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Associate Professor Jianchun Li

Image of Jianchun Li
Deputy Head of School, School of Civil and Environmental Engineering
Core Member, Centre for Built Infrastructure Research
Interim Deputy Head of School, School of Civil and Environmental Engineering, Faculty of Engineering & Information Technology
Director, Centre for Built Infrastructure Research
BSc (BUAA), MSc (BUAA), PhD (TCD)
 
Phone
+61 2 9514 2651
Room
CB11.11.116

Research Interests

Dynamic analysis and testing; fracture mechanics

Can supervise: Yes

Book Chapters

Samali, B., Li, J., Dackermann, U. & Choi, F. 2011, 'Vibration-Based Damage Detection for Timber Structures in Australia' in Tommy H. T. Chan and David P. Thambiratnam (eds), Structural Health Monitoring in Australia, Nova Science Publishers, New York, USA, pp. 81-108.
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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 J.I Agbinya, E. Biermann, Y. Hamam, F. Rocaries, S.K. Lal (eds), Biomedical and Environmental Sensing, River Publishers, Denmark, pp. 295-316.
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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.

Conference Papers

Li, J., Li, Y., Askari, M. & Ha, Q.P. 2014, 'Future Intelligent Civil Structures: Challenges and Opportunities', ISARC 2014 Sydney, Australia, Sydney, July 2014 in The 31st International Symposium on Automation and Robotics in Construction and Mining (ISARC 2014), ed Ha, Q;.., International Association for Automation and Robotics in Construction (IAARC), Sydney, pp. 72-79.
An intelligent civil structure offers ultimate protection to its structure, contents and occupants in terms of safety and functionality against undesired dynamic loadings and structural deficiency. In this paper, the concept of the future intelligent civil structure featuring self-adaptive, selfprognostic, self-sensing, self-powering and self-repairing abilities, is proposed. A decade research efforts from Centre for Built Infrastructure Research, University of Technology Sydney, towards the development and concept proof of such intelligent structure is reviewed.
Li, Y., Li, J. & Samali, B. 2013, 'A novel adaptive base isolator utilising magnetorheological elastomer', 22nd AUSTRALIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, Sydney, Australia, December 2012 in From materials to structures: Advancement through innovation, ed Samali, B., Attard, M.M., Song, C., CRC press/Balkema, Netherlands, pp. 763-767.
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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.
Makki-Alamdari, M., Li, J. & Samali, B. 2013, 'A comparative study on the performance of the damage detection methods in the frequency domain', Australasian Conference on the Mechanics of Structures and Materials, Sydney, Australia, December 2012 in From materials to structures: Advancement through innovation, ed Samali, B., Attard, M.M., Song, C., 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', Australasian Conference on the Mechanics of Structures and Materials, Sydney, Australia, December 2012 in From materials to structures: Advancement through innovation, ed Samali, B., Attard, M.M., Song, C., 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', Australian Conference On The Mechanics Of Structures And Materials, Sydney, Australia, December 2012 in From materials to structures: Advancement through innovation - 22nd Australian Conference On The Mechanics Of Structures And Materials, ed Samali, B., Attard, M.M., Song, C., CRC press/Balkema, Netherlands, pp. 879-884.
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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 high level 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.
Dackermann, U., Li, J. & Samali, B. 2013, 'Transmissibility function analysis for boundary damage identification of a two-storey framed structure using artificial neural networks', 22nd AUSTRALIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, Sydney, Australia, December 2012 in From materials to structures: Advancement through innovation, ed Samali, B., Attard, M.M., Song, C., CRC press/Balkema, Netherlands, pp. 891-896.
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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.
Subhani, M., Li, J. & Samali, B. 2013, 'Behaviour of stress wave propagation in utility timber pole', THE 22ND AUSTRALASIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS - From Materials to Structures: Advancement through Innovation, SYDNEY, AUSTRALIA, December 2012 in From Materials to Structures: Advancement through Innovation - PROCEEDINGS OF THE 22ND AUSTRALASIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, ed Bijan Samali, Mario M. Attard & Chongmin Song, CRC PRESS / BALKEMA, UK, pp. 1077-1082.
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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.
Jiang, X., Li, Y. & Li, J. 2013, 'Design of a Novel Linear Permanent Magnet Vibration Energy Harvester', 2013 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM2013), Wollongong, Australia, July 2013 in 2013 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM2013) - Conference Proceedings, ed Technical Committee, IEEE, USA, pp. 1090-1095.
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This paper presents a novel linear tubular permanent magnet (PM) energy harvester to scavenge energy from ambient vibrations. The proposed linear PM energy harvester consists of a mover attached with PMs and a slotted stator with build-in two-phase electromagnetic coils to induce the electromagnetic induction for converting vibrations into useful electrical energy. The magnetic circuit model of the PM harvester is built to analyze the parameters about scavenging energy and used to optimize the non-dimensional geometry factors and the structural parameters in order to maximize harvested energy under given vibration and space conditions. To confirm the design, dynamic FE simulations were conducted and compared with the analytical results. Simulation results indicate that the proposed PM harvester is able to scavenge about 100 W DC power when the RMS of vibration velocity equals to 0.4 m/s. Also, the harvested power increases as the vibration velocity increasing.
Li, Y., Li, J. & Li, W. 2013, 'Design and Experimental Testing of an Adaptive Magneto-Rheological Elastomer Base Isolator', 2013 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM2013), Wollongong, Australia, July 2013 in 2013 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM2013) - Conference Proceedings, ed Technical Committee, IEEE, USA, pp. 381-386.
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Magnetorheological elastomer (MRE) is known for its field-sensitive shear modulus and damping property when it is exposed to a magnetic field. It has a great potential for the development of vibration reduction devices. Many research, mostly in mechanical engineering, have been focused on different kinds of vibration absorbers and vibration isolators, however few research addresses its potential in base isolation system in civil engineering application. The objective of this paper is to pilot the design and experimental testing of a novel device, an adaptive MRE base isolator, for the development of smart base isolation system. A large-scale design of the novel device with unique laminated structure of steel and MR elastomer layers is adopted. Detailed procedures on designing such adaptive base isolator are introduced. An innovative design on the magnetic circuit, with aim to provide strong and uniform magnetic field to the multi-layer MRES, is proposed to incorporate into the device design. Experimental investigation is conducted to examine its behavior under various cycling loadings when it is applied with different current inputs. Experimental results indicated that the force increase and the stiffness increase of the novel device are about 45% and 37%, respectively. To conclude, the MR elastomer base isolator will be a promising candidate to facilitate the development of adaptive base isolation system for civil structures.
Jiang, X., Li, Y. & Li, J. 2013, 'A piezoelectric wafer-stack vibration energy harvester for wireless sensor networks', Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems, San Diego, USA, March 2013 in Proceedings of SPIE - The International Society for Optical Engineering - Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2013, ed Jerome Peter Lynch; Chung-Bang Yun; Kon-Well Wang, SPIE, USA, pp. 1-9.
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Over the past few decades, wireless sensor networks have been widely used in civil structure health monitoring application. Currently, most wireless sensor networks are battery-powered and it is costly and unsustainable for maintenance because of the requirement for frequent battery replacements. As an attempt to address such issue, this paper presents a novel piezoelectric vibrational energy harvester to convert the structural vibration into usable electrical energy for powering wireless sensor networks. Unlike the normal cantilever beam structure, the piezoelectric harvester presented in this paper is based on the wafer-stack configuration which is suitable for applications where large force vibration occurs, and therefore can be embedded in civil structures to convert the force induced by vibration of large structures directly into electrical energy. The longitudinal mode of the piezoelectric wafer-stack was developed firstly to illustrate the force-to-voltage relationship of piezoelectric materials and to find the inter-medium force that will be used to convert vibration energy into electrical energy. Then, two electromechanical models (without and with a rectified circuit), considering both the mechanical and electrical aspects of the harvester, were developed to characterize the harvested electrical power under the external load. Exact closed-form expressions of the electromechanical models have been derived to analyze the maximum harvested power and the optimal resistance. Finally, a shake table experimental testing was conducted to prove the feasibility of the presented piezoelectric-wafer-stack harvester under standard sinusoidal loadings. Test results show that the harvester can generate a maximum 45mW (AC) or 16mW (DC) electrical power for sinusoidal loading with 40mm amplitude and 2Hz frequency, and the harvested electrical power is proportional to the levels of exciting vibrational loading.
