Jun Li obtained his PHD degree in Structural Engineering from the University of Western Australia, and worked two years in the University of Adelaide before joining the University of Technology Sydney.
Jun Li is now looking for PhD students with background in structural analysis/dynamics. Full scholarship will be provided to the suitable candidates.
Can supervise: YES
- Simulation of blast effects on structures
- Development of ultra-high performance concrete
- Sacrificial metallic foam against blast loads
- Meso-scale model for concrete and steel fibre concrete
- Concrete Design
- Engineering Mechanics
- Structural Analysis
© 2018 Elsevier Ltd. All rights reserved. Development of Ultra-High Performance Concrete against Blasts: From Materials to Structures presents a detailed overview of UHPC development and its related applications in an era of rising terrorism around the world. Chapters present case studies on the novel development of the new generation of UHPC with nano additives. Field blast test results on reinforced concrete columns made with UHPC and UHPC filled double-skin tubes columns are also presented and compiled, as is the residual load-carrying capacities of blast-damaged structural members and the exceptional performance of novel UHPC materials that illustrate its potential in protective structural design. As a notable representative, ultra-high performance concrete (UHPC) has now been widely investigated by government agencies and universities. UHPC inherits many positive aspects of ultra-high strength concrete (UHSC) and is equipped with improved ductility as a result of fiber addition. These features make it an ideal construction material for bridge decks, storage halls, thin-wall shell structures, and other infrastructure because of its protective properties against seismic, impact and blast loads.
Meng, Q, Wu, C, Su, Y, Li, J, Liu, J & Pang, J 2019, 'A study of steel wire mesh reinforced high performance geopolymer concrete slabs under blast loading', Journal of Cleaner Production, vol. 210, pp. 1150-1163.View/Download from: Publisher's site
In this study, a novel green construction material, high performance alkali-activated geopolymer concrete is introduced. Both numerically and experimentally investigations were conducted on a new type of structural slabs made of steel wire mesh reinforced geopolymer concrete against close-in ground surface explosion. Steel rebar reinforced conventional concrete slabs are also studied to compare the results. The experimental investigation was conducted to study the slab damage mechanism. It is found that the steel wire mesh reinforced geopolymer concrete slab showed less damage and fragmentation under 50 kg Trinitrotoluene (TNT) blast load within 3 m, 5 m and 7 m distances as compared to the C30 concrete slab. Numerical analysis was then conducted to further investigate the slab dynamic responses. Combining the steel wire mesh reinforcement with geopolymer concrete can help increase the blast resistance capacity leading to promising and environmental friendly structural protective design.
Liu, J, Wu, C, Li, J, Fang, J, Su, Y & Shao, R 2019, 'Ceramic balls protected ultra-high performance concrete structure against projectile impact-A numerical study', INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, vol. 125, pp. 143-162.View/Download from: Publisher's site
Liu, J, Wu, C, Li, C, Dong, W, Su, Y, Li, J, Cui, N, Zeng, F, Dai, L, Meng, Q & Pang, J 2019, 'Blast testing of high performance geopolymer composite walls reinforced with steel wire mesh and aluminium foam', Construction and Building Materials, vol. 197, pp. 533-547.View/Download from: Publisher's site
© 2018 Elsevier Ltd Two blast tests were conducted to study the blast resistance of high performance geopolymer composite walls reinforced with steel wire mesh (SWM) and aluminium foam (AF). Conventional reinforced concrete (CRC) walls were also tested as control specimens. In total seven walls were tested under different blast loading conditions. The first blast test was conducted on one 2260 mm × 2260 mm × 150 mm SWM reinforced, one 2260 mm × 1000 mm × 150 mm SWM reinforced and one 2260 mm × 1000 mm × 150 mm combined SWM and AF reinforced high performance geopolymer composite walls under 50 kg TNT explosives at a standoff distance of 2.3 m. The second blast test was conducted on one 2260 mm × 2260 mm × 150 mm SWM reinforced and one 2260 mm × 2260 mm × 150 mm combined SWM and AF reinforced high performance geopolymer composite walls under 100 kg TNT explosives on the ground at the same standoff distance. Blast tests were also performed on two 2260 mm × 2260 mm × 150 mm CRC walls under such two designed explosions to compare their behaviours with reinforced high performance geopolymer composite walls. LVDT (linear variable differential transformer) devices were used to record the deflection histories and pressure sensors were used to measure the airblast pressure histories. The testing results indicated that the combined SWM and AF reinforced high performance geopolymer composite walls had a better blast resistance than the CRC walls, and the SWM reinforced high performance geopolymer composite wall was superior to both.
