & Pishghadam, K. 2013, 'Design improvement of central cooling plant for energy saving using cooling tower water', JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY, vol. 5, no. 5.
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Tabatabaiefar, S., Fatahi, B. & Samali, B. 2012, 'Finite Difference Modelling Of Soil-Structure Interaction For Seismic Design Of Moment Resisting Building Frames', Australian Geomechanics Journal, vol. 47, no. 3, pp. 113-119.
The importance of Soil-Structure Interaction (SSI) both for static and dynamic loads has been well established and the related literature spans at least 30 years of computational and analytical approaches for solving soil-structure interaction problems. Since the 1990s, great effort has been made to substitute the classical methods of design by new ones based on the concept of performance-based seismic design. Also, the necessity of estimating the vulnerability of existing structures and assessing reliable methods for their retrofit have greatly attracted the attention of engineering comunities in most seismic zones throughout the world. In the present study, in order to draw a clear picture of soil characteristics effects on seismic response of moment resisting building frames, a ten storey moment resisting building frame, resting on shallow foundation, is selected in conjunction with three soil types with shear wave velocities less than 600 m/s, representing soil classes Ce, De and Ee, according to Australian Standard AS 1170.4. The structure is modelled considering the three mentioned types of the soil deposits employing Finite Difference approach using FLAC 2D software. Fully nonlinear dynamic analyses under influence of different earthquake records are conducted, and the results of the different cases are compared and discussed. The results indicate that as shear wave velocity and shear modulus of the subsoil decrease, inter-storey drifts and subsequently the necessity of considering SSI effects in seismic design of moment resisting building frames increase. In general, by decreasing the subsoil stiffness, the effects of soil-structure interaction become more dominant and detrimental to the seismic behaviour of moment resisting building frames. These effects substantially alter performance level of the building model resting on soil classes De and Ee from life safe to near collapse. Consequently, structural safety for the mentioned building frames could not be ensured by employing the conventional design procedure excluding SSI.
Zahrai, S.M., Abbasi, S., Samali, B. & Vrcelj, Z. 2012, 'Experimental investigation of utilizing TLD with baffles in a scaled down 5-story benchmark building', Journal of Fluids and Structures, vol. 28, no. 1, pp. 194-210.
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A tuned liquid damper (TLD) is a special type of auxiliary damping device, which relies on the sloshing of a liquid (water) in a container to counteract the forces acting on the structure. Damping in the TLD is introduced as a result of liquid sloshing and wave breaking. A conventional TLD is generally tuned to the main frequency of the building and is less efficient in other frequencies. Because of this limitation, the TLD is usually used to control the structural response of structures, which could be simulated as a SDOF structure, and mostly due to wind forces. In this paper a new kind of tuned liquid damper with some installed rotatable baffles is studied experimentally. The main idea behind installing such baffles is to compensate the effects of probable mistuning of the TLD and also it is an effort toward making the TLD more controllable, i.e. a semi-active damper. Response of a five story benchmark building was utilized to investigate the contributions of these baffles on efficiency of tuned liquid damper under dynamic and earthquake excitations. By observing the performance of TLD with baffles, the study investigates the influence of a number of parameters, include the following: baffles angles, frequency ratio, mass ratio and especially the effects of probable mistuning with changing the depth of water and orientation of baffles. The damping ratios of the building for a range of baffles angles were evaluated using logarithmic decrement technique. The results that are obtained in this paper show that the displacement and acceleration responses of the structure under the free vibration test utilizing the baffles reduced up to 2.5% and 3.9%, respectively, when compared with the case where no baffles are employed. Also the dynamic magnification factor under harmonic excitation reduced up to 2.7% proportional to baffles angles. Damping of the structure equipped with this type of TLD increased in a range of 3.93-6.38% when compared to the case of using no damper.
Du, H., Zhang, N., Samali, B. & Naghdy, F. 2012, 'Robust Sampled-Data Control Of Structures Subject To Parameter Uncertainties And Actuator Saturation', Engineering Structures, vol. 36, no. 1, pp. 39-48.
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This paper presents a robust sampled-data controller design approach for vibration attenuation of civil structures considering parameter uncertainties and actuator saturation. The parameter uncertainties belong to polytopic form and are assumed to be the
Samali, B., Dackermann, U. & Li, J. 2012, 'Location And Severity Identification Of Notch-Type Damage In A Two-Storey Steel Framed Structure Utilising Frequency Response Functions And Artificial Neural Network', Advances in Structural Engineering, An International Journal, vol. 15, no. 5, pp. 743-757.
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This paper presents a vibration-based damage identification method that utilises damage fingerprints embedded in frequency response functions (FRFs) to identify location and severity of notch-type damage in a two-storey framed structure. The proposed method utilises artificial neural networks (ANNs) to map changes in FRFs to damage characteristics. To enhance damage fingerprints in FRF data, residual FRFs, which are differences in FRF data between the undamaged and the damaged structures, are used for ANN inputs. By adopting principal component analysis (PCA) techniques, the size of the residual FRF data is reduced in order to obtain suitable patterns for ANN inputs. A hierarchy of neural network ensembles is created to take advantage of individual characteristics of measurements from different locations. The method is applied to laboratory and numerical two-storey framed structures. A number of single notch-type damage scenarios of different locations and severities are investigated. To simulate field-testing conditions, numerically simulated data is polluted with white Gaussian noise of up to 10% noise-to-signal-ratio. The results from both numerical and experimental investigations show the proposed method is effective and robust for detecting notch-type damage in structures.
Sadeghi Hokmabadi, A., Fatahi, B. & Samali, B. 2012, 'Recording inter-storey drifts of structures in time-history approach for seismic design of building frames', Australian Journal of Structural Engineering, vol. 13, no. 2, pp. 175-179.
The growing trend in the application of direct displacement-based or performance-based design, lays more emphasis on the precise prediction of design parameters such as the inter-storey drift controlling the performance level of the structure. Practising engineers employ different methods to record the inter-storey drifts in time-history approach mainly based on the maximum lateral deformation of the structure. In this study, a 15-storey concrete moment resisting building is designed using time-history analysis. Then reliability and accuracy of each method in predicting the maximum inter-storey drifts under the influence of three earthquake records, namely 1995 Kobe, 1994 Northridge and 1940 El Centro earthquakes, are investigated. Results clearly indicate that to choose the most critical drift to evaluate the performance level of structures, the absolute maximum drift over time should be calculated. Other methods based on the maximum storey deflection may result in unconservative design.
Nabavi, S., Nejadi, S. & Samali, B. 2012, 'Technical and Economical Assessment of the Corrosion Preventive Methods for Maritime Reinforced Concrete Structures', Applied Mechanics and Materials, vol. 193-194, pp. 1005-1009.