Yan, N., Li, J., Dackermann, U. & Samali, B. 2013, 'Numerical and experimental investigations of stress wave propagation in utility poles under soil influence', Australasian Conference on the Mechanics of Structures and Materials (ACMSM 22), Sydney, Australia, December 2012 in From materials to structures: Advancement through innovation, ed Bijan Samali, Mario M. Attard, Chongmin Song, 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.
Li, Y. & Li, J. 2013, 'Development and Modeling of a Highly-Adjustable Base Isolator Utilizing Magnetorheological Elastomer', Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Snowbird, Utah, USA, September 2013 in ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, ed Aerospace Division, ASME, USA, pp. 1-8.
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This paper presents a recent research breakthrough on the development of a novel adaptive seismic isolation system as the quest for seismic protection for civil structures, utilizing the field-dependent property of the magnetorheological elastomer (MRE). A highly-adjustable MRE base isolator was developed as the key element to form smart seismic isolation system. The novel isolator contains unique laminated structure of steel and MRE 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 base isolator possesses a controllable lateral stiffness while maintaining adequate vertical loading capacity. Experimental results show that the prototypical MRE base isolator provides amazing increase of lateral stiffness up to 1630%. Such range of increase of the controllable stiffness of the base isolator makes it highly practical for developing new adaptive base isolation system utilizing either semi-active or smart passive controls. To facilitate the structural control development using the adaptive MRE base isolator, an analytical model was developed to stimulate its behaviors. Comparison between the analytical model and experimental data proves the effectiveness of such model in reproducing the behavior of MRE base isolator, including the observed strain stiffening effect.
Li, J., Li, Y., Li, W. & Samali, B. 2013, 'Development of adaptive seismic isolators for ultimate seismic protection of civil structures', Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems, San Diego, USA, March 2013 in Proceedings of SPIE - The International Society for Optical Engineering - Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2013, ed Jerome Peter Lynch; Chung-Bang Yun; Kon-Well Wang, SPIE, USA, pp. 1-12.
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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 to1630%. 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.
Jiang, X., Li, Y. & Li, J. 2012, 'A novel piezoelectric wafer-stack vibration energy harvester', 22nd AUSTRALIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, Sydney, Australia, December 2012 in From materials to structures: Advancement through innovation, ed Samali, B., Attard, M.M., Song, C., CRC press/Balkema, Netherlands, pp. 399-404.
Piezoelectric vibration-based energy harvesters are attractive as inexhaustible replacements for batteries in low-power requirement wireless electronic devices and thus have received increasing research interest in the last few years. This paper presents a novel piezoelectric harvester based on the wafer-stack configuration to convert the external vibration into usable electrical energy for this purpose. Both analytical and experimental investigations are undertaken at University of Technology Sydney. Firstly, an electromechanical model with a rectified circuit, considering both the mechanical and electrical factors of the harvester, is built to characterise the harvested electrical power across the external loadings. Exact closed-form expressions of the electromechanical model have been given to analyse conditions for maximum harvested power. Finally, a shake table experimental testing was conducted to evaluate the feasibility of the presented PZT wafer stack harvester under standard sinusoidal loadings. Test results show that the harvester can generate a maximum 16mW electrical power for sinusoidal loading with 40mm amplitude and 2 Hz frequency.
Huang, S., Li, J., Samali, B. & Zobec, M. 2012, 'An experimental investigation of a thermal break composite facade mullion section', 22nd AUSTRALIAN CONFERENCE ON THE MECHANICS OF STRUCTURES AND MATERIALS, Sydney, Australia, December 2012 in From materials to structures: Advancement through innovation, ed Samali, B., Attard, M.M., Song, C., CRC press/Balkema, Netherlands, pp. 513-517.
This paper presents the experimental investigation into the behaviour of a typical thermal break composite fa+ade 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 (23+C), low temperature (++20+C) and high temperature (80+C). 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.
Zad, A.A., Li, J., Samali, B. & Crews, K.I. 2011, 'Finite element evaluation of non-destructive testing methods for embedded timber poles in service', Australasian Conference on the Mechanics of Structures and Materials, Melbourne, Australia, December 2010 in Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), ed Sam Fragomeni, Srikanth Venkatesan, Nelson T.K. Lam, Sujeeva Setunge, CRC Press/Balkema, The Netherlands, pp. 909-914.
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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 offactors 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 ofa free-end timber pole without embedment was 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.
Li, Y., Li, J. & Samali, B. 2011, 'Design of new generation magnetorheological pins', Australasian Conference on the Mechanics of Structures and Materials, Melbourne, Australia, December 2010 in Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), ed Sam Fragomeni, Srikanth Venkatesan, Nelson T.K. Lam, Sujeeva Setunge, CRC Press/Balkema, The Netherlands, pp. 807-812.
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Recently, research and development of smart materials and structures for civil engineering applications have attracted increasing attentions from researchers around the world. 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. Tills 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.
Dackermann, U., Li, J. & Samali, B. 2011, 'Identification of added mass on a two-storey framed structure utilising FRFs and ANNs', Australasian Conference on the Mechanics of Structures and Materials, Melbourne, Australia, December 2010 in Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), ed Sam Fragomeni, Srikanth Venkatesan, Nelson T.K. Lam, Sujeeva Setunge, CRC Press/Balkema, The Netherlands, pp. 757-762.
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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., Li, J., Crews, K.I. & Choi, F. 2011, 'Damage evaluation of a repaired timber beam using modal-based method', Australasian Conference on the Mechanics of Structures and Materials, Melbourne, Australia, December 2010 in Incorporating Sustainable Practice in Mechanics of Structures and Materials - Proceedings of the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21), ed Sam Fragomeni, Srikanth Venkatesan, Nelson T.K. Lam, Sujeeva Setunge, CRC Press/Balkema, The Netherlands, pp. 751-755.
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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.
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, Lisbon, June 2011 in International Conference on Structural Health Assessment of Timber Structures, ed Saporiti Machado, Jose; Palma, Pedro; Louren+o, Paulo B., Laboratorio Nacional de Engenharia Civil, Lisboa, Portugal, pp. 63-71.
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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.
Saleh, A., Li, J. & Lucas, M.J. 2011, 'Internet-hosted assessment system for effective teaching and enhanced learning for engineering subjects', AAEE - Annual Conference of Australasian Association for Engineering Education, Fremantle, WA, December 2011 in Proceedings of the 22nd Annual Conference for the Australasian Association for Engineering Education (AAEE2011) - Developing Engineers for Social Justice: Community Involvement, Ethics & Sustainability, ed Yasir M. Al-Abdeli & Euan Lindsay, Engineers Australia, Australia, pp. 505-509.
Despite of their popularity, online Learning Management Systems suffer serious limitations as a reliable and effective assessment tool in their implementation for engineering education, partly due to their demand for equation manipulation and multiple stage problem solving. An innovative spreadsheet based assessment tool (e-Task) which is designed to overcome such shortcoming and provides effective teaching and enhanced learning for engineering subjects has been proposed by the authors. The tool was developed for both formative and summative assessments with a capability to automatically collect not only results but also feedback from students on their perceived learning. Building on the previous work, this paper presents a further development by introducing a new deployment concept of the e-Task through internet-hosting of the system in order to enable effective teaching and enhanced learning of engineering subjects. The proposed internet-hosted assessment system (e-Task) integrates state-of-the-art cloud computing technology by incorporating a spreadsheet-like environment that can accommodate a wider range of users and course developers as well as enables easier expansion of the system in the future. It greatly enhances the fundamental concepts proposed in the original e-Taks by offering better accessibility, flexibility and controllability. It obviates any need of a specific software or hardware for the operational platform and requires only Internet access for its operation. Features of the Internet hosted e-Task include: the ability to access it by various Internet browsers, embedding learning and diagnostic feedback, individualised data sets for each students and automated marking & feedback.