Fang, J, Wu, C, Li, J, Liu, Q, Wu, C, Sun, G & Li, Q 2019, 'Phase field fracture in elasto-plastic solids: Variational formulation for multi-surface plasticity and effects of plastic yield surfaces and hardening', International Journal of Mechanical Sciences, vol. 156, pp. 382-396.View/Download from: Publisher's site
The phase field modelling has been extended from brittle fracture to ductile fracture by incorporating plasticity. However, the effects of plastic yield functions and hardening on the fracture behaviour have not been examined systematically to date. The phase field fracture coupled with multi-surface plasticity is formulated in the variational framework for the unified yield criterion, which is able to facilitate the study on different yield surfaces. First, the homogeneous solutions of fracture in elasto-plastic solids are derived analytically for 1D and 2D cases. The results show that a greater hardening modulus would lead to an ascending branch of the stress versus strain curve; and the yield function may significantly affect the stress state and phase field damage. Second, the finite element (FE) technique is implemented for modelling the phase field fracture in elasto-plastic solids, in which the stress update and consistent tangent modular matrix are derived for the unified yield criterion. Finally, three numerical examples are presented to explore the effects of the yield function and material hardening. It is found that the yield function and material hardening could significantly affect the crack propagation and the final fracture pattern. In particular, the Tresca yield function tends to create a straight crack path orthogonal to the first principal stress, while the other yield functions show no sizeable difference in their crack paths.
Meng, Q, Wu, C, Su, Y, Li, J, Liu, J & Pang, J 2019, 'Experimental and numerical investigation of blast resistant capacity of high performance geopolymer concrete panels', Composites Part B: Engineering.View/Download from: Publisher's site
Li, J, Wu, C & Liu, ZX 2018, 'Comparative evaluation of steel wire mesh, steel fibre and high performance polyethylene fibre reinforced concrete slabs in blast tests', Thin-Walled Structures.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd. Concrete is the most widely used construction material in the modern construction practice. Due to its relatively low tensile resistance, concrete tends to experience tensile failure and cracking under external loads. To enhance the tensile performance and ductility of concrete material, possible solutions including fibre reinforcement and steel mesh reinforcement are investigated in the present study. Steel fibre, ultra-high molecular weight polyethylene (UHMWPE) fibre and steel wire meshes were mixed with varying volume fraction in the concrete matrix. Static material tests including uniaxial compression and flexural bending tests showed that the steel fibre addition yielded better strength enhancement while UHMWPE fibre provided better material ductility. Concrete samples with hybrid steel fibre-steel mesh reinforcement showed high strength and ductility. Field blast tests are designed to study the behaviour of reinforced concrete slabs under close-in detonations. Different damage profiles are observed from the blast tests. The advantages and disadvantages of using different reinforcing materials are discussed. From the results, the advantages of replacing steel fibre with UHMWPE fibre or steel wire mesh were demonstrated.
Liu, J, Wu, C, Li, J, Su, Y & Chen, X 2018, 'Numerical investigation of reactive powder concrete reinforced with steel wire mesh against high-velocity projectile penetration', CONSTRUCTION AND BUILDING MATERIALS, vol. 166, pp. 855-872.View/Download from: UTS OPUS or Publisher's site
Li, J & Wu, C 2018, 'Damage evaluation of ultra-high performance concrete columns after blast loads', International Journal of Protective Structures, vol. 9, no. 1, pp. 44-64.View/Download from: UTS OPUS or Publisher's site
© 2017, © The Author(s) 2017. As emerging advanced construction material, ultra-high performance concretes have seen increasing field applications over the past two decades to take advantages of their ultra-high mechanical strength and durability; yet the systematic study on its dynamic behaviour under impact and blast loads is not commonly seen. This article presents an experimental and numerical study on the static and dynamic behaviour of an existing ultra-high performance concrete material. Experimental study on its flexural behaviour under static loads is conducted and an inverse study is carried out to derive its uniaxial tensile constitutive law. The derived relationship is used in the material model in hydro-code LS-DYNA together with dynamic material properties to study ultra-high performance concrete columns under blast loads. The residual loading capacity of the column is studied and pressure–impulse diagrams for assessing the ultra-high performance concrete column damage under blast loads are proposed. Parametric study on effects of ultra-high performance concrete strength, column height, cross-section size and reinforcement ratio is performed and analytical equations are proposed for generating pressure–impulse diagrams for generic ultra-high performance concrete columns.
Xu, S, Wu, C, Liu, Z & Li, J 2018, 'Numerical study of ultra-high-performance steel fibre-reinforced concrete columns under monotonic push loading', ADVANCES IN STRUCTURAL ENGINEERING, vol. 21, no. 8, pp. 1234-1248.View/Download from: UTS OPUS or Publisher's site
Liu, J, Wu, C, Su, Y, Li, J, Shao, R, Chen, G & Liu, Z 2018, 'Experimental and numerical studies of ultra-high performance concrete targets against high-velocity projectile impacts', Engineering Structures, vol. 173, pp. 166-179.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier Ltd Ultra-high performance concrete (UHPC) which is known for high strength, high toughness, excellent ductility and good energy absorption capacity can be adopted as an ideal material in the impact resistant design of structures. In the present study, impact responses of UHPC targets with 3 vol-% ultra-high molecular weight polyethylene (UHMWPE) fibres and UHPC targets with 3 vol-% steel fibres are experimentally investigated subjected to high-velocity projectile penetration, and plain concrete targets under the same loading scenarios are also tested as control specimens for comparative purpose. In addition, numerical studies are conducted to simulate the projectile penetration process into UHPC targets with the assistance of a computer program LS-DYNA. The numerical results in terms of the depth of penetration (DOP) and crater diameter as well as projectile abrasions and damages are compared with the experimental results. Moreover, DOPs of these two types of UHPC targets obtained from tests are compared with the previously proposed empirical model.