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Degradation of concrete in maritime structures has become a worldwide problem due to growing costs of its maintenance, rehabilitation; and environmental impacts. Degradation processes which decrease the service life of RC structures may influence both concrete and steel and depend strongly on diffusion processes of moisture and aggressive species such as carbon dioxide, chlorides, and sulfates from environment into the concrete as a porous media. In this study, the technical advantages and disadvantages of the most commonly corrosion preventive methods have been investigated and then cost analysis by comparing the Present Value of the methods was carried out for 40 years of life time. In cost analysis the initial cost of construction and installation; maintenance and repair cost; and operational cost for each technique have been considered. This investigation proved that the lower cost methods have not shown an acceptable performance in long term and the other methods, which have exhibited a good performance, have increased the lifetime cost of structure significantly.
Li, J., Subhani, S. & Samali, B. 2012, 'Determination of Embedment Depth of Timber Poles and Piles Using Wavelet Transform', Advances in Structural Engineering, An International Journal, vol. 15, no. 5, pp. 759-770.
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This paper presents an investigation on the wave propagation in timber poles with Wavelet Transform (WT) analysis for identification of the condition and underground depth of embedded timber poles in service. Most of non-destructive testing (NDT) applications for timber poles using wave-based methods consider only single wave mode and no dispersion. However, for wave propagations in timber poles (damaged/undamaged), such simplification may not be correct, especially for broad band excitation using impulse impact. To investigate the problem, a 5m timber pole was investigated numerically and experimentally. A dispersion curve is generated from the numerical results to provide guidance on the velocity and wave mode selection. Continuous wavelet transform (CWT) is applied on the same signal to verify the presence of modes and to process data from experimental testing. The results are presented in both time domain and time-frequency domain for comparison. The results of the investigation showed that, wavelet transform analysis can be a reliable signal processing tool for NDT in terms of condition and embedment length determination.
Li, J., Dackermann, U., Xu, Y.L. & Samali, B. 2011, 'Damage Identification In Civil Engineering Structures Utilizing Pca-Compressed Residual Frequency Response Functions And Neural Network Ensembles', Structural Control and Health Monitoring, vol. 18, no. 2, pp. 207-226.
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This paper presents a non-destructive, global, vibration-based damage identification method that utilizes damage pattern changes in frequency response functions (FRFs) and artificial neural networks (ANNs) to identify defects. To extract damage features and to obtain suitable input parameters for ANNs, principal component analysis (PCA) techniques are applied. Residual FRFs, which are the differences in the FRF data from the intact and the damaged structure, are compressed to a few principal components and fed to ANNs to estimate the locations and severities of structural damage. A hierarchy of neural network ensembles is created to take advantage of individual information from sensor signals. To simulate fieldtesting conditions, white Gaussian noise is added to the numerical data and a noise sensitivity study is conducted to investigate the robustness of the developed damage detection technique to noise. Both numerical and experimental results of simply supported steel beam structures have been used to demonstrate effectiveness and reliability of the proposed method.
Shrestha, R., Smith, S.T. & Samali, B. 2011, 'The effectiveness of FRP strips in repairing moderately and severely damaged RC beam-column connections', MAGAZINE OF CONCRETE RESEARCH, vol. 63, no. 9, pp. 629-644.
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Zheng, L., He, X., Wu, Q. & Samali, B. 2011, 'A system for licence plate recognition using a hierarchically combined classifier', International Journal of Intelligent Systems Technologies and Applications, vol. 10, no. 2, pp. 189-202.
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In a real time, automatic licence plate recognition system, licence detection, character segmentation and character recognition are three important components. All these three components generally require high accuracy and fast recognition speed to process. In this paper, general processing steps for license plate recognition (LPR) are addressed. After three types of combined classifiers are introduced and compared, a hierarchically combined classifier is designed based on an inductive learning-based method and an support vector machine (SVM)-based classification. This approach employs the inductive learning-based method to roughly divide all classes into smaller groups. Then, the SVM approach is used for character classification in individual groups. Having obtained a collection of samples of characters in advance from licence plates after licence detection and character segmentation steps, some known samples are available for training. After the training process, the inductive learning rules are extracted for rough classification and the parameters used for SVM-based classification are obtained. Then, a classification tree is constructed for next fast training and testing processes based on SVMs. The experimental results show that the hierarchically combined classifier is better than either the inductive learning-based classification or the SVM-based classification with a lower error rate and a faster processing speed. 2011 Inderscience Enterprises Ltd.
Jinwuth, W., Samali, B. & Wang, C.C. 2011, 'Pushover Testing of Circular Adobe Structure', Advanced Materials Research, vol. 287-290, pp. 1907-1910.
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Many unreinforced adobe or mud-brick structures have in the past suffered severe damage from seismic forces and have caused a vast number of deaths. In contrast, some adobe buildings located in seismic regions have performed well under several seismic events. Researchers noticed that most existing circular adobe houses performed well in withstanding earthquakes even though some did not have any additional ductile reinforcement. This paper presents the investigation of seismic performance of unreinforced circular adobe buildings using static pushover testing. A scaled model (1:3 scale) of adobe circular structure were built and tested by static lateral load and pushed to total collapse. The results presented in the form of capacity curves, are compared with the expected lateral loading obtained from the static tilt testing carried out in earlier research. The outcome of this research can be used to evaluate the existing circular adobe houses and can give design recommendations of suitable configurations for new circular adobe buildings
Li, Y., Li, J. & Samali, B. 2011, 'Dynamic Performance of a Novel Magnetorheological Pin Joint', Journal of System Design and Dynamics, vol. 5, no. 5, pp. 706-715.
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Magnetorheological fluid (MRF) has received significant attention lately and MRF based devices have been proposed for structural control applications in recent years. The unique characteristics of MR fluid lies in its abilities to reversibly, repeatedly and instantly change from a free flowing liquid to a semi-solid state when exposed to a magnetic field. The electric power required to drive the MR devices can be easily provided by a battery. Possessing such unique properties, MR fluid based devices, such as MR damper, have become promising candidates in the semi-active control for civil structure applications. However, most of the published research has focused on application of MR dampers instead of exploring other type of MR devices. In addition, MR based devices exhibit complex nonlinear hysteresis behaviour and thus making their modelling a challenging task. In this paper, a novel MR fluid based device, namely MR pin joint, is proposed as a smart structural member in development of an intelligent civil structure that can suppress unwanted vibrations to ensure safety and serviceability of the structure. After design and fabrication, experiments have been conducted to characterise dynamic behaviours of the new device under different harmonic excitations with various input currents. Response time of the MR pin joint is compared when the MR pin joint is driven under different applied currents and moving speeds. Test data shows that the MR pin joint possesses a unique behaviour in the moment-angular velocity plot. A hyperbolic hysteresis model is proposed to model such unique behaviour. The investigation presented in the paper explores dynamic performance of MR pin joint. Finally, a parametric model is developed following the investigation on the correlation of coefficients in the proposed model with the loading conditions and applied currents.