Subhani, M., Li, J., Samali, B. & Dackermann, U. 2011, 'Determinations of Stress Wave Velocity in a Timber Pole using Wavelet Transform', Dynamics for Sustainable Engineering, Hong Kong, December 2011 in Proceeding of The 14th Asia Pacific Conferance, ed Law, S; Cheng, L; Xia, Y; SU, Z, The Hong Kong Polytechnic University, Hong Kong, pp. 222-231.
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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.
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', Dynamics for Sustainable Engineering, Hong Kong, December 2011 in Proceeding of The 14th Asia Pacific Conferance, ed Law, S; Cheng, L; Xia, Y; SU, Z, The Hong Kong Polytechnic University, Hong Kong, pp. 338-347.
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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.
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', East Asia-Pacific Conference on Structural Engineering and Construction, Hong Kong, January 2011 in Procedia Engineering: The Proceedings of the Twelfth East Asia-Pacific Conference on Structural Engineering and Construction + EASEC12, ed NA, 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.
Saleh, A. & Li, J. 2010, 'Innovative Assessment and Feedback System for Structural Engineering Education', Annual Conference of Australasian Association for Engineering Education, Sydney, Australia, December 2010 in Proceedings of the 21st Annual Conference for the Australasian Association for Engineering Education, ed Anne Gardner and Lesley Jolly, University of Technology, Sydney, Sydney, Australia, pp. 315-321.
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Commercial Online course management platforms are increasingly used in teaching and learning in many disciplines. However their use for setting assessment tasks in engineering education is often difficult and limited in achieving desired teaching and learning objectives. This is partly due to the nature of engineering exercise problems which often requires equation manipulation and multi-stage problem solving. This paper presents an innovative spreadsheet based tool which is designed to cater for this type of problem. The tool was developed for both formative and summative assessments and with a resource optimal capability to automate both marking and collecting timely feedback from students on their perceived learning. It aims to encourage active learning with activatable hints and to minimise plagiarism by generating individual assignment data for each student.
Li, J., Samali, B. & Xu, Y. 2009, 'A new model based damage detection approach utilising added mass', Australasian Conference on the Mechanics of Structures and Materials, Toowoomba, Australia, December 2008 in Future in Mechanics of Structures and Materials, Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, ed Aravinthan, T; Karunasena, W; Wang, H, CRC Press Taylor and Francis Group, UK, pp. 789-794.
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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, ie, 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 ++inservice+ 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.
Aboura, K., Samali, B., Crews, K.I. & Li, J. 2009, 'Stochastic Processes for Modelling Bridge Deterioration', Australasian Conference on the Mechanics of Structures and Materials, Toowoomba, December 2008 in Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, ed TBC, Taylor and Francis Group, London, pp. 533-538.
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Traditionally, bridge management systems were designed using Markov chain models.
Li, Y., Li, J., Samali, B. & Wang, J. 2009, 'Theoretical and Experimental Studies on Semi-Active Smart Pin Joint', Australasian Conference on the Mechanics of Structures and Materials, Toowoomba, Queensland, Australia, December 2008 in Future in Mechanics of Structures and Materials, Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, ed Thiru Aravinthan; Warna (Karu) Karunasena; Hao Wang, Taylor & Francis Group, USA, pp. 723-736.
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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 180mm 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.
Wang, Y., Li, J., Samali, B. & Sri Ravindrarajah, R. 2008, 'A New Damage Detection Method for Reinforced Concrete Beams Based on Modal Strain Energy', International Conference on Motion and Vibration Control, Munich, September 2008 in Proceedings of the 9th International Conference on Motion and Vibration Control, ed TBA, Technische Universitaet Muenchen, Germany, pp. 1-10.
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Choi, F., Li, J., Samali, B. & Crews, K.I. 2008, 'Non Destructive Testing of a Timber Beam using Vibration-Based Approach', Munich, September 2008 in The 9th International Conference on Motion and Vibration Control, ed Ulbrich H, et al, Technique Universaetet, Germany.
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, Varena, Italy, September 2008 in On-Site Assessment of Concrete, Masonry and Timber Structures - Volume 2, ed Binda,L; di Prisco, M; Felicetti, R, RILEM Publications, France, pp. 1125-1135.
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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.
Dackermann, U., Li, J., Samali, B., Choi, F. & Crews, K.I. 2008, 'Variation-Based Damage Identification in Civil Engineering Structures Utilising Artificial Neural Networks', Edinburgh, June 2008 in Proc. Structural Faults & Repairs 2008 12th International Conference, ed Forde, M.C, Engineering Technics Press, Endinburgh, pp. 132-132.
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', On Site Assessment of Concrete, Masonry and Timber Structures, Italy, September 2008 in Proc. SACOMATIS 2008, ed Binda, L: De Prisco, M: R Felicetti, RILEM Publications, France, pp. 1049-1058.
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Dackermann, U., Li, J. & Samali, B. 2008, 'Damage Index Method for Damage Identification Utilising Artificial Nerual Networks', Munich, September 2008 in Proc. MOVIC 2008, ed Ulbraich, H et.al, MOVIC, Germany, pp. 1-10.
Dackermann, U., Li, J. & Samali, B. 2008, 'Structural damage identification utilising PCA-compressed frequency response functons and neural network ensembles', Australasian Conference on the Mechanics of Structures and Materials, Toowoomba, December 2008 in Future in Mechanics of Structures and Materials, Proceedings of the 20th Australasian Conference on the Mechanics of Structures and Materials, ed Arivanthan, Karunasena & Wang, CRC Press, Taylor & Francis Group, London, pp. 803-809.
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Samali, B., Li, J. & Aboura, K. 2008, 'Monitoring Bridge Deterioration using sensors', International Conference of Broadband Communication, Information Technology and Biomedical Applications, Pretoria, South Africa, November 2008 in Proceedings of the Third International Conference on Broadband Communications, Information Technology & Biomedical Applications, ed Agbinya J.I, IEEE, USA, pp. 64-69.
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Structural health monitoring is a vital part in the management of bridges, particularly 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.
Aboura, K., Samali, B., Crews, K.I. & Li, J. 2008, 'Stochastic Deterioration Processes for Bridge Lifetime Assessment', International Conference of Broadband Communication, Information Technology and Biomedical Applications, Pretoria, South Africa, November 2008 in Proceedings of the Third International Conference on Broadband Communications, Information technology & Biomedical Applications, ed Agbinya, J.I., IEEE, USA, 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.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2008, 'Overview of Dynamic Based Damage Detection of Timber Bridges', 12th International Conference STRUCTURAL FAULTS & REPAIR-2008, Edinburgh, Scotland, June 2008 in Proceedings of 12th International Conference STRUCTURAL FAULTS & REPAIR-2008, ed Professor M C Forde, 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.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2007, 'Damage Evaluation of a timber Beam Using a Modal-based Method', Australasian Conference on the Mechanics of Structures and Materials, Christchurch, New Zealand, November 2006 in Proceeding of the 19th Australasian Conference on the Mechanics of Structures and Materials - Progress in Mechanics of Structures and Materials, ed Moss, P. Dhakal, R., Taylor and Francis, Leiden, Netherlands, pp. 1005-1010.
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Li, J., Choi, F. & Samali, B. 2007, 'Modal-based damage identification methods for plate-like structures', Australasian Conference on the Mechanics of Structures and Materials, Christchurch, New Zealand, November 2006 in Proceedings of the 19th Australasian Conference on the Mechanics of Structures and Materials - Progress in Mechanics of Structures and Materials, ed Moss, P. Dhakal, R., Taylor and Francis, Leiden, Netherlands, pp. 909-914.
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Li, J., Samali, B. & Crews, K.I. 2007, 'A cost effective approach for integrity assessment of timber bridges', Australasian Conference on the Mechanics of Structures and Materials, Christchurch, New Zealand, November 2006 in Proceedings of the 19th Australasian Conference on the Mechanics of Structures and Materials - Progress in Mechanics of Structures and Materials, ed Moss, P. Dhakal, R., Taylor and Francis, Leiden, Netherlands, pp. 1037-1042.