Li, J, Wu, C, Hao, H, Liu, Z & Yang, Y 2018, 'Basalt scale-reinforced aluminium foam under static and dynamic loads', Composite Structures, vol. 203, pp. 599-613.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier Ltd In this paper, mechanical performance and deformation behaviour of basalt scale-reinforced closed-cell aluminium foams are investigated. Quasi-static uniaxial compressive tests on the constitutive alloy material reveal that after basalt scale reinforcement, the alloy elasticity modulus and yield strength show noticeable enhancement. Quasi-static compression tests on the foam material show that while basalt scale-reinforced aluminium foam has higher plastic crush stress and plateau stress, the densification strain is lower than non-reinforced foam. A method based on energy absorption efficiency is adopted to accurately measure the densification strain for both foam materials. In the subsequent split-Hopkinson pressure bar tests, dynamic compressive behaviour of basalt scale-reinforced aluminium foams with relative densities ranged from 14% to 33% is studied experimentally under strain rate ranging from 480/s to 1720/s. Clear material rate sensitivity is noted from the dynamic tests. The results indicate that the plateau stress of aluminium foam increases with relative density and strain rate. In addition, with the increase in strain rates, an increase in the energy absorption capacity is observed and this characteristic is beneficial when the foam material is used to absorb impact energy. A mesoscopic model based on the X-ray CT for the aluminium foam material is developed. The simulations and the test data agreed well for the quasi-static loading case. However, it is noted that the mesoscale model without consideration of the base material rate sensitivity and the entrapped gas underestimated the strength enhancement under dynamic loading scenario.
Wang, W, Wu, C & Li, J 2018, 'Numerical Simulation of Hybrid FRP-Concrete-Steel Double-Skin Tubular Columns under Close-Range Blast Loading', JOURNAL OF COMPOSITES FOR CONSTRUCTION, vol. 22, no. 5.View/Download from: UTS OPUS or Publisher's site
Liu, K, Li, Q, Wu, C, Li, X & Li, J 2018, 'A study of cut blasting for one-step raise excavation based on numerical simulation and field blast tests', International Journal of Rock Mechanics and Mining Sciences, vol. 109, pp. 91-104.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier Ltd Over the past several decades, raise excavation has been widely employed in underground mining, civil engineering and military engineering. One-step raise excavation with burn cuts, where all the boreholes are pre-drilled and detonated at one time and no workers need to be underneath the freshly blasted and dangerous ground, is an important and promising method in raise excavation. Cut parameters, especially the parameters of prime cut which used empty hole as a free surface and swelling space, have significant influence on the effect of raise formed. In this study, two small-scale experimental methods, spiral hole spacing method and observation hole method, are designed to determine the prime cut parameters such as hole spacing (L), stemming length (Ls1, Ls2) and air deck length (La) which are normally determined by empirical formula. In order to study the feasibility of the two methods, numerical analysis and experimental tests are conducted in V zone of Sandaozhuang molybdenum mine (SMM), in which there are large numbers of underground goafs need to be controlled by filled raise. The Riedel–Hiermaier–Thoma (RHT) material model, which considers compression damage and tension damage effect under blasting loading, is employed in the LS-DYNA software to study the rock damage zone. Meanwhile, the field tests are carried out according to the two small-scale experimental methods. The comparison results show that the damage zone of numerical simulation has a good agreement with the experimental data. Further, the optimal prime cut parameters obtained from experimental tests are applied in one-step filled-raise excavation, and a 23 m raise that meets the design requirements is formed through the proposed technology. The results indicate that these cut parameters determined by the small-scale experiments are suited for one-step raise excavation. This study can provide two simple field experiments to determine the important prime cut parameters of one...