Dackermann, U., Li, J. & Samali, B. 2010, 'Dynamic-Based Damage Identification Using Neural Network Ensembles and Damage Index Method', Advances In Structural Engineering, vol. 13, no. 6, pp. 1001-1016.
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This paper presents a vibration-based damage identification method that utilises a damage fingerprint? of a structure in combination with Principal Component Analysis (PCA) and neural network techniques to identify defects. The Damage Index (DI) method is used to extract unique damage patterns from a damaged beam structure with the undamaged structure as baseline. PCA is applied to reduce the effect of measurement noise and optimise neural network training. PCA-compressed DI values are, then, used as inputs for a hierarchy of neural network ensembles to estimate locations and severities of various damage cases. The developed method is verified by a laboratory structure and numerical simulations in which measurement noise is taken into account with different levels of white Gaussian noise added. The damage identification results obtained from the neural network ensembles show that the presented method is capable of overcoming problems inherent in the conventional DI method. Issues associated with field testing conditions are successfully dealt with for numerical and the experimental simulations. Moreover, it is shown that the neural network ensemble produces results that are more accurate than any of the outcomes of the individual neural networks.
Samali, B., Li, J., Choi, F.C. & Crews, K. 2010, 'Application of the damage index method for plate-like structures to timber bridges', Structural Control and Health Monitoring, vol. 17, no. 8, pp. 849-871.
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The paper presents a research recently completed by the authors utilizing a method of damage evaluation for identifying damage in timber bridges, numerically and experimentally. The method utilizes changes in modal strain energy between the undamaged and damaged states of plate-like structures. A finite element model of a laboratory timber bridge was developed to investigate the capabilities and limitations of the method to detect damage. A simple four-girder bridge was fabricated and tested in a laboratory to verify the method. The numerical studies showed that the method can correctly identify single and multiple damage locations within the bridge. The experimental studies also showed promising results for detecting severe damage, but less effective for light and medium damage. Copyright 2009 John Wiley & Sons, Ltd.
Samali, B., Crews, K.I., Aboura, K. & Li, J. 2009, 'The Use of Stochastic Processes in Bridge Maintenance Optimisation', African Journal of Information & Communication Te..., vol. 5, no. 1, pp. 43-53.
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We introduce an approach for modelling the structural deterioration of components of bridges for maintenance optimization purposes. The Markov chain model is found in the maintenance and repair problems since the early 60's, is introduced to the maintenance of road infrastructure in the 1980's, and is made to drive the current bridge maintenance optimization systems. While this model results into solvable programming problems and provides a solution, there are a number of criticisms associated with it. We highlight the shortfalls of the Markov model for bridge lifetime assessment and promote the use of stochastic processes.
Li, Y., Li, J., Samali, B. & Wang, J. 2009, 'Design considerations and experimental studies on semi-active smart pin joint', Frontiers of Mechanical Engineering in China, vol. 4, no. 4, pp. 363-370.
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Hostile dynamic loadings such as severe wind storms, earthquakes, and sudden impacts can cause severe damage to many civil engineering structures. An intelligent structural system equipped with smart structural members that are controllable in real-time is an effective solution to structural damage and failure during such situations. Civil intelligent structures with controllable properties to adapt to any changes due to dynamic loadings can lead to effective protection of structures and their occupants. In this paper, design and testing of a semi-active magnetorheological (MR) pin joint, in which the moment resistance can be controlled in real-time by altering the magnetic field, is reported with the view of using it as a potential candidate for smart members in the development of intelligent structures. Design of prototype smart pin joints includes theoretical analysis related to the radius of the rotary plate, the property of MR fluids and the gap between the rotary plate and the casing based on the requirements of the dynamics of MR pin joints. FEM analysis was deployed to study the distribution of the magnetic field along the gap. It is found, from the theoretical analysis and experimental verification, that the MR pin joint with a diameter of 180 mm can produce a torque of up to 30 Nm, which meets requirements for semi-active members in a multi-storey prototype building model in the next stage of research and development. Higher Education Press and Springer-Verlag 2009.
Dackermann, U., Li, J. & Samali, B. 2009, 'Damage Identification in Timber Bridges Utilising the Damage Index Method and Neural Network Ensembles', Australian Journal of Structural Engineering, vol. 9, no. 3, pp. 181-194.
Many of Australia's timber bridges are in aged and decayed conditions. In order to ensure the reliability of these structures and the safety of the public, condition assessment, damage detection and safety evaluation is necessary. This paper presents a damage identification procedure, which is based on global change of vibration characteristics of a structure. The developed method utilises the damage index (DI) method in combination with neural network techniques to identify damage in numerical and experimental timber beam structures. The neural network ensemble approach is utilised in order to respect important diversities of different modes and to integrate individual characteristics of vibrational mode separated damage features. The method considers field testing issues associated with measurement noise, limited number of sensor arrays and environmental fluctuations. The results of damage detection using the proposed approach demonstrate its ability to determine the location and severity of all present damage cases. The outcomes show that the developed damage detection method is effective, robust and reliable.
Shrestha, R., Smith, S.T. & Samali, B. 2009, 'Strengthening RC beam-column connections with FRP strips', PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-STRUCTURES AND BUILDINGS, vol. 162, no. 5, pp. 323-334.
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Samali, B., Dowling, D.M. & Li, J. 2008, 'Dynamic testing and analysis of adobe-mudbrick structures', Australian Journal of Structural Engineering, vol. 8, no. 1, pp. 63-75.
Traditional, unreinforced adobe-mudbrick houses are highly susceptible to damage and destruction during seismic events. Research at the University of Technology Sydney has included shake table testing of 10 scale model (1:2) u-shaped adobe wall units to assess the performance of different reinforcement systems and evaluate the response to out-of-plane seismic forces. This paper describes the qualitative and quantitative performance of one unreinforced and two reinforced adobe structures. Results confirm the importance of using appropriately time-scaled input spectra to ensure dynamic similitude and induce damaging near-resonance conditions. The testing and analysis revealed both internally and externally reinforced structures to be effective at impeding initial cracking, as well as delaying major structural damage and ultimate collapse. The system incorporating external vertical reinforcement performed significantly better and has the clear advantage of being simpler to construct, as well as being a viable option for the retrofit-strengthening of existing dwellings. Institution of Engineers Australia, 2008.
Ha, Q.P., Kwok, N.M., Nguyen, M.T., Li, J. & Samali, B. 2008, 'Mitigation of seismic responses on building structures using MR dampers with Lyapunov-based control', STRUCTURAL CONTROL & HEALTH MONITORING, vol. 15, no. 4, pp. 604-621.
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Samali, B., Dowling, D.M. & Li, J. 2008, 'Static and dynamic testing of adobe-mudbrick structures', Australian Journal of Structural Engineering, vol. 8, no. 2, pp. 159-170.