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Nguyen, M., Kwok, N., Ha, Q.P., Li, J. & Samali, B. 2007, 'Semi-active direct control of civil structure seismic responses using magneto-rheological dampers', International Symposium on Automation and Robotics in Construction, Kochi, India, September 2007 in Proceedings of the 24th International Symposium on Automation and Robotics in Construction (ISARC 2007), ed Construction Automation Group, IIT Madras, Lokavani Southern Printers, Chennai, India, pp. 157-162.
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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', Australasian Congress on Applied Mechanics, Brisbane, Australia, December 2007 in Proceedings of the 5th Australasian Congress on Applied Mechanics, ACAM 2007, ed Veidt, M; Albermani, F; Daniel, B; Griffiths, J; Hargreaves, D; McAree, P; Meehan, P; Tan, A, Engineers Australia, Australia, pp. 114-119.
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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, T., Kwok, N., Ha, Q.P., Li, J. & Samali, B. 2006, 'Adaptive sliding mode control for civil structure using magnetorheological dampers', International Symposium of Automation and Robotics in Construction, Tokyo, Japan, October 2006 in Proceedings 23rd International Symposium on Automation and Robotics in Construction, ed N/A, Japan Robot Association, Tokyo, Japan, pp. 636-641.
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Kwok, N., Nguyen, T., Ha, Q.P., Li, J. & Samali, B. 2006, 'Parameter Identification for a simple MR Damper model using Particle Swarm Optimisation', Asia Pacific Symposium on Applied Electromagnetics and Mechanics, Sydney, Australia, July 2006 in Disgest Book of the Asia Pacific Symposium on Applied Electromagnetic and Mechanics, ed n/a, 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', Asia Pacific Symposium on Applied Electromagnetics and Mechanics, Sydney, Australia, July 2006 in Digest Book of the Asia-Pacific Symposium on Applied Electromagnetics and Mechanics, ed n/a, 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, Newcastle, Australia, September 2005 in Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building Into the Future, ed Steward, M; Dockrill, B., 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, Newcastle, Australia, September 2005 in Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, ed Steward, M; Dockrill, B., Tour Hosts Pty Ltd, Austrlaia.
Samali, B., Dowling, D.M. & Li, J. 2006, 'Dynamic Response of U-Shaped Adobe-Mudbrick Wall Units', Australian Structural Engineering Conference, Newcastle, Australia, September 2005 in Austrlaian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building Into the Future, ed Steward, M; Dockrill, B., Tour Hosts Pty Ltd, Australia.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2006, 'Impact of Different Numerical Techniques on Damage Identification in Structures', East Asia-Pacific Conference on Structural Engineering and Construction, Bangkok, Thailand, August 2006 in Proceedings of The Tenth East Asia-Pacific Conference on Structural Engineering and Construction - Materials, Experimentation, Maintenance and Rehabilitation, ed w. Kanok-Nukulchai, Munasinghe, S., School of Engineering and Technology, Asian Institute of Technology, Pathumthani, Thailand, pp. 111-116.
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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', International Conference on Structural Faults and Repairs, Edinburgh, U.K., June 2006 in Proceedings of the Eleventh International Conference on Structural Faults and Repair 2006, ed Forde, M., Engineering Technics Press, Edinburgh, U.K., pp. 1-9.
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Li, J., Choi, F., Samali, B. & Crews, K.I. 2006, 'Damage Detection in a Timber Beam', International Conference on Structural Faults and Repair, Edinburgh, U.K., June 2006 in Proceedings of the Eleventh International Conference on Structural Faults and Repair 2006, ed Forde, M., Engineering Technics Press, Edinburgh, U.K., pp. 1-10.
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Choi, F., Samali, B., Crews, K.I. & Li, J. 2006, 'Calibration of a Laboratory Timber Bridge Finite Element Model using the Experimental Modal Data', World Conference on Timber Engineering, Portland, Oregon, USA, August 2006 in Proceedings CD of WCTE 2006 - 9th World Conference on Timber Engineering, ed Donald A. Bender, David S. Gromala, and David V. Rosowsky, 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', International Symposium on Intelligent Technologies in Tech'05, Phuket, Thailand, December 2005 in Proceedings of the 6th International Symposium on Intelligent Technologies, ed Santiprahob; Pratit, Daengdej; Jirapun, Faculty of Science and Technology, Assumption University, Bangkok, Thailand, pp. 115-122.
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 Conference, Albury, New South Wales, Australia, November 2005 in Australian Earthquake Engineering Society Proceedings of the 2005 Conference, ed Lam; N.T.K. Wilson; J.L. Butler; B., Australian Earthquake Engineering Society, Victoria, Australia, pp. 1-7.
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Samali, B., Dowling, D.M. & Li, J. 2005, 'Dynamic Testing of Unreinforced U-Shaped Adobe-Mudbrick Wall Unit', Australasian Conference on the Mechanics of Structures and Materials, Perth, Australia, December 2004 in Developments in Mechanics of Structures and Materials, ed Deeks; A.J., Hao; H., A A Balkema, London, United Kingdom, pp. 505-510.
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Samali, B., Widjaja, J.H., Li, J. & Reizes, J. 2005, 'Smart Braced Frame Systems', Australasian Conference on the Mechanics of Structures and Materials, Perth, Australia, December 2004 in Developments in Mechanics of Structures and Materials, ed Deeks; A.J., Hao; H., A. A. Balkema, London, United Kingdom, pp. 401-406.
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Samali, B., Widjaja, J.H., Li, J., Dackermann, U. & Brown, P.W. 2005, 'Amplitude Frequency Characteristics of 'Smart'-Pin Frame System', Asia Pacific Vibration Conference, Langkawi, Malaysia, November 2005 in Proceedings of the 11th Asia Pacific Vibration Conference, ed Leong; S. Abdul Rahman; R. Zin; T.C., Universiti Teknologi Malaysia, Langkawi, Malaysia, pp. 228-233.
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Samali, B., Dowling, D.M. & Li, J. 2005, 'Dynamic Response of U-Shaped Adobe-Mudbrick Wall Units', Australian Structural Engineering Conference, Newcastle, Australia, September 2005 in Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, ed Steward; M.G, Dockrill; B., Tour Hosts Pty Limited, Australia, pp. 1-9.
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Samali, B., Li, J., Dowling, D.M. & Dackermann, U. 2005, 'Experimental Modal Analysis of U-Shaped Adobe-Mudbrick Wall Units', Australian Earthquake Engineering Conference, Albury, New South Wales, Australia, November 2005 in Proceedings of the Australasian Earthquake Engineering Society Conference 2005, ed Lam; N.T.K., Wilson; J.L., Butler; B., Australian Earthquake Engineering Society, Victoria, Australia, pp. 39-1-39-7.
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Widjaja, J.H., Samali, B., Li, J. & Reizes, J. 2005, 'Seismic Structural Control Investigations Using a Prototype Magnetorheological Shear Damper', Australian Structural Engineering Conference, Newcastle, Australia, September 2005 in Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, ed Steward; M.G., Dockrill; B., Tour Hosts Pty Limited, Australia, pp. 1-11.
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Widjaja, J.H., Samali, B., Li, J. & Reizes, J. 2005, 'Dynamic Frequency De-Tuning Using Controllable Beam-Column Semi-Rigid Connections', Australasian Congress on Applied Mechanics, Melbourne, Australia, February 2005 in Proceedings of 4th Australasian Congress on Applied Mechanics, ed Xie; M, Mouritz; A, Khatibi; A.A., Gardiner, C, Chiu; W.K., Institute of Materials Engineering Australasia Ltd, North Melbourne, Australia, pp. 807-813.
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Choi, F., Samali, B., Li, J., Brown, P.W. & Dackermann, U. 2005, 'Investigation on the Dynamic Response of a Damaged Bridge', Asia Pacific Vibration Conference, Langkawi, Malaysia, November 2005 in Proceedings of the 11th Asia-Pacific Vibration Conference, ed Leong; M.S, Abdul Rahman; R, Zin; T.C., Universiti Teknologi Malaysia, Langkawi, Malaysia, pp. 274-280.