Xu, J, Wu, C, Li, J & Cui, J 2017, 'Simplified finite element method analysis of ultra-high-performance fibre-reinforced concrete columns under blast loads', Advances in Structural Engineering, vol. 20, no. 1, pp. 139-151.View/Download from: UTS OPUS or Publisher's site
Ultra-high-performance fibre-reinforced concrete has exceptional mechanical properties including high compressive and tensile
strength as well as high fracture energy. It has been proved to be much higher blast resistant than normal concrete. In this article, flexural
behaviours of ultra-high-performance fibre-reinforced concrete columns were investigated through full-scale tests. Two 200 mm
3 200 mm 3 2500 mm columns with and without axial loading were investigated under three-point bending tests, and their load–
displacement relationships were recorded and the moment curvatures were derived. The derived moment curvature relationships of
ultra-high-performance fibre-reinforced concrete columns were then incorporated into a computationally efficient one-dimensional
finite element model, which utilized Timoshenko beam theory, to determine flexural response of ultra-high-performance fibrereinforced
concrete columns under blast loading. After that, the one-dimensional finite element model was validated with the real
blast testing data. The results show good correlation between the advanced finite element model and experimental results. The feasibility
of utilizing the one-dimensional finite element model for simulating both high-strength reinforced concrete and ultra-highperformance
fibre-reinforced concrete columns against blast loading conditions is confirmed
Li, J, Wu, C, Hao, H & Su, Y 2017, 'Experimental and numerical study on steel wire mesh reinforced concrete slab under contact explosion', MATERIALS & DESIGN, vol. 116, pp. 77-91.View/Download from: UTS OPUS or Publisher's site
Su, Y, Li, J, Wu, C, Wu, P, Tao, M & Li, X 2017, 'Mesoscale study of steel fibre-reinforced ultra-high performance concrete under static and dynamic loads', Materials and Design, vol. 116, pp. 340-351.View/Download from: UTS OPUS or Publisher's site
© 2016 Elsevier Ltd In this paper, a three-dimensional numerical model to study the static and dynamic behaviour of ultra-high performance steel fibre reinforced concrete is developed. Ultra-high performance steel fibre reinforced concrete is assumed to be a two-phase model consisting of concrete matrix and steel fibres. The concrete matrix is modelled with homogeneous material and the straight round steel fibres are assumed to be dispersed with random locations and orientations in the matrix. The interfacial transition zone (ITZ) effect is studied based on the single fibre pull-out tests, and parameters describing the fibre-matrix one dimensional bond-slip behaviour are obtained and discussed based on both experimental and theoretical results. After the three-dimensional model is validated with static split tensile tests, split Hopkinson pressure bar (SHPB) split tensile tests are numerically modelled and the stress-time history is interpreted in the mesoscale level. The proposed model qualitatively and quantitatively predicts the material static and dynamic behaviours, and also gives insights on the fibre reinforcement effect in the concrete matrix.
Wang, H, Wu, C, Zhang, F, Fang, Q, Xiang, H, Li, P, Li, Z, Zhou, Y, Zhang, Y & Li, J 2017, 'Experimental study of large-sized concrete filled steel tube columns under blast load', Construction and Building Materials, vol. 134, pp. 131-141.View/Download from: UTS OPUS or Publisher's site
© 2016 This paper investigates blast resistance and residual strength of concrete-filled steel tube (CFST) columns under close-range blast loads. A total of 8 CFST columns, including 4 with circular cross sections and 4 with square cross sections, were tested under close-range blasts. LVDTs were used to record displacement histories and pressure sensors were used to measure pressure histories. The influence of explosive charge weight, steel tube thickness and cross section geometry on dynamic response of CFST columns was analyzed and failure modes of CFST columns were also investigated. Following the blast tests, an experimental study was conducted to investigate residual strength of blast-damaged CFST columns. It was found that the CFST columns were still able to retain a large portion of their axial load capacities even after close-range blast events.
Su, Y, Wu, C, Li, J, Li, Z-X & Li, W 2017, 'Development of novel ultra-high performance concrete: From material to structure', CONSTRUCTION AND BUILDING MATERIALS, vol. 135, pp. 517-528.View/Download from: UTS OPUS or Publisher's site
© 2016 Elsevier Ltd Over the past several decades, iconic and public buildings have become targets of terrorist bomb attacks, but most of these buildings were built without consideration of blast loading scenarios. Key load-carrying elements such as concrete columns are probably the most critical structural components for structural protection against bomb threats. Failures of columns may trigger catastrophic progressive collapse if there is insufficient structural redundancy. In a recent study, novel ultra-high performance concrete (UHPC) material formulated based on reactive powder concrete (RPC) was developed. Field blast tests on columns made of this material were performed. Test results showed that UHPC columns had excellent blast resistant capability, only small mid-height deflection and minor concrete damage was observed after the blasting tests. In the present study, to quantify blast-induced damage and assess residual loading capacity of UHPC columns, static axial loading tests on post-blast UHPC columns were carried out. Undamaged control samples were tested to provide benchmarks. Damage index and residual loading capacity of UHPC columns after various blast loadings were obtained. It was found that column cast with micro steel fibre reinforced UHPC preserved more than 70% of its loading capacity after 35 kg TNT detonation at 1.5 m standoff distance, while high strength concrete column only maintained 40% loading capacity after 8 kg TNT detonation at 1.5 m standoff distance.
Li, J, Wu, C, Hao, H, Su, Y & Li, ZX 2017, 'A study of concrete slabs with steel wire mesh reinforcement under close-in explosive loads', International Journal of Impact Engineering, vol. 110, pp. 242-254.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd.Structural responses and damages under blast loading environments are critical to structural and personnel safety. The blast scenarios involving close-in detonations are attracting increasingly more attentions over the last few decades due to the rising of terrorism. Under close-in detonations, structural elements tend to fail in a brittle mode including shear, concrete crater and spall. In such loading scenarios, the structural designated loading capacity which is usually based on flexural deformation assumption is not fully developed. To provide high-level structural protection, high performance concretes with varying fibre additions are now widely investigated and used in blast resistance designs. In the present study, field blast tests results on reinforced concrete slabs under close-in detonations are presented. Performances of slabs made of normal strength concrete and steel fibre reinforced concrete are compared and discussed. Besides conventional steel rebar reinforcement, new reinforcement scheme i.e. hybrid steel wire mesh-micro steel fibre reinforcement is investigated through the laboratory static tests and field blast tests. Furthermore, a numerical study based on Multi-Material ALE and Lagrangian algorithm is carried out to further investigate the field tests' phenomenon.