Each decade major earthquakes highlight the vulnerability of traditional adobemudbrick houses, especially in developing countries. This paper describes two series of tests (static and dynamic) designed to investigate simple and effective methods of improving the structural capacity of adobe-mudbrick buildings. The static tests presented in this paper include compressive, shear and flexural bond strength testing, and consider a variety of simple modifications to the brick laying technique (effects of brick surface moisture content, mortar thickness and curing load). Results show that a significant improvement in the shear and flexural bond strength of adobe-mudbrick masonry can be practically achieved by wetting the surface of each brick prior to laying, using a thin mortar joint and applying a normal load during curing. The dynamic testing component of this paper provides a summary of the shake table testing of 10 u-shaped adobe wall units, and details the preparation and testing of a 1:2 scale model house that was retrofit-strengthened with vertical bamboo poles, horizontal wire and a timber ring beam. Results confirm that these additions, when securely tied together, create an integrated matrix that restrains movement and enhances the overall strength of the structure. The model house performed extremely well, even during repeated high intensity shake table testing, with catastrophic failure and collapse prevented in all cases. Institution of Engineers Australia, 2008.
Choi, F.C., Li, J., Samali, B. & Crews, K. 2008, 'Application of the modified damage index method to timber beams', Engineering Structures, vol. 30, no. 4, pp. 1124-1145.
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In this paper the use of two existing algorithms developed for global nondestructive evaluation to locate and evaluate localised damage in timber beams is investigated using a finite element model. These damage localisation algorithms were found, through this investigation, not to be effective in locating multiple damage scenarios and unable to evaluate the severity of damage. Hence, modifications on damage index algorithms as well as a hybrid algorithm are proposed to overcome the problems. In this study, experimental modal analysis (EMA) was used as a tool to extract mode shapes for calculating the damage index in the proposed method which utilises changes in modal strain energy between the undamaged and the damaged timber beam model. The modified damage index (MDI) method normalises the mode shape curvature and the hybrid algorithm combines the modified damage index and changes in flexibility algorithms which reflect the changes of natural frequency and mode shape. Analytical evaluations were performed to compare and verify the ability of original and modified damage localisation algorithms in locating single and multiple damage in timber beams. The modified damage index (MDI) algorithm and the hybrid damage algorithm are also used in the experimental studies to validate the effectiveness of the methods to locate and evaluate damage within timber beams by laboratory experiments. 2007 Elsevier Ltd. All rights reserved.
Widjaja, J.H., Samali, B. & Li, J. 2007, 'The Use of Displacement Threshold for Switching Frequency Strategy for Structural Vibration Mitigation', Journal of Mechanical Science and Technology, vol. 21, no. 6, pp. 865-869.
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Choi, F.C., Li, J., Samali, B. & Crews, K. 2007, 'Application of modal-based damage-detection method to locate and evaluate damage in timber beams', Journal of Wood Science, vol. 53, no. 5, pp. 394-400.
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Modal-based damage-detection algorithms were used to identify the location of defects commonly found in timber and to estimate their severities. In this study, the authors propose modifications to an existing damage-detection algorithm for locating and evaluating damage by comparing the modal strain energy before and after damage using the first two flexural modes of vibration. Experimental verification was performed on pin-pin supported timber beams by employing the algorithms with extracted modal parameters using experimental modal analysis. Single and multiple cases of damage used to simulate pocket(s) of rot with various severities were inflicted by removing sections of timber beam specimens. The proposed damage indicator, computed from the first two flexural modes, was capable of detecting all damage locations. It was also able to estimate, with reasonable accuracy, the severity of damage in term of loss of sectional moment of inertia. The modified damage index method is generally reliable in detecting the location and estimating the severity of simulated defects in timber beams. 2007 The Japan Wood Research Society.
Kwok, N.M., Ha, Q.P., Nguyen, M.T., Li, J. & Samali, B. 2007, 'Bouc-Wen model parameter identification for a MR fluid damper using computationally efficient GA', ISA Transactions, vol. 46, no. 2, pp. 167-179.
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A non-symmetrical Bouc-Wen model is proposed in this paper for magnetorheological (MR) fluid dampers. The model considers the effect of non-symmetrical hysteresis which has not been taken into account in the original Bouc-Wen model. The model parameters are identified with a Genetic Algorithm (GA) using its flexibility in identification of complex dynamics. The computational efficiency of the proposed GA is improved with the absorption of the selection stage into the crossover and mutation operations. Crossover and mutation are also made adaptive to the fitness values such that their probabilities need not be user-specified. Instead of using a sufficiently number of generations or a pre-determined fitness value, the algorithm termination criterion is formulated on the basis of a statistical hypothesis test, thus enhancing the performance of the parameter identification. Experimental test data of the damper displacement and force are used to verify the proposed approach with satisfactory parameter identification results. 2007 ISA.
Nguyen, T., Nguyen, M., Kwok, N., Ha, Q.P. & Samali, B. 2007, 'Magnetorheological damper semiactive control for civil structures with symmetric quantised sliding mode controllers', Journal of JSAEM, Japanese Society of Applied Electromagnetics and Mechanics, vol. 15, pp. 184-187.
Li, J., Choi, F., Samali, B. & Crews, K.I. 2007, 'Damage Localisation and Severity Evaluation of a Beam-Like Timber Structure Based on Modal Strain Energy and Flexibility Approaches', Journal of Building Appraisal, vol. 2, no. 4, pp. 323-334.
Mendis, P., Ngo, T.D., Haritos, N., Hira, A., Samali, B. & Cheung, J. 2007, 'Wind Loading on Tall Buildings', Electronic Journal of Structural Engineering, vol. 7, pp. 41-54.
Samali, B., Li, J., Crews, K.I. & Al-dawod, M. 2007, 'Load rating of impaired bridges using a dynamic method', Electronic Journal of Structural Engineering, vol. 7, pp. 66-75.
Local Government in Australia is responsible for the operational management and maintenance of over 20,000 bridges. More than 70% of these bridges comprise aging timber bridges, the load capacity and structural adequacy of many of which have been impaired over time. This is partly due to increased vehicular loads with little attention to consequence of such increases. It is now necessary to determine the load carrying capacity of these bridges using simple yet reliable methods to allow local authorities to upgrade, replace or sign post at-risk bridges. In this paper a novel dynamic based method is presented by which the in-service stiffness of the bridge is estimated first. From this stiffness the load carrying capacity of the bridge is estimated following a statistically based analysis.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2007, 'An experimental study on damage detection of structures using a timber beam', Journal Of Mechanical Science And Technology, vol. 21, no. 6, pp. 903-907.
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Using vibration methods for the damage detection and structural health monitoring in bridge structures is rapidly developing. However, very little work has so far been reported on timber bridges. This paper intends to address such shortcomings by experim
Tse, K., Kwok, K.C., Hitchcock, P., Samali, B. & Huang, M.F. 2007, 'Vibration Control Of A Wind-excited Benchmark Tall Building With Complex Lateral-torsional Modes Of Vibration', Advances In Structural Engineering, vol. 10, no. 3, pp. 283-304.