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Choi, F., Samali, B., Crews, K.I. & Li, J. 2005, 'Static and Dynamic Evaluation of Continuity Effect of Corbels in Timber Bridges', Australasian Congress on Applied Mechanics, Melbourne, Australia, February 2005 in Proceedings of 4th Australasian Congress on Applied Mechanics, ed Xie; M, Mouritz; A, Khatibi; A.A, Gardiner; C, Chiu; W.K., Institute of Materials Engineering Australasia Ltd, North Melbourne, Australia, pp. 285-292.
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Dowling, D.M., Samali, B. & Li, J. 2005, 'Seismic Improvement of Adobe-Mudbrick Walls-Comparison between Internal and External Vertical Reinforcement', Australian Earthquake Engineering Conference, Albury, Australia, November 2005 in Proceedings of the Australian Earthquake Engineering Society Conference 2005, ed Lam; N.T.K., Wilson; J.L., Butler, B., Australian Earthquake Engineering Society, Victoria, Australia, pp. 38-1-38-7.
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One of the vital tasks for engineers is to minimise life loss, injury and property damage under extreme dynamic loading. Devastating earthquakes in Asia, The Middle East, Africa and Latin America have served as recent reminders of the vulnerability of nonengineered, low-cost dwellings to seismic forces. The loss of life and livelihood is often drastic, with millions of people in the poorest communities most severely affected. Adobe (mudbrick) housing is particularly vulnerable because of its inherently brittle nature, wide-spread use, generally poor construction quality and the limited awareness of concepts of aseismic design and construction. Despite this limitation, there is little doubt that adobe will continue to be the choice construction material for the majority of the rural poor who simply cannot afford any alternative.
Dowling, D.M., Samali, B. & Li, J. 2005, 'An Improved Means of Reinforcing Adobe Walls-External Vertical Reinforcement', Sismo Adobe 2005, Arquitectura, Construccion y Convervacion de Edificaciones de Tierra en Areas Sismicas, Lima, Peru, May 2005 in Sismo Adobe 2005, ed N/A, 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', Australasian Conference on the Mechanics of Structures and Materials, Perth, Australia, December 2005 in Developments in Mechanics of Structures and Materials, ed Deeks; A.J., Hao; H., A A Balkema, London, United Kingdom, pp. 479-484.
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Li, J., Samali, B., Choi, F. & Dackermann, U. 2005, 'Damage Identification of Timber Bridge Using Vibration Based Methods', Asia Pacific Vibration Conference, Langkawi, Malaysia, November 2005 in Proceedings of the 11th Asia-Pacific Vibration Conference, ed Leong; M.S., Abdul Rahman; R, Zin; T.C., Universiti Teknologi Malaysia, Langkawi, Malaysia, pp. 662-668.
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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, Newcastle, Australia, September 2005 in Australian Structural Engineering Conference 2005: Structural Engineering - Preserving and Building into the Future, ed Steward; M.G. and Dockrill; B., Tour Hosts Pty Limited, Australia, pp. 1-11.
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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', Australasian Congress on Applied Mechanics, Melbourne, Australia, February 2005 in Proceedings of 4th Australasian Congress on Applied Mechanics, ed Xie; M, Mouritz; A, Khatibi; A. A, Gardiner; C, Chiu; W.K., Institute of Materials Engineering Australasia Ltd, North Melbourne,Australia, pp. 663-672.
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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 Society 2004 Conference, Mt Gambier, Australia, November 2004 in Australian Earthquake Engineering in the New Millenium, ed McCue, K., Griffith, M.C.and Butler, B., Australian Earthquake Engineering Society, Victoria, Australia, pp. 1-6.
Samali, B., Widjaja, J.H., Li, J. & Reizes, J. 2003, 'Magneto-rheological Shear Dampers; Quasi-static Modelling and Simulation', Asia Pacific Vibration Conference, Gold Coast, Queensland, Australia, November 2003 in Proceedings of the 10th Asia Pacific Vibration Conference, ed Prof Joseph Mathew, Queensland University of Technology, Brisbane, Australia, pp. 1-6.
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Samali, B., Djajakesukma, S., Nguyen, H.T. & Li, J. 2003, 'An Experimental Study of a Five Storey Steel Frame Using Semi-active Control System', Asia Pacific Vibration Conference, Gold Coast, Queensland, Australia, November 2003 in Proceedings of the 10th Asia Pacific Vibration Conference, ed Prof Jospeh Mathew, Queensland University of Technology, Brisbane, Australia, pp. 604-609.
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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)', Asia Pacific Vibration Conference, Gold Coast, Queensland, Australia, November 2003 in Proceedings of the 10th Asia Pacific Vibration Conference, ed Professor Joseph Mathew, Queensland University of Technology, Brisbane, Australia, pp. 451-456.
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Wu, Y., Samali, B. & Li, J. 2003, 'Seismic Response of Torsionally Sensitive Building Models', Asia Pacific Vibration Conference, Gold Coast, Queensland, Australia, November 2003 in Proceedings of the 10th Asia Pacific Vibration Conference, ed Professor Joseph Mathew, Queensland University of Technology, Brisbane, Australia, pp. 765-770.
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Li, J., Samali, B. & Crews, K.I. 2003, 'Determining Individual Member Stiffness of Bridge Structure Using a Simple Dynamic Procedure', Asia Pacific Vibration Conference, Gold Coast, Queensland, Australia, November 2003 in Proceedings of the 10th Asia Pacific Vibration Conference, ed Professor Joseph Mathew, Queensland University of Technology, Gold Coast, Queensland, Australia, pp. 379-384.
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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', London, UK, July 2003 in Abstracts of the Tenth International Conference: Structural Faults & Repair Abstracts, ed Professor M.C. Forde, ENGINEERING TECHNICS PRESS, UK.
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Li, J., Samali, B. & Chapman, C.M. 2002, 'Experimental realisation of active control of a five storey building model using SMA actuators', The 17th Australasian Conference on the Mechanics of Structures and Materials, Gold Coast, Australia, June 2002 in Advances in Mechanics of Structures and Materials, ed Loo, Y.C.; Chowdhury, S.H.; and Fragomeni, S., A.A. Balkema Publishers, Australia, pp. 699-704.
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Li, J., Samali, B. & Chapman, C.M. 2002, 'Variable structure control of seismically excited structure with shape memory alloy actuators', Australasian Congress on Applied Mechanics, Sydney, Australia, February 2002 in Applied Mechanics Progress and Applications, ed Zhang, L.; Tong, L. and Gal, J., World Scientific, Australia, pp. 665-670.
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Samali, B., Al-Dawod, M. & Li, J. 2002, 'Performance of a five storey benchmark model using an active mass driver and a fuzzy controller', Australasian Congress on Applied Mechanics, Gold Coast, Australia, February 2002 in Proceedings of the Third Australasian Congress on Applied Mechanics, ed Zhang, LingChi, TONG, LiYong, Gal, John, World Scientific Publishing, Singapore, pp. 647-652.
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Samali, B., Wu, Y. & Li, J. 2002, 'Torsional response of a base-isolated eccentric building model', The 17th Australasian Conference on the Mechanics of Structures and Materials, Gold Coast, Australia, June 2002 in Advances in Mechanics of Structures and Materials, ed Loo, Y.C.; Chowdhury, S.H.; and Fragomeni, S., A.A. Balkema Publishers, Australia, pp. 769-774.
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Wu, Y., Samali, B. & Li, J. 2002, 'Earthquake resistance performance of laminated and lead core rubber bearings', Australasian Congress on Applied Mechanics, Sydney, Australia, February 2002 in Applied Mechanics Progress and Applications, ed Zhang, L.; Tong, L. and Gal, J., World Scientific, Singapore, pp. 659-664.
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Ha, Q.P., Li, J., Hong, G. & Samali, B. 2001, 'Active structural control using dymanic output feedback sliding mode', Australasian Conference on Robotics and Automation, Sydney, November 2001 in Proceedings of the Australian Conference on Robotics and Automation ACRA'01, ed Publisher, Australian Robotics & Automation Association, Sydney, pp. 20-25.