Wu, C & Li, J 2017, 'Structural Protective Design with Innovative Concrete Material and Retrofitting Technology', Procedia Engineering, vol. 173, pp. 49-56.View/Download from: UTS OPUS or Publisher's site
© 2017 The Authors. Retrofitting technology and high performance construction material are now widely investigated so as to increase structural ductility and robustness under extreme loading conditions. In the present study, some recent developments in structural protection against blast loads are compiled. Metallic foam materials with varying foam density and gradient are used in the cladding design, their energy absorbing capacities and stress-strain relationships are studied based on uniaxial compression tests. These foam material are used to cast sacrificial claddings on the concrete slabs in the field blast tests. Damage and structural deformation are measured to check the effectiveness of the claddings. Besides sacrificial foam cladding, concrete material with new reinforcement scheme including steel wire mesh and micro steel fiber is developed, and the static test results indicates the excellent ductility and crack control ability of this novel design. In the field blast tests, concrete slabs with different steel wire mesh reinforcement are exposed to varying blast loads. The effectiveness of the slab reinforcing design is discussed based on field performance.
Liu, J, Wu, C, Li, J, Su, Y, Shao, R, Liu, Z & Chen, G 2017, 'Experimental and numerical study of reactive powder concrete reinforced with steel wire mesh against projectile penetration', International Journal of Impact Engineering, vol. 109, pp. 131-149.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd This paper presents experimental and numerical studies on impact resistance of reactive powder concrete (RPC) targets reinforced with 44-layer steel wire meshes. Steel ogive-nosed projectiles with an average mass of 330 g and striking velocities ranging from 550 m/s to 800 m/s were launched against the cylindrical RPC targets with 750 mm diameter and 700 mm thickness. The impact responses observed in the tests, including depth of penetration (DOP), crater diameter and volume loss, were investigated and discussed, which indicates an effective impact resistance of steel wire mesh reinforced RPC in comparison with the previous studies on ultra-high performance based cement composites (UHPCC) with additions of fibres and basalt aggregates. Numerical studies based on validated material and element models are also conducted to simulate the impact responses of reinforced RPC targets against high-velocity proj ectile penetration in explicit hydro-code LS-DYNA. The impact responses, especially for the DOP, are well predicted by using the numerical models. Moreover, further investigation based on the verified numerical models is discussed in the present paper to explore the influence of mechanical and physical properties of steel wire mesh reinforcement on the resistance of projectile penetration.
Yuan, S, Hao, H, Zong, Z & Li, J 2017, 'A study of RC bridge columns under contact explosion', INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, vol. 109, pp. 378-390.View/Download from: UTS OPUS or Publisher's site
Hao, H, Hao, Y, Li, J & Chen, W 2016, 'Review of the current practices in blast-resistant analysis and design of concrete structures', ADVANCES IN STRUCTURAL ENGINEERING, vol. 19, no. 8, pp. 1193-1223.View/Download from: UTS OPUS or Publisher's site
Su, Y, Li, J, Wu, C, Wu, P & Li, Z-X 2016, 'Influences of nano-particles on dynamic strength of ultra-high performance concrete', COMPOSITES PART B-ENGINEERING, vol. 91, pp. 595-609.View/Download from: Publisher's site
Li, J, Wu, C, Hao, H, Su, Y & Liu, Z 2016, 'Blast resistance of concrete slab reinforced with high performance fibre material', Journal of Structural Integrity and Maintenance, vol. 1, no. 2, pp. 51-59.View/Download from: UTS OPUS or Publisher's site
Li, J, Wu, C, Hao, H, Wang, Z & Su, Y 2016, 'Experimental investigation of ultra-high performance concrete slabs under contact explosions', INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, vol. 93, pp. 62-75.View/Download from: UTS OPUS or Publisher's site
Xu, J, Wu, C, Xiang, H, Su, Y, Li, Z-X, Fang, Q, Hao, H, Liu, Z, Zhang, Y & Li, J 2016, 'Behaviour of ultra high performance fibre reinforced concrete columns subjected to blast loading', ENGINEERING STRUCTURES, vol. 118, pp. 97-107.View/Download from: Publisher's site
Li, J, Wu, C & Hao, H 2015, 'Residual loading capacity of ultra-high performance concrete columns after blast loads', International Journal of Protective Structures, vol. 6, no. 4, pp. 649-669.View/Download from: UTS OPUS or Publisher's site
Columns are essential load carrying structural components and may experience accidental loads such as terrorist bombing attacks during their service life. Damages to columns may trigger structural collapse and it is therefore very important to protect critical load-carrying columns. In recent studies, a novel ultra-high performance concrete (UHPC) material was developed and static loading test results revealed its outstanding mechanical strengths and ductility. The present study investigates the blast load-carrying capacities of columns made of UHPC. Concrete columns built with UHPC were blast tested in the field first; then brought back to laboratory and subjected to static load tests to determine their residual load-carrying capacities after experiencing varying levels of blast damage. The results from the field blast tests and laboratory static load tests for residual load-carrying capacities are presented and discussed in this paper. Numerical models for simulating responses and residual strengths of the UHPC columns after blast loadings are also developed in commercial hydro-code LS-DYNA and presented in the paper. Comparisons between the test data and numerical results are made and the accuracy of the numerical model is validated.