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This paper describes a proposed wind-excited benchmark tall building incorporating three-dimensional lateral-torsional modes of vibration, which is typical of a significant number of modern tall buildings. A series of wind tunnel pressure tests were cond
Samali, B., Widjaja, J. & Reizes, J. 2006, 'The controllable fluid dashpot damper performance', SMART STRUCTURES AND SYSTEMS, vol. 2, no. 3, pp. 209-224.
Al-Dawod, M., Samali, B. & Li, J. 2006, 'Experimental verification of an active mass driver system on a five-storey model using a fuzzy controller', Structural Control and Health Monitoring, vol. 13, no. 5, pp. 917-943.
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This paper reports experimental tests conducted on a five-storey model using an active mass driver (AMD) system, where the control action was achieved by using a fuzzy logic controller (FLC) and the UTS state-of-the-art shake table facility. The performance of the fuzzy controller was checked against El Centro 1940, Hachinohe 1968, Northridge 1994, and Kobe 1995 earthquakes to verify the potential of using the fuzzy controller in real applications for active control of structures. Fuzzy logic is one of few mathematical model-free approaches to system identification and control. Other advantages of fuzzy logic controllers are that they can be nonlinear, adaptive, admit a high degree of parallel implementation, and tolerate uncertainty in the system. The building model under consideration is a large-scale five-storey, 3.6-m-tall, steel frame designed and manufactured at the University of Technology, Sydney. The paper details the experimental set up of the five-storey model with AMD system and the instrumentation used to measure the response, the design process of the Fuzzy Controller, and the earthquake excitations used in the experimental tests. The results of the experimental tests confirm the potential of using the adopted fuzzy controller for the active structural control using, an active mass driver (AMD) system. Copyright 2005 John Wiley & Sons, Ltd.
Kwok, N.M., Ha, Q.P., Nguyen, T.H., Li, J. & Samali, B. 2006, 'A novel hysteretic model for magnetorheological fluid dampers and parameter identification using particle swarm optimization', Sensors and Actuators, A: Physical, vol. 132, no. 2, pp. 441-451.
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Non-linear hysteresis is a complicated phenomenon associated with magnetorheological (MR) fluid dampers. A new model for MR dampers is proposed in this paper. For this, computationally-tractable algebraic expressions are suggested here in contrast to the commonly-used Bouc-Wen model, which involves internal dynamics represented by a non-linear differential equation. In addition, the model parameters can be explicitly related to the hysteretic phenomenon. To identify the model parameters, a particle swarm optimization (PSO) algorithm is employed using experimental force-velocity data obtained from various operating conditions. In our algorithm, it is possible to relax the need for a priori knowledge on the parameters and to reduce the algorithmic complexity. Here, the PSO algorithm is enhanced by introducing a termination criterion, based on the statistical hypothesis testing to guarantee a user-specified confidence level in stopping the algorithm. Parameter identification results are included to demonstrate the accuracy of the model and the effectiveness of the identification process. 2006 Elsevier B.V. All rights reserved.
Wu, H., Fitzell, B. & Samali, B. 2005, 'Control of Eccentric Building Vibration with Base Isolation', Acoustics Australia, vol. 33, no. 1, pp. 7-12.
Base isolation is found effective in reducing torsional response of structures with mass eccentricity when subjected to earthquakes. In this study, dynamic characteristics of an eccentric five-storey benchmark model, isolated with laminated rubber bearings (LRB) and lead core rubber bearings (LCRB), were examined using a shaker table and four different ground motions. The earthquake-resistant performance of LRB and LCRB isolators was evaluated. It was observed that both transverse and torsional responses were significantly reduced with the addition of an LRB or LCRB isolated system regardless of ground motion input. However, the LRB was identified to be more effective than LCRI3 in reducing relative torsional angle, model relative displacements, accelerations and angular accelerations, and therefore, provided a better protection of the superstructure and its contents.
Samali, B., Kwok, K.C., Wood, G.S. & Yang, J.N. 2004, 'Wind tunnel tests for wind-excited benchmark building', Journal Of Engineering Mechanics-ASCE, vol. 130, no. 4, pp. 447-450.
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Samali, B., Mayol, E., Kwok, K.C., Mack, A.N. & Hitchcock, P. 2004, 'Vibration control of the wind-excited 76-story benchmark building by liquid column vibration absorbers', Journal Of Engineering Mechanics-ASCE, vol. 130, no. 4, pp. 478-485.
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Al-Dawod, M., Samali, B., Kwok, K.C. & Wong, Y. 2004, 'Fuzzy controller for seismically excited nonlinear buildings', Journal Of Engineering Mechanics-ASCE, vol. 130, no. 4, pp. 407-415.
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Yang, J.N., Agrawal, A., Samali, B. & Wu, J. 2004, 'Benchmark Problem for Response Control of Wind-Excited Tall Buildings', Journal of Engineering Mechanics, vol. 130, no. 4, pp. 437-446.
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This paper presents an overview and problem definition of a benchmark problem for the response control of wind-excited tall buildings. The building considered is a 76-story 306 m concrete office tower proposed for the city of Melbourne, Australia. The building is slender with a height to width ratio of 7.3; hence, it is wind sensitive. Wind tunnel tests for such a 76-story building model have been conducted at the University of Sydney and the results of across-wind data are used in the present benchmark problem. Either active, semiactive, or passive control systems can be installed in the building to reduce the wind response, although only an active control sample problem has been worked out to illustrate the control design. In the case of active control systems, either an active tuned mass damper or an active mass driver can be installed on the top floor. In the case of passive or semiactive systems, such as viscous dampers, viscoelastic dampers, electrorheological, or magnetorheological dampers, etc., control devices can be installed in selected story units. Control constraints and evaluation criteria are presented for the design problem. A simulation program based on the linear quadratic Gaussian technique has been developed and made available for the comparison of the performance of various control strategies.
Li, J., Samali, B. & Crews, K.I. 2004, 'Determining Individual Member Stiffness of Bridge Structures Using a Simple Dynamic Procedure', Acoustics Australia, vol. 32, no. 1, pp. 9-12.
Samali, B., Al-Dawod, M., Kwok, K.C. & Wong, Y. 2004, 'Active control of cross wind response of 76-story tall building using a fuzzy controller', Journal Of Engineering Mechanics-ASCE, vol. 130, no. 4, pp. 492-498.
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Samali, B. & Al-Dawod, M. 2003, 'Performance of a five-storey benchmark model using an active tuned mass damper and a fuzzy controller', Engineering Structures, vol. 25, no. 13, pp. 1597-1610.
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Samali, B., Al-Dawod, M. & Li, J. 2003, 'Performance of an active mass driver system on a five storey benchmark model', JSME International Journal, Series C: Mechanical Systems, Machine Elements and Manufacturing, vol. 46, no. 3, pp. 848-853.