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Journal Articles

Dackermann, U., Crews, K.I., Kasal, B., Li, J., Riggio, M., Rinn, F. & Tannert, T. 2014, 'In situ assessment of structural timber using stress-wave measurements', Materials and Structures, vol. 47, pp. 787-803.
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This paper summarizes the test recommendations for in situ assessment of structural timber using stress wave measurements as developed by members of the RILEM Technical Committee AST 215 ``In-situ assessment of structural timber++. In the first part, the basic principles, the equipment, and the practical application of stress-wave-based testing using the time-of-flight method are described. A detailed testing procedure provides hands-on information on the execution of in-field stress wave testing. A typical example is given to demonstrate step-by step on how to evaluate stress wave readings and the health state of the inspected timber member. The latter part of the paper gives a short overview of the use of acoustic tomography and ultrasonic echo methods.
Jiang, X., Wang, J., Li, Y. & Li, J. 2014, 'Design and modelling of a novel linear electromagnetic vibration energy harvester', International Journal Of Applied Electromagnetics And Mechanics, vol. 45, no. 2.
This paper presents the design and evaluation of a novel permanent magnet (PM) energy harvesting system for scavenging electrical energy from ambient vibrations. A two-phase tubular linear PM vibration energy harvester consisting of a mover attached with permanent magnets and a slotted stator with built-in two-phase electromagnetic coils is proposed to convert vibrational kinetic energy into electrical energy. Aiming at maximizing the efficiency of vibration-to-electrical energy conversion under designated vibration and limited space requirement, a systematic research, including innovative device design, theoretical modelling and analysis, and finite element evaluation on the PM vibration energy harvester will be presented in this paper. In addition, the methodology of winding the two-phase coils in slotted stator is explicated in order to fully utilize the harvested electrical energy. A two-phase rectifier circuit is developed to convert the alternative voltage generated by the PM harvester into DC voltage that can be used directly by the external resistive load. Simulation results indicate that the proposed linear PM vibration energy harvesting system is able to generate about 100 watt DC electrical power under the vibration with the velocity of 0.4 m/s and the output electrical power is proportional to the levels of vibration excitations.
Li, Y. & Li, J. 2014, 'Dynamic characteristics of a magnetorheological pin joint for civil structures', Frontiers of Mechanical Engineering, vol. 9.
Magnetorheological (MR) pin joint is a novel device in which its joint moment resistance can be controlled in real-time by altering the applied magnetic field. The smart pin joint is intended to be used as a controllable connector between the columns and beams of a civil structure to instantaneously shift the structural natural frequencies in order to avoid resonance and therefore to reduce unwanted vibrations and hence prevent structural damage. As an intrinsically nonlinear device, modelling of this MR fluid based device is a challenging task and makes the design of a suitable control algorithm a cumbersome situation. Aimed at its application in civil structure, the main purpose of this paper is to test and characterise the hysteretic behaviour of MR pin joint. A test scheme is designed to obtain the dynamic performance of MR pin joint in the dominant earthquake frequency range. Some unique phenomena different from those of MR damper are observed through the experimental testing. A computationally-efficient model is proposed by introducing a hyperbolic element to accurately reproduce its dynamic behaviour and to further facilitate the design of a suitable control algorithm. Comprehensive investigations on the model accuracy and dependences of the proposed model on loading condition (frequency and amplitude) and input current level are reported in the last section of this paper.
Li, Y. & Li, J. 2014, 'A Highly-Adjustable Base Isolator Utilizing Magnetorheological Elastomer: Experimental Testing and Modeling', Journal of Vibration and acoustics -Transactions of the ASME, vol. 137.
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This paper presents a recent research advance on the development of a novel adaptive seismic isolation system to be used in seismic protection of civil structures. A highly-adjustable laminated magneto-rheological elastomer (MRE) base isolator was developed and experimental results show that the prototypical MRE base isolator provides amazing increase of lateral stiffness up to1630%. To facilitate the structural control development using such adaptive MRE base isolator, an analytical model was developed to simulate its behaviors. Comparison between the analytical model and experimental data proves the effectiveness of such model in reproducing the behavior of MRE base isolator.
Jiang, X., Li, Y., Li, J., Wang, J. & Yao, J. 2014, 'Piezoelectric energy harvesting from traffic-induced pavement vibrations', Journal of Renewable and Sustainable Energy, vol. 6.
This paper focuses on the development and experimental testing of a potential clean energy source for powering the remote equipment used in transportation infrastructure. Traditional power sources (i.e., power cables and batteries) are excessively expensive or infeasible in this type of application. A compression-based roadway energy harvester has been developed that can be embedded into pavement to scavenge electrical energy from traffic-induced vibrations. The proposed roadway harvester employs a group of piezoelectric harvesting units to convert traffic-induced vibrations into electrical energy, and each single harvesting unit contains three piezoelectric multilayer stacks. According to the linear theory of piezoelasticity, a two-degree-of-freedom electromechanical model of the piezoelectric harvesting unit was developed to characterize its performance in generating electrical energy under external excitations. Experimental testing in the laboratory was conducted to investigate the output power properties of the harvesting unit and shows good agreement with the theoretical analysis. Based on the testing results of the harvesting unit, the capability of the proposed roadway harvester has been theoretically evaluated and demonstrated that it has the ability to generate sufficient energy for driving common electrical equipment used in transportation infrastructure.
Jiang, X., Li, Y., Wang, J. & Li, J. 2014, 'Electromechanical modeling and experimental analysis of a compression-based piezoelectric vibration energy harvester', International Journal of Smart and Nano Materials, vol. 5, no. 3, p. 152.
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Dackermann, U., Skinner, B. & Li, J. 2014, 'Guided wave-based condition assessment of in situ timber utility poles using machine learning algorithms', Structural Health Monitoring, vol. 13, no. 4, pp. 374-388.
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This paper presents a machine-learning-based approach for the structural health monitoring (SHM) of in-situ timber utility poles based on guided wave (GW) propagation. The proposed non-destructive testing method combines a new multi-sensor testing system with advanced statistical signal processing techniques and state-of-the-art machine learning algorithms for the condition assessment of timber utility poles. Currently used pole inspection techniques have critical limitations including the inability to assess the underground section. GW methods, on the other hand, are techniques potentially capable of evaluating non-accessible areas and of detecting internal damage. However, due to the lack of solid understanding on the GW propagation in timber poles, most methods fail to fully interpret wave patterns from field measurements. The proposed method utilises an innovative multi-sensor testing system that captures wave signals along a sensor array and it applies machine learning algorithms to evaluate the soundness of a pole. To validate the new method, it was tested on eight in-situ timber poles. After the testing, the poles were dismembered to determine their actual health states. Various state-of-the-art machine learning algorithms with advanced data pre-processing were applied to classify the poles based on the wave measurements. It was found that using a support vector machine classifier, with the GW signals transformed into autoregressive coefficients, achieved a very promising maximum classification accuracy of 95.73.1% using 10-fold cross validation on multiple training and testing instances. Using leave-one-out cross validation, a classification accuracy of 93.36.0% for bending wave and 85.710.8% for longitudinal wave excitation was achieved.
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, pp. 1-12.
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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.
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, pp. 1-7.
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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.
zhang, J., Xu, Y., Li, J., Xia, Y. & Li, J. 2013, 'Statistical moment-based structural damage detection method in time domain', EARTHQUAKE ENGINEERING AND ENGINEERING VIBRATION, vol. 12, pp. 13-23.
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A novel structural damage detection method with a new damage index, i.e., the statistical moment-based damage detection (SMBDD) method in the frequency domain, has been recently proposed. The aim of this study is to extend the SMBDD method in the frequency domain to the time domain for building structures subjected to non-Gaussian and non-stationary excitations. The applicability and effectiveness of the SMBDD method in the time domainis verified both numerically and experimentally. Shear buildings with various damage scenarios are fi rst numerically investigated in the time domain taking into account the effect of measurement noise. The applicability of the proposed method in the time domain to building structures subjected to non-Gaussian and non-stationary excitations is then experimentally investigated through a series of shaking table tests, in which two three-story shear building models with four damage scenarios aretested. The identifi ed damage locations and severities are then compared with the preset values. The comparative results are found to be satisfactory, and the SMBDD method is shown to be feasible and effective for building structures subjected to non-Gaussian and non-stationary excitations.