Li, J, Wu, C & Hao, H 2015, 'An experimental and numerical study of reinforced ultra-high performance concrete slabs under blast loads', MATERIALS & DESIGN, vol. 82, pp. 64-76.View/Download from: UTS OPUS or Publisher's site
Li, J, Wu, C, Hao, H & Su, Y 2015, 'Investigation of ultra-high performance concrete under static and blast loads', International Journal of Protective Structures, vol. 6, no. 2, pp. 217-234.View/Download from: UTS OPUS or Publisher's site
Conventional concrete works as an important construction material. However, conventional concrete is known to be brittle and prone to tensile failure and cracks. To overcome such defects and improve the dynamic performance of concrete against extreme loading conditions, concrete with different additions and formulae have been developed. In a recent study, to develop ultra-high performance concrete (UHPC) material with better strength and crack control ability, super fine aggregates with high pozzolanic effect were mixed into the steel fibre reinforced concrete instead of the traditional graded coarse aggregates. Furthermore, to achieve high early age strength, nanoscale additives which can accelerate the hydration process of the ordinary Portland cement were also introduced into the concrete composite. A series of uniaxial compression and four-point bending tests had been performed in the laboratory to get the material properties of this innovative concrete material. Great improvement of the concrete uniaxial compressive strength and flexural tensile strength was observed. Field blast tests were carried out on columns made of this UHPC material. Superior blast resistance performance was observed. In the current study, based on the available test data, numerical models are developed and numerical simulations are carried out. The simulation results are found to comply well with the experimental results.
Li, J, Wu, C & Hao, H 2015, 'Investigation of ultra-high performance concrete slab and normal strength concrete slab under contact explosion', ENGINEERING STRUCTURES, vol. 102, pp. 395-408.View/Download from: UTS OPUS or Publisher's site
Li, J & Hao, H 2014, 'A simplified numerical method for blast induced structural response analysis', International Journal of Protective Structures, vol. 5, no. 3, pp. 323-348.View/Download from: UTS OPUS or Publisher's site
Efficiently and accurately predicting structural dynamic response and damage to external blast loading is a big challenge to both structural engineers and researchers. The conventional numerical treatment to this problem is proved being able to give reliable predictions, however at the cost of enormous computational time and resource. Simplified SDOF approach is popularly used in design as it is straightforward to use and also gives good structural response predictions if the response is governed by a global response mode (shear or bending) and the accurate dynamic deflection curve is available, but it cannot predict the detailed local structural damage. In this study, a new numerical approach that combines the recently proposed two-step method and the static condensation method is proposed to analyze structure response and collapse to blast loads. The two-step method divides the structural response into two phases, i.e. forced vibration phase (blast loading duration) and free vibration phase. Single-Degree-of-Freedom system approach is adopted to solve the structural element responses at the end of the forced vibration phase, and the structural free vibration simulation is carried out using the hydro-code LS-DYNA to calculate the detailed structural response and damage. The static condensation technique is utilized to condense structural components that are relatively away from the explosion center to further reduce the computational effort. To demonstrate the proposed method, the structural responses of a three story RC frame to blast loads are calculated by four approaches, i.e. the traditional detailed FE simulation, the two-step method, the model condensation method, and the new combined two-step and dynamic condensation method. Through the results comparison, the efficiency and accuracy of the proposed combined approach are demonstrated.
Li, J & Hao, H 2014, 'Numerical and theoretical study of concrete spall damage under blast loads', Applied Mechanics and Materials, vol. 553, pp. 774-779.View/Download from: UTS OPUS or Publisher's site
Spall damage is a typical failure mode of concrete structures under blast or high velocity impact loads. At the opposite side from which the structural element was impulsively loaded, spall will occur if the net primary stresses over an area exceed the dynamic tensile strength of concrete. Fragments of structural element could eject with large velocities, and this kind of damage can cause severe threats to equipment and personnel. In the present study, reinforced concrete columns subjected to the blast loading is investigated and the numerical study of concrete spall is conducted. The spall depth is recorded and compared with the theoretical results derived from wave propagation theory. The parameters that affect the concrete spall damage are investigated. © (2014) Trans Tech Publications, Switzerland.