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This paper reports the experimental tests conducted on a 5-storey benchmark model defined by Samali, using an Active Mass Driver (AMD) system, where the control action is achieved by using Fuzzy Logic controller and UTS state-of-the-art shake table facility. The performance of the Fuzzy controller is checked against Hachinohe 1968 and Northridge 1994 earthquake records as input excitation to the benchmark model. The main advantage of the Fuzzy controller is its inherent robustness and ability to handle any non-linear behaviour of the structure. The results of the experimental tests show the ability of the adopted Fuzzy controller to reduce the building responses for the two earthquake records used.
Samali, B., Wu, Y. & Li, J. 2003, 'Shake table tests on a mass eccentric model with base isolation', Earthquake Engineering & Structural Dynamics, vol. 32, no. 9, pp. 1353-1372.
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Widjaja, J.H., Samali, B. & Li, J. 2003, 'A Mathematical Hysteretic Model for ER/MR Fluid Dampers', Journal Of Engineering Mechanics-asce, vol. 129, no. 2, pp. 1459-1465.
A quasi-steady duct flow through a parallel plate model for electrorheological ~ER! and magnetorheological ~MR! fluids under shear-flow mode is investigated mathematically. To do so Herschel-Bulkley power law constitutive model for ER and MR fluid is adopted to account for postyield shear thinning or shear thickening conditions as indicated in recent research. This approach is selected in order to obtain a more flexible representation of ER or MR postyield behavior rather than using the mostly adopted Bingham plastic model. This will lead to developing a theoretical method for prediction of ER or MR force characteristics.
Widjaja, J.H., Samali, B. & Li, J. 2003, 'Electrorheological and magnetorheological duct flow in shear-flow mode using Herschel-Bulkley constitutive model', Journal Of Engineering Mechanics-ASCE, vol. 129, no. 12, pp. 1459-1465.
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Djajakesukma, S., Samali, B. & Nguyen, H.T. 2002, 'Study of a semi-active stiffness damper under various earthquake inputs', Earthquake Engineering and Structural Dynamic, vol. 31, no. 10, pp. 1757-1776.
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Semi-active sti-ness damper (SASD) is one of many semi-active control systems with the capability to mitigate the dynamic response using only a small amount of external power. The system consists of a hydraulic damper connected to the bracing frame in a selected story unit. In this paper, study of a SASD in two building models of ?ve-stories under four benchmark earthquake records is reported. The purpose of this study is to evaluate the e-ectiveness of the control system against structure type and varying earthquake inputs. Various control laws are chosen to work with SASD, such as: resetting control, switching control, linear quadratic regulator (LQR) and modi?ed LQR, and the results are compared with no control and passive control cases. Numerical results show that the use of a SASD is effective in reducing seismic responses. Control efftiveness is dependent on the type of structure and earthquake excitation. Passive control is less e-ective than other control cases as expected. Resetting control, switching control and LQR generally perform similarly in response reduction. While modified LQR is more efficient and robust compared with other control algorithms.
Wu, Y. & Samali, B. 2002, 'Shake table testing of a base isolated model', Engineering Structures, vol. 24, no. N/A, pp. 1203-1215.
Li, J., Samali, B., Ye, L. & Bakoss, S.L. 2002, 'Behaviour of concrete beam-column connections reinforced with hybrid FRP sheet', Composite Structures, vol. 57, no. N/A, pp. 357-365.
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Al-Dawod, M., Samali, B., Wong, Y. & Kwok, K.C. 2001, 'Active control of along wind response of tall building using a fuzzy controller', Engineering Structures, vol. 23, pp. 1512-1522.
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Li, J., Bakoss, S.L., Samali, B. & Ye, L. 2000, 'Reinforcement of concrete beam-column connections with hybrid FRP', Composite Structures, vol. Volume 1, no. 0, pp. 805-812.
Hitchcock, P.A., Glanville, M.J., Kwok, K.C., Watkins, R. & Samali, B. 1999, 'Damping properties and wind-induced response of a steel frame tower fitted with liquid column vibration absorbers', Journal Of Wind Engineering And Industrial Aerodynamics, vol. 83, no. 1-3, pp. 183-196.
This paper presents the results of a full-scale installation of a passive vibration absorber, called a Liquid Column Vibration Absorber (LCVA), on a 67 m high steel frame communications tower. Twenty individual bi-directional LCVA units were designed to mitigate the tower's wind-induced first mode resonant response along both of the tower's principal axes. Damping properties and wind-induced response of the tower were investigated without a LCVA system installed, with a Single LCVA (SLCVA) system installed; that is, with the natural frequency of each individual LCVA unit the same and approximately equal to the first mode natural frequency of the tower; and with a Multiple LCVA (MLCVA) system installed; that is, with the natural frequencies of each individual LCVA unit distributed about the first mode natural frequency of the tower. Both SLCVA and MLCVA systems proved to be effective methods of increasing the total structural damping of the tower, and reduced the wind-induced resonant response of the tower by up to approximately 50%.
Gao, W., Kwok, K.C. & Samali, B. 1999, 'Characteristics of multiple tuned liquid column dampers in suppressing structural vibration', Engineering Structures, vol. 21, no. 4, pp. 316-331.
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The characteristics of multiple tuned liquid column dampers (MTLCD) in suppressing structural vibration are investigated. A parametric study involving the effects of frequency range, coefficient of head loss, number of TLCDs and central frequency on the performance of MTLCD is carried out through a numerical procedure which reflects the non-linear character of the liquid motion. The advantages and disadvantage of MTLCD are discussed. It was found that the frequency range and the coefficient of head loss have significant effects on the performance of a MTLCD; increasing the number of TLCDs can enhance the efficiency of the MTLCD, but no further significant enhancement is observed when the number of TLCDs is over five. The investigation also confirmed that the sensitivity of an optimised MTLCD to its central frequency ratio is not much less than that of an optimised single TLCD to its frequency ratio, and an optimised MTLCD is even more sensitive to the coefficient of head loss (or damping). However, to maintain the same level of efficiency as an optimised single TLCD, a MTLCD offers much wider choices in both frequency ratio and coefficient of head loss. In this sense, a MTLCD is more robust than a single TLCD
Hitchcock, P., Kwok, K.C., Watkins, R. & Samali, B. 1997, 'Characteristics Of Liquid Column Vibration Absorbers (lcva) .2.', Engineering Structures, vol. 19, no. 2, pp. 135-144.
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An investigation is undertaken into the bidirectional configuration of the liquid column vibration absorber (LCVA), in which the horizontal and vertical columns may have different cross-sectional areas depending on performance requirements. The bidirectional LCVA appears as a rectangular annulus in plan and mitigates the vibrations of a structure free to move in the horizontal plane by the gravitational restoring force acting on displaced LCVA liquid, energy dissipation occurring through the viscous interaction between the rigid LCVA container and the LCVA liquid, as well as transition effects which occur as the liquid moves between the horizontal and vertical columns of the LCVA. The performance of various configurations of the bidirectional LCVA are studied experimentally when installed on a primary structure subjected to external sinusoidal loading. A theoretical model of the response of the primary structure is presented in which the LCVA is modelled as an equivalent solid mass vibration absorber (SIVIVA) and is found to agree with experimental data. The parameters which allow optimization of the performance of the bidirectional LCVA are investigated, and methods allowing their prediction and control are also presented.