Zeng, J., Guo, Y., Li, Y., Zhu, J. & Li, J. 2013, 'Two-dimensional magnetic property measurement for magneto-rheological elastomer', Journal of Applied Physics, vol. 113, pp. 17A919-1-17A919-3.
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Magneto-rheological elastomer (MRE) is a new kind of smart material. Its rheological properties can be altered and controlled in a real time manner when it is applied an external magnetic field. For calculating magnetic properties of MRE material, usually Maxwell-Garnet equation is used to acquire an approximately effective permeability. This equation treats the magnetic property of particles as linear. However, when the applied magnetic field is alternating or rotating, the nonlinearity of magnetic property and magnetic hysteresis cannot be neglected. Hence, the measurement and modelling of the magnetic properties under alternating and rotating magnetic fields are essential to explore new applications of the material. This paper presents the investigation on the magnetic hysteresis properties of MRE material under one-dimensional (1-D) alternating and two-dimensional (2-D) rotating magnetic field excitations. A kind of MRE material, consisting of 70% carbonyl iron particles, 10% silicone oil, and 20% silicone rubber, was used to investigate the magnetic properties. The diameter of carbonyl iron particles is 3+5 lm. The measurement results, such as the relations between magnetic field intensity (H) and magnetic flux density (B) under different magnetic field excitations on the MRE sample, have been obtained and analyzed. These data would be useful for design and analysis of MRE smart structures like MR dampers.
Cheng, S., Li, J. & Zhou, J. 2013, 'Fast Synchronization Of Directionally Coupled Chaotic Systems', Applied Mathematical Modelling, vol. 37, no. 1-2, pp. 127-136.
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This paper studies the fast synchronization of directionally coupled chaotic systems under a chained interaction topology. Firstly, by applying finite-time stability theory, it is shown that all chaotic systems can achieve synchronization in finite time as long as the coupling strength is strong enough. Secondly, it is proved that the settling times are determined by the interaction strength, system parameters and initial conditions of the chaotic systems. Furthermore, it is found that the settling times are mainly dependent on the bounded value and dimension of the coupled chaotic systems when the individual chaotic sub-system is bounded. Finally, illustrative examples and numerical simulations are given to show the correctness of theoretical results
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
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 structur
Lu, Y., Li, J., Ye, L. & Wang, D. 2013, 'Guided waves for damage detection in rebar-reinforced concrete beams', Construction And Building Materials, vol. 47, no. 1, pp. 370-378.
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The propagation properties of ultrasonic waves in rebar-reinforced concrete beams were investigated for the purpose of damage detection. Two types of piezoelectric (PZT) elements were used in experiments in which PZT disks were attached on the surfaces of concrete beams to observe wave propagation in concrete before and after a four-point bending test, while rectangular PZT patches were attached at the exposed ends of the rebar to monitor wave transmission along the rebar with and without simulated corrosion in the form of partial material removal from the rebar. Experimental testing demonstrated that the surface-attached PZT disks were capable of detecting the change in material properties due to the existence of cracking. In consideration of the inevitable discrepancies in different concrete beams due to specimen preparation and sensor installation, principal component analysis based on statistical parameters extracted from wave signals was applied to highlight the difference between benchmark and damaged rebar. The results show the potential of the principal components as damage indices for quantifying integrity conditions of concrete structures.
Li, Y., Li, J., Tian, T. & Li, W. 2013, 'A highly adjustable magnetorheological elastomer base isolator for applications of real-time adaptive control', Smart Materials and Structures, vol. 22, no. 9, pp. 1-18.
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Inspired by its controllable and field-dependent stiffness/damping properties, there has been increasing research and development of magnetorheological elastomer (MRE) for mitigation of unwanted structural or machinery vibrations using MRE isolators or absorbers. Recently, a breakthrough pilot research on the development of a highly innovative prototype adaptive MRE base isolator, with the ability for real-time adaptive control of base isolated structures against various types of earthquakes including near- or far-fault earthquakes, has been reported by the authors. As a further effort to improve the proposed MRE adaptive base isolator and to address some of the shortcomings and challenges, this paper presents systematic investigations on the development of a new highly adjustable MRE base isolator, including experimental testing and characterization of the new isolator. A soft MR elastomer has been designed, fabricated and incorporated in the laminated structure of the new MRE base isolator, which aims to obtain a highly adjustable shear modulus under a medium level of magnetic field. Comprehensive static and dynamic testing was conducted on this new adaptive MRE base isolator to examine its characteristics and evaluate its performance. The experimental results show that this new MRE base isolator can remarkably change the lateral stiffness of the isolator up to 1630% under a medium level of magnetic field. Such highly adjustable MRE base isolator makes the design and implementation of truly real-time adaptive (e.g. semi-active or smart passive) seismic isolation systems become feasible.
Ha, Q.P., Nguyen, M., Li, J. & Kwok, N. 2013, 'Smart Structures With Current-Driven MR Dampers: Modeling and Second-Order Sliding Mode Control', IEEE/ASME Transactions on Mechatronics, vol. 18, no. 6, pp. 1702-1711.
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Smart structures are civil or mechanical structures that can automatically and intelligently react to external dynamic loadings such as vibration shocks, strong winds, destructive waves, and earthquakes. The use of magnetorheological (MR) dampers has been of increasing interest in smart structures as they have reliable, stable and fail-safe operations, small energy requirements, and fast responses. The challenges of MR damper structural control rest with the complex dynamics involved, high nonlinearity due to the force+velocity hysteresis, nonaffinity, and constraints of the control system with the magnetization current as its input. To address these problems, this paper presents the modeling and control design as well as the implementation results of a secondorder sliding mode controller for the MR dampers embedded in the building structures subject to quake-induced vibrations. Based on the static hysteresis model of the MR damper using computationally tractable algebraic expressions, algorithms are proposed to control directly the magnetization current to the dampers, configured in a differential mode to counteract the offset force. The effectiveness of the proposed technique is verified in simulation by using a building model under quake-like excitations. The experimental results are provided on a laboratorial setup tested on a shake table.
Yang, J., Du, H., Li, W., Li, Y., Li, J., Sun, S. & Deng, H. 2013, 'Experimental study and modeling of a novel magnetorheological elastomer isolator', Smart Materials and Structures, vol. 22, no. 11, pp. 1-14.
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This paper reports an experimental setup aiming at evaluating the performance of a newly designed magnetorheological elastomer (MRE) seismic isolator. As a further effort to explore the field-dependent stiffness/damping properties of the MRE isolator, a
Chen, P., Li, J., Wong, L., Kuwahara, H., Huang, J. & Gao, X. 2013, 'Accurate prediction of hot spot residues through physicochemical characteristics of amino acid sequences', Proteins-Structure Function And Bioinformatics, vol. 81, no. 8, pp. 1351-1362.
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Hot spot residues of proteins are fundamental interface residues that help proteins perform their functions. Detecting hot spots by experimental methods is costly and time-consuming. Sequential and structural information has been widely used in the compu
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, vol. 7894, no. 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.
Li, J., Subhani, M. & 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.
Chen, P., Wong, L. & Li, J. 2012, 'Detection Of Outlier Residues For Improving Interface Prediction In Protein Heterocomplexes', Ieee-Acm Transactions On Computational Biology And Bioinformatics, vol. 9, no. 4, pp. 1155-1165.
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Sequence-based understanding and identification of protein binding interfaces is a challenging research topic due to the complexity in protein systems and the imbalanced distribution between interface and noninterface residues. This paper presents an out
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.
Li, Z., He, Y., Wong, L. & Li, J. 2012, 'Progressive Dry-Core-Wet-Rim Hydration Trend In A Nested-Ring Topology Of Protein Binding Interfaces', BMC Bioinformatics, vol. 13, pp. 1-16.