Li, J & Hao, H 2013, 'Influence of brittle shear damage on accuracy of the two-step method in prediction of structural response to blast loads', INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, vol. 54, pp. 217-231.View/Download from: UTS OPUS or Publisher's site
Li, J & Hao, H 2011, 'A two-step numerical method for efficient analysis of structural response to blast load', International Journal of Protective Structures, vol. 2, no. 1, pp. 103-126.View/Download from: UTS OPUS or Publisher's site
Even with modern computer power, detailed numerical modeling and simulation of structure response to blast loads are still extremely expensive and sometimes prohibitive because it is very time consuming and requires huge computer memory. Often compromise has to be made between simulation efficiency and simulation accuracy. A lot of research efforts have been spent on improving the computational efficiency. Most of these researches concentrate on simplifying the structures, such as simplifying a structure to an equivalent SDOF system, use smeared reinforcement steel and concrete model, use substructure approach to only model part of the structure in detail. Although these approaches under certain conditions yield reliable predictions, each of them has its associated limitations. Recently a two-step method was developed to improve the computation and modeling efficiency of structure response to blast loads. Instead of simplifying the structure, the proposed method calculates the structural responses in two steps. The first step calculates the structural responses in the loading phase and the second calculates the free vibration responses with the velocity profile of the structure at the end of the loading phase as initial conditions. Using a reinforced concrete beam as the example, it was found that the proposed method yields reliable predictions of the overall beam deflection and stress in longitudinal reinforcement bars with less than 10% computational time as compared to a detailed FE model simulation. However, the predicted stress in hoop reinforcements near the beam supports is not as good. In this paper, the method is improved by also including displacement response at the end of the forced-vibration phase as the initial conditions in the free vibration analysis. The same reinforced concrete beam is used. The results show that including the displacement initial conditions in the two-step method leads to an improved prediction of the beam responses. Parametric...
Li, J & Hao, H 2011, 'Development of a simplified numerical method for structural response analysis to blast load', Procedia Engineering, vol. 14, pp. 2558-2566.View/Download from: UTS OPUS or Publisher's site
The response of structural concrete elements under extremely short duration dynamic loads is of great concern nowadays. The most prevailing method to this problem is based on SDOF simplification. It is well known that the SDOF model can reliably predict the overall structural component response if the response follows predominantly a predefined damage mode such as shear or flexural mode. However, it cannot reliably predict localized failure of structures. Moreover, reliable deflection shape and damage criterion, which are critical for developing the equivalent SDOF model, are difficult to define. Therefore, although most design and analysis are still based on SDOF approach, more and more analyses are conducted with detailed Finite Element (FE) modelling. However, due to the short time duration as well as the huge loading magnitude, it is extremely difficult and time consuming to perform FE structural response analysis to blast loads, even with modern computer power. In this paper, a numerical approach, which substantially reduces the modelling and computational effort in analysing structural responses to blast load, is presented. Based on the short duration of blast load, the structural response is divided into two parts: forced vibration phase and free vibration phase. In the proposed method, the response during the forced vibration phase is approximately solved using the SDOF approach. Using the estimated response quantities at the end of the forced vibration phase as the initial conditions, a detail FE model in LS-DYNA is established and free vibration response is solved. This approach, while yielding reasonably accurate response calculations, substantially reduces the modelling and computational effort. To demonstrate the method, a reinforced concrete beam is analysed using both the conventional detailed FE modelling and the proposed approach. Comparisons of the numerical results from the two methods demonstrate the reliability of the proposed method. Compare...
Li, J & Wu, C 2018, 'Experimental study on ultra-high performance concrete columns against low-velocity impact', Proceedings of the 25th Australasian Conference on Mechanics of Structures and Materials, 25th Australasian Conference on the Mechanics of Structures and Materials, Brisbane.
Li, J & Wu, C 2018, 'Experimental and numerical study on Basalt scale aluminium foam', 7th International Conference on Protection of Structures against Hazards, Hanoi.
Li, J & Wu, CQ 2016, 'Experimental study on steel wire mesh reinforced concrete slabs against close-in detonations', Mechanics of Structures and Materials: Advancements and Challenges - Proceedings of the 24th Australasian Conference on the Mechanics of Structures and Materials, ACMSM24 2016, Australian Conference on the Mechanics of Structures and Materials, CRC Press, Perth, Australia, pp. 567-570.View/Download from: UTS OPUS
© 2017 Taylor & Francis Group, London. High performance and aesthetic appearance of a structural design is the motivation behind high strength concrete development. As a notable representative, high performance steel fibre reinforced concrete is characterized by a much higher compressive and tensile strength compared with conventional concrete, the low water-cement ratio effectively warrants a low porosity microstructure which in turn enhances its durability. In recent years, with threat from terrorism activities, protection of structures against malicious loads such like explosive detonation is attracting more public concern. Due to its excellent mechanical performance and energy absorption capacity, high performance steel fibre reinforced concrete can be used in the construction of key load-carrying components to mitigate the blast induced structural damage. In current study, slabs made of high strength concrete material are field tested under close-in detonations, different reinforcement schemes including steel fibre reinforcement and steel wire mesh reinforcement are used in the slab design. Comparisons are made with normal strength concrete slab. Brief discussion on the different slab design against blast loads are presented.
Wu, C & Li, J 2016, 'Structural protective design with innovative concrete material and retrofitting technology', 11th International Symposium on Plasticity and Impact Mechanics, New Delhi.View/Download from: UTS OPUS
Li, J & Wu, C 2017, 'Fibre-reinforced strain hardening concrete under static and blast loads', 15th East Asia-Pacific Conference on Structural Engineering and Construction, Xi'an.