Gao, H., Kwok, K.C. & Samali, B. 1997, 'Optimization Of Tuned Liquid Column Dampers', Engineering Structures, vol. 19, no. 6, pp. 476-486.
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The effectiveness of a tuned liquid column damper (TLCD) in controlling structural vibration is studied. A numerical method is adopted to account for nonlinearity of the governing equation. Optimum parameters of the TLCD for maximum reduction of peak structural response to harmonic excitations in a wide frequency range are presented for a wide range of flexible structures. A variation of U-shaped TLCD with different cross-sectional areas in its vertical and horizontal sections is investigated. It is found that an increase in cross-sectional area ratio (vertical/horizontal) can greatly reduce the length requirement of a TLCD making it more attractive to flexible structures. A new type V-shaped TLCD is also investigated. This type of TLCD can suppress stronger vibrations such as those caused by strong wind. It is found that, like the tuned mass damper (TIVID), there is an optimum tuning ratio (damper frequency/structure frequency) for maximum reduction in response of a structure system which is independent of the excitation. The optimum coefficient of head loss will depend on the intensity of the excitation with smaller coefficient of head loss associated with stronger excitation.
Mackriell, L., Kwok, K.C. & Samali, B. 1997, 'Critical Mode Control Of A Wind-loaded Tall Building Using An Active Tuned Mass Damper', Engineering Structures, vol. 19, no. 10, pp. 834-842.
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The active control of the first mode of vibration of two slender, wind-loaded buildings, one 200 m tall, the other 400 m, is studied. The control is applied to the buildings via an active tuned mass damper located at the top of the building. An algorithm using acceleration feedback from the top of each building is used, as is a range of empirical algorithms using some combination of feedback from the first mode of vibration of the buildings. For both buildings, it is the more critical cross-wind response which is studied, and the response is reduced to a level acceptable for human comfort. All the algorithms provide the required control using achievable control forces; however, the algorithms using pure acceleration feedback produce the best control performance for both buildings. This is because acceleration feedback combines in the most efficient way with the passive control inherent in a hybrid control system.
Hitchcock, P., Kwok, K.C., Watkins, R. & Samali, B. 1997, 'Characteristics Of Liquid Column Vibration Absorbers (lcva) .1.', Engineering Structures, vol. 19, no. 2, pp. 126-134.
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An investigation is undertaken into the passive vibration absorber called the liquid column vibration absorber (LCVA). The vibrational energy of a tall building or other structure is absorbed through the motion of a rigid LCVA container exciting the liquid contained within a LCVA, and dissipated through the viscous interaction between a rigid LCVA container and the LCVA liquid, as well as through transition effects which occur as the liquid moves between th e vertical and horizontal columns of a LCVA. The horizontal and vertical columns of a LCVA may have different cross-sectional areas depending on performance requirements. The characteristics of unidirectional LCVAs are investigated, and found to be dependent on the geometrical configuration of a LCVA. Methods allowing prediction and control of these characteristics are also presented.
Samali, B. & Kwok, K.C. 1995, 'Use Of Viscoelastic Dampers In Reducing Wind-induced And Earthquake-induced Motion Of Building Structures', Engineering Structures, vol. 17, no. 9, pp. 639-654.
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Viscoelastic (VE) dampers have been successfully incorporated in a number of tall buildings as a viable energy dissipating system to suppress wind- and earthquake-induced motion of building structures. This type of damper dissipates the building's mechanical energy by converting it into heat. Several factors such as ambient temperature and the loading frequency will affect the performance and hence the effectiveness of the damper system. VE dampers have been able to increase the overall damping of the structure significantly, hence improving the overall performance of dynamically sensitive structures. The effectiveness of VE dampers has been demonstrated both experimentally and analytically by many researchers over the past 25 years. The twin towers of the World Trade Center Buildings in New York City and the Columbia SeaFirst Building in Seattle, Washington, are among the first buildings which benefited from the installation of VE dampers. In seismic applications, the VE dampers can be incorporated either into new construction or as a viable candidate for the retrofit of existing buildings which adds to the versatility of VE dampers.
Kwok, K.C. & Samali, B. 1995, 'Performance Of Tuned Mass Dampers Under Wind Loads', Engineering Structures, vol. 17, no. 9, pp. 655-667.
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The performance of both passive and active tuned mass damper (TMD) systems can be readily assessed by parametric studies which have been the subject of numerous research. The results of those parametric studies are invaluable in the selection of optimum TMD parameters. Few experimental verifications of TMD theory have been carried out, particularly those involving active control, but the results of those experiments generally compared well with those obtained by parametric studies. Despite some serious design constraints, a number of passive and active tuned mass damper systems have been successfully installed in tall buildings and other structures to reduce the dynamic response due to wind and earthquakes. The results of extensive full-scale measurement programs conducted on a significant number of these clearly show the effectiveness of the systems.
Facioni, R., Kwok, K.C. & Samali, B. 1995, 'Wind-tunnel Investigation Of Active Vibration Control Of Tall Buildings', Journal Of Wind Engineering And Industrial Aerodynamics, vol. 54-55, pp. 397-412.
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An active tuned mass damper (ATMD) installed in the top of a rectangular model building was tested in a wind tunnel for its effectiveness in suppressing cross-wind building vibrations. The ATMD was controlled using a sub-optimal control algorithm. Certain parameters critical to the operation of the ATMD were varied to observe how the ATMD's effectiveness would be altered. The ATMD was found to be effective in reducing cross-wind vibrations. The vibration in design parameters of the ATMD resulted in different levels of reduction.
Xu, Y.L., Kwok, K.C.S. & Samali, B. 1992, 'Control of wind-induced tall building vibration by tuned mass dampers', Journal of Wind Engineering and Industrial Aerodynamics, vol. 40, no. 1, pp. 1-32.
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Wind tunnel model tests and theoretical analyses were conducted to investigate the effectiveness of tuned mass dampers in suppressing wind-induced tall building motion. The tall building model was a 1:400 scale aeroelastic model of the CAARC Standard Tall Building. This model and the tuned mass damper models of different parameters were designed and tested in a wind tunnel with properly simulated atmospheric boundary layer flow. The aeroelastic test of the CAARC model demonstrated the effectiveness of the tuned mass damper system in suppressing the dynamic response of the building. The parametric study of passive tuned mass dampers, leading to theoretical analysis and design of an effective and efficient tuned mass damper system, was based on excitation spectra which were directly measured from the wind tunnel model tests. Semi-analytical results were in good agreement with the test results. The analytical results further indicated that the effectiveness of tuned mass dampers can be enhanced by the inclusion of an active control system. 1992.