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Background: Water is an integral part of protein complexes. It shapes protein binding sites by filling cavities and it bridges local contacts by hydrogen bonds. However, water molecules are usually not included in protein interface models in the past, an
Huang, Q., Xu, Y.L., Li, J., Su, Z. & Liu, H. 2012, 'Structural Damage Detection Of Controlled Building Structures Using Frequency Response Functions', Journal Of Sound And Vibration, vol. 331, no. 15, pp. 3476-3492.
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If a building structure requires both a vibration control system and a health monitoring system, the integration of the two systems will be cost-effective and beneficial. One of the key problems of this integrated system is how to use control devices to enhance system identification and damage detection. This paper presents a new method for system identification and damage detection of controlled building structures equipped with semi-active friction dampers through model updating based on frequency response functions. The two states of the building are first created by adding a known stiffness using semi-active friction dampers. A scheme based on the frequency response functions of the two states of the building is then presented to identify stiffness parameters of structural members in consideration of structural connectivity and transformation information. By applying the proposed model updating scheme to the damaged building, a damage detection scheme is proposed based on the identified stiffness parameters of structural members of both the original and damaged buildings. The feasibility of the proposed schemes is finally demonstrated through a detailed numerical investigation in terms of an example building, in which the effects of measurement noise and excitation conditions are discussed. The numerical results clearly show that the proposed method can locate and quantify damage satisfactorily even though measurement noise is taken into consideration.
Nguyen, T.V., Ngo, H.H., Guo, W., Phuntsho, S. & Li, J. 2011, 'A New Sponge Tray Bioreactor In Primary Treated Sewage Effluent Treatment', Bioresource Technology, vol. 102, no. 9, pp. 5444-5447.
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The new attached growth sponge tray bioreactor (STB) was evaluated at different operating conditions for removing organics and nutrients from primary treated sewage effluent. This STB was also assessed when using as a pre-treatment prior to micro-filtrat
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.
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.
Qin, Z., Su, G., Zhang, J., Ouyang, Y., Yu, Q. & Li, J. 2010, 'Identification Of Important Factors For Water Vapor Flux And Co2 Exchange In A Cropland', Ecological Modelling, vol. 221, no. 4, pp. 575-581.
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Water vapor flux and carbon dioxide (CO2) exchange in croplands are crucial to water and carbon cycle research as well as to global warming evaluation. In this study, a standard three-layer feed-forward back propagation neural network technique associate
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. & Crews, K.I. 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.
Sun, S., Huang, Z., Zhong, H., Dai, D., Liu, H. & Li, J. 2010, 'Efficient Monitoring Of Skyline Queries Over Distributed Data Streams', Knowledge And Information Systems, vol. 25, no. 3, pp. 575-606.
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Data management and data mining over distributed data streams have received considerable attention within the database community recently.
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.
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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.
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.
Xu, Y., Zhang, J., Li, J. & Xia, Y. 2009, 'Experimental Investigation on Statistical Moment-Based Structural Damage Detection Method', Structural Health Monitoring, vol. 8, no. 6, pp. 555-571.
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Although vibration-based structural damage detection methods have demonstrated various degrees of success, the damage detection of civil structures still remains as a challenging task. The main obstacles include the insensitivity to local damage and the high sensitivity to measurement noise. A new structural damage detection method based on the statistical moments of dynamic responses of a structure has been recently proposed by the authors, and the numerical study manifested that the proposed method is sensitive to local structural damage but insensitive to measurement noise. The experimental investigation on this method is presented in this article. Three shear building models with and without damage were built and subjected to ground motions generated by a shaking table. The displacement and acceleration responses of each building model at each floor were recorded. The recorded ground motion and building responses as well as identified structural damping ratios were then used to identify damage locations and severities using the statistical moment-based damage detection method. The identified damage locations and severities were compared with the theoretical values. The comparison is found satisfactory, and the method proposed is effective and feasible.
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.
Choi, F., Li, J., Samali, B. & Crews, K.I. 2008, 'Application of the Modified Damage Index method to timber beams', Engineering Structures, vol. 30, no. 4, pp. 1124-1145.
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2007, Australia Received 31 August 2006; revised 16 July 2007; Accepted 16 July 2007. Available online 21 August 2007. Abstract 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.
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.
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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 signifi cantly better and has the clear advantage of being simpler to construct, as well as being a viable option for the retrofi t-strengthening of existing dwellings.
Ha, Q.P., Kwok, N., Nguyen, M., 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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As losses of human lives and damages to buildings frequently occur during earthquake periods, it is crucial to mitigate structural vibrations. This paper describes the development of a Lyapunov-based control approach for magnetorheological (MR) dampers i
Samali, B., Dowling, D.M. & Li, J. 2008, 'Static and Dynamic testing of adobe mud-brick structures', Australian Journal of Structural Engineering, vol. 8, no. 2, pp. 159-165.
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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
Choi, F., Li, J., Samali, B. & Crews, K.I. 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 e
Kwok, N., Ha, Q.P., Nguyen, M., Li, J. & Samali, B. 2007, 'Bouc-Wen model parameter identification for a MR 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.
Hong, S., Nguyen, M., Kwok, N., Ha, Q.P. & Li, J. 2007, 'Hysteretic model for magnetorheological fluid dampers using a curve fitting approach', Journal of JSAEM, Japanese Society of Applied Electromagnetics and Mechanics, vol. 15, pp. 176-179.
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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.
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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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.
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Kwok, N., Ha, Q.P., Nguyen, T., 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 BoucWen 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 forcevelocity 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.
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 Heath 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
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.
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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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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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.
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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.
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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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.
Zhang, X., Wang, C.H., Li, J., Mai, Y. & Ye, L. 2000, 'A combined model of short crack closure accounting for both plasticity and proghness induced crack closures', Key Engineering Materials, vol. 0, no. 0, pp. 183-187-217-222.
Taylor, D.A., Li, J. & Giese, A. 1995, 'Short fatigue crack growth in cast iron described using P-a curves', International Journal Of Fatigue, vol. 17, no. 3, pp. 201-206.
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A new approach to the description of short crack growth - the P - a curve - has been tested using extensive data on submillimetre cracks in a grey cast iron. It is shown that this approach, in which the probability of growth is plotted as a function of crack length, is valid in that it produces a plot that is consistent from specimen to specimen and is a function of both crack length and stress level. The growth probability, Pg, can be defined systematically in terms of the average amount of crack growth, ++cmean within a given interval of cycles, ++N; this leads to the concept that Pg characterizes growth at a particular rate: ++cmean/++N. Predictions were made of the endurance, Nf, using a numerical model that simulates the growth of a large number of cracks. Crack coalescence was found to be a critical feature, both of the model and of the experimental findings. The great majority of crack growth was found to occur by coalescence; a simple model of coalescence, based on fracture mechanics, was successfully incorporated into the predictions.
Strugnell, R.A., Dougan, G., Chatfield, S., Charles, I.G., Fairweather, N., Tite, J., Li, J., Beesley, J. & Roberts, M. 1992, 'Characterization Of A Salmonella-Typhimurium-Aro Vaccine Strain Expressing The P.69 Antigen Of Bordetella-Pertussis', Infection And Immunity, vol. 60, no. 10, pp. 3994-4002.
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The P.69 Bordetella pertussis protective antigen was expressed by use of the trc promoter from the chromosome of a Salmonella typhimurium aro vaccine strain, BRD509, by integrating the prn gene, encoding the 93-kDa precursor of this protein, into the aro
Li, J., Fairweather, N., Novotny, P., Dougan, G. & Charles, I.G. 1992, 'Cloning, Nucleotide-Sequence And Heterologous Expression Of The Protective Outer-Membrane Protein P.68 Pertactin From Bordetella-Bronchiseptica', Journal Of General Microbiology, vol. 138, no. NA, pp. 1697-1705.
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The prn gene encoding the 68 kDa protective outer-membrane protein of Bordetella bronchiseptica (P.68 pertactin) was cloned, sequenced and expressed in Escherichia coli. The gene was isolated by DNA: DNA hybridization experiments using a radioactively-la