Li, J, Wu, C & Hao, H 2016, 'Spallation of reinforced concrete slabs under contact explosion', Proceedings of the 2016 2nd Asian Conference on Defence Technology, ACDT 2016, Asian Conference on Defence Technology, IEEE, Changmai, Thailand, pp. 42-45.View/Download from: UTS OPUS or Publisher's site
© 2016 IEEE.Structures and their occupants are imposed to great threat under blast loading environment. The current design and research practices mainly focus on structural responses and damages under far field or close-in detonations. The blast scenarios involving contact explosions are not extensively investigated. Under contact explosions, highly localized damage caused by severe stress wave propagation is commonly seen, and this damage mode is significantly different from other dynamic loading types in which structural members usually respond in flexural or shear mode. In recent decades, the necessity of gaining in-depth knowledge about this extreme loading event is highlighted as threat from terrorism activities is rising. In the present study, contact test results on reinforced concrete members are presented. Performances of slabs made of normal strength concrete and steel wire mesh reinforced concrete are compared and discussed.
Li, J, Wu, C & Hao, H 2016, 'Post-Blast Residual Loading Capacity of Ultra-High Performance Concrete Columns', Proceedings of the First International Interactive Symposium on UHPC, First International Interactive Symposium on UHPC, Iowa State University.View/Download from: Publisher's site
Li, J, Wu, C & Hao, H 2016, 'Experimental and numerical study of a new composite slab under blast loads', 4th International Conference on Protective Structures, Tianjin Chengjian University & Tianjin University, China, Beijing.
Yuan, S, Hao, H, Zong, Z & Li, J 2016, 'Numerical Study of Dynamic Responses of Highway Bridge Piers with Different Sections subjected to Blast Loads', 14th East Asia-Pacific Conference on Structural Engineering and Construction, Ho Chi Minh city.
Li, J, Wu, C & Hao, H 2015, 'Concrete spall damage of UHPC slabs under contact detonation - An experimental investigation', Proceedings of the Second International Conference on Performance-based and Life-cycle Structural Engineering (PLSE 2015), International Conference on Performance-based and Life-cycle Structural Engineering, School of Civil Engineering, The University of Queensland.View/Download from: Publisher's site
Su, Y, Li, J & Wu, C 2015, 'SHPB Test on UHPC with Steel Fibre Reinforcement', 3rd International Conference of Protective Structures, Newcastle.
Su, Y, Li, J, Wu, C, Wu, P & Liu, Z 2015, 'Dynamic Behaviour of UHPC Mixed with Nano Material', Fifth International Conference on Design and Analysis of Protective Structures, Singapore.
Hao, H & Li, J 2014, 'Simplified numeircal method for analysing blast induced structural responses', 2014 SEM FALL Conference & International Symposium on Intensive Loading and Its Effects, Trans Tech Publications Ltd, Beijing.
Li, J, Hao, H & Wu, C 2015, 'Preliminary Investigation of Blast Resistance Capacity of Segmented Column Using Numerical Method', Proceedings of the 3rd International Conference on Protective Structures (ICPS3), Newcastle, Australia, 3-6 February 2015, 3rd International Conference on Protective Structures, Centre for Infrastructure Performance and Reliability, University of Newcastle, Newcastle.
Li, J, Wu, C & Hao, H 2015, 'Blast Resistance of Newly Developed Ultra-High Performance Concrete Columns', Proceedings of the 3rd International Conference on Protective Structures (ICPS3), Newcastle, Australia, 3-6 February 2015, 3rd International Conference on Protective Structures, Newcastle.
Li, J, Wu, C & Hao, H 2015, 'Blast resistance of UHPC slabs-an experimental and numerical study', Proceedings of the 11th International Conference on Shock & Impact Loads on Structures, 11th International Conference on Shock & Impact Loads on Structures, CI-Premier Pte Ltd, Ottawa.
Li, J, Wu, C, Hao, H & Su, Y 2014, 'Numerical analysis of uniaxial compression and four bending tests of ultra-high preformance reinforced concrete', 6th International Conference on Protection of Structures against Hazards, Tianjin.
Xu, J, Wu, C, Xiang, H, Su, Y, Li, Z-X, Fang, Q, Hao, H, Liu, Z, Zhang, Y & Li, J 2014, 'Experimental study on the response of ultra-high preformance reinforced concrete columns under blast loading', 6th International Conference on Protection of Structures against Hazards, Tianjin.
Li, J & Hao, H 2012, 'Influence of brittle shear damage on two-step method prediction of structural response to blast loads', 5th International Conference on Protection of Structures Against Hazards, Singapore :CI-Premier Pte Ltd,2012, Singapore.
Contains various papers presented at the Fifth International Conference on Protection of Structures Against Hazards. The conference was organised to inform and to educate scientists, engineers and the public at large as well, about the causes and consequences of tsunami, earthquakes and radiation exposure.
Li, J & Hao, H 2012, 'Numerical simulation of blast induced structural response using static condensation method', 5th International Conference on Protection of Structures Against Hazards, CI-Premier Pte Ltd, Singapore.
Contains various papers presented at the Fifth International Conference on Protection of Structures Against Hazards. The conference was organised to inform and to educate scientists, engineers and the public at large as well, about the causes and consequences of tsunami, earthquakes and radiation exposure.