Xu, Y.L., Kwok, K.C.S. & Samali, B. 1992, 'The effect of tuned mass dampers and liquid dampers on cross-wind response of tall/slender structures', Journal of Wind Engineering and Industrial Aerodynamics, vol. 40, no. 1, pp. 33-54.
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An investigation is made of the possible application of tuned liquid column dampers (TLCD) and tuned liquid column/mass dampers (TLCMD) in reducing the cross-wind response of wind-sensitive structures. The structure is modelled as a lumped mass multi-degree-freedom system taking into account both bending and shear. The cross-wind wake excitation is modelled as a stochastic process which is stationary in time and non-homogeneous in space. A random vibration analysis utilising transfer matrix formulation is carried out to obtain response statistics. The nonlinear damping term in the fundamental equation of the tuned liquid damper is treated by an equivalent linearization technique. Numerical examples show that tuned liquid dampers, which have significant practical advantages, can achieve the same motion reduction level as the traditional tuned mass dampers if the parameters of the liquid dampers are properly selected. However, excessive liquid motion in a tuned liquid column/mass damper may reduce the effectiveness of this damper and therefore a careful selection of the frequency tuning ratios of the damper is necessary. 1992.
Xu, Y.L., Kwok, K.C.S. & Samali, B. 1992, 'Torsion response and vibration suppression of wind-excited buildings', Journal of Wind Engineering and Industrial Aerodynamics, vol. 43, no. pt 3, pp. 1997-2008.
A series of wind tunnel model tests and theoretical analyses were conducted to investigate torsion excitation, response and vibration suppression of wind-excited buildings. An aeroelastic model for pure torsion vibration was developed and the aeroelastic test results were compared with those obtained by other wind tunnel test techniques. The comparison and practice indicated that this type of modelling technique can be a convenient and efficient way to explore the mechanisms of torsional excitation and predict the torsional response of tall buildings to wind after considering mode shape correction. It is also shown that tuned mass dampers were effective in suppressing the torsional vibration of the building if the parameters of the tuned mass damper were properly selected.
Xu, Y.L., Samali, B. & Kwok, K.C. 1992, 'Control Of Along-wind Response Of Structures By Mass And Liquid Dampers', Journal Of Engineering Mechanics-asce, vol. 118, no. 1, pp. 20-39.
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An investigation is made of the possible application of tuned liquid column dampers and tuned liquid column/mass dampers in reducing the along-wind response of wind-sensitive structures. The structure is modeled as a lumped mass multi-degree-of-freedom system taking into account both bending and shear. The wind turbulence is mqdeled as a stochastic process that is stationary in time and nonhomogeneous in space. A random vibration analysis utilizing transfer matrix formulation is carried out to obtain response statistics. The nonlinear damping term in the fundamental equation of the tuned liquid damper is treated by an equivalent linearization technique. Numerical examples show that tuned liquid dampers, which have significant practical advantages, are as effective as the traditional tuned mass dampers if the parameters of the liquid dampers are properly selected. However, excess liquid motion in a tuned liquid column/mass damper may reduce the effectiveness of this damper. It is also shown that the wind-induced force- and acceleration-type responses of the structure with a damper, which is usually tuned to the fundamental frequency of the structure, should involve more than one vibration mode as higher-mode responses may become as large or even larger than the controlled-mode response
Samali, B., Kim, K. & Yang, J. 1986, 'Random Vibration Of Rotating Machines Under Earthquake Excitations', Journal Of Engineering Mechanics-asce, vol. 112, no. 6, pp. 550-565.
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Random vibration of rotating machines subjected to seismic excitations is analyzed in which the six-component earthquake ground motions are modeled as nonstationary random processes. The six-component earthquake inputs including the rotational components of base excitations, result in not only nonhomogeneous excitations but also parametric excitations. Thus, the classical spectral analysis of random vibration is not applicable. Furthermore, both nonhomogeneous and parametric random excitations are correlated random processes, making the problem even more difficult to solve analytically. To date random vibration of such a complicated problem has not been investigated. The method of Monte Carlo simulation is used to simulate the six-component nonstationary earthquake ground motions and to determine the statistics of the response of rotating machines. The significance of seismic base rotations on the overall structural response is examined. A numerical example is worked out to demonstrate the methodology employed.
Samali, B., Yang, J. & Yeh, C. 1985, 'Control Of Lateral-Torsional Motion Of Wind-Excited Buildings', Journal Of Engineering Mechanics-asce, vol. 111, no. 6, pp. 777-796.
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An investigation is made of the possible application of an active mass damper control system to tall buildings excited by strong wind turbulence. The effectiveness of active control system, as measured by the reduction of the coupled lateral-torsional motions of tall buildings is studied. The wind turbulence is modeled as a stochastic process that is stationary in time but non-homogeneous in space. The problem is formulated using the transfer matrices approach, and a closed-loop control law. The random vibration analysis is carried out to determine the statistics of the building responses, the required active control forces, and mass damper displacements. The method of Monte-Carlo simulation is also employed to demonstrate the building response behavior with or without an active control system. A numerical example of a forty-story building under strong wind excitations is given to illustrate the significant reduction of the building acceleration response by use of an active mass damper control system.
Samali, B., Yang, J. & Liu, S. 1985, 'Active Control Of Seismic-Excited Buildings', Journal Of Structural Engineering-asce, vol. 111, no. 10, pp. 2165-2180.
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An investigation is made of the possible application of both the active tendon and active mass damper control systems to buildings excited by strong earthquakes. The effectiveness of both active control systems as measured by the reduction of coupled lateral-torsional motions of buildings is studied. The earthquake ground acceleration is modeled as a uniformly modulated non-stationary random process. The problem is formulated using the transfer matrices approach and a closed-loop control law. The random vibration analysis is carried out to determine the statistics of the building response and the required active control forces. The method of Monte Carlo simulation is also employed to demonstrate the building response behavior with or without an active control system. A numerical example of an eight-story building under strong earthquake excitations is given to illustrate the significant reduction of the building response by use of an actives tendon or an active mass damper control system.
Yang, J. & Samali, B. 1983, 'Control Of Tall Buildings In Along-wind Motion', Journal Of Structural Engineering-asce, vol. 109, no. 1, pp. 50-68.
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An exploratory study is made of the possible application of active control systems to tall buildings in along-wind motion. An analytical procedure is developed to compute the statistical properties of the structural response of a tall building implemented by an active control system and excited by a random wind flow which is stationary in time and nonhomogeneous in space. The problem is formulated in terms of transfer matrices and the random vibration analysis has been carried out. A numerical example of a 40-story building is given to illustrate the significant reduction of the acceleration response using either an active mass damper or an active tendon control system.
Yang, J., Lin, Y. & Samali, B. 1981, 'Coupled Motion Of Wind-loaded Multi-story Building', Journal Of Engineering Mechanics-asce, vol. 107, no. 6, pp. 1209-1226.
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