Numerical simulation and validation of impact response of axially-restrained steel–concrete–steel sandwich panels

Steel–concrete–steel (SCS) sandwich panels are an effective means for protecting personnel and infrastructure facilities from the effects of external blast and high-speed vehicle impact. In conventional SCS construction, the external steel plates are connected to the concrete infill by welded shear stud connectors. This paper describes a programme of research in which the non-composite SCS panels with axially restrained connections were studied experimentally and numerically. High fidelity finite element models for axially restrained steel–concrete–steel panels subjected to impact loading conditions were developed using LS-DYNA. The simulation results were validated against the dynamic testing experimental results. The numerical models were able to predict the initial flexural response of the panels followed by the tensile membrane resistance at large deformation. It was found that the strain rate effects of the materials and the concrete material model could have significant effect on the numerically predicted flexural strength and tensile membrane resistance of the panels.     

Composite and non-composite behaviors of foam-insulated concrete sandwich panels

The structural behaviors of foam-insulated concrete sandwich panels subjected to uniform pressure have been evaluated. This study showed that the interface conditions such as composite and non-composite had a significant effect on the response of foam-insulated concrete sandwich panels, indicating that the simulated shear tie resistance should indeed be incorporated in numerical analyses. Finite element models were developed to simulate the detailed shear resistance of connectors and the nonlinear behaviors of concrete, foam and rebar components. The models were then validated using data from static tests performed at the University of Missouri. The modeling approach used here was compatible with the American Concrete Institute (ACI) Code and existing design practices. The results of this study will therefore provide improved methodology for the analysis and design of foam-insulated sandwich panels under both static and blast loadings.     

Behaviour of sandwich panels subject to intense air blasts – Part 2: Numerical simulation

Finite element simulation is employed to analyse the behaviour of clamped sandwich panels comprising equal thicknesses mild steel plates sandwiching an aluminium honeycomb core when subject to blast loadings. Pressure-time histories representative of blast loadings are applied to the front plate of the sandwich panel. The FE model is verified using the experimental test results for uniform and localised blast loading in the presence of a honeycomb core and with only an air gap between the sandwich plates. It is observed that for the particular core material, the load transfer to the back plate of the panel depends on the load intensity, core thickness and flexibility of the sandwich panels.     

Modelling the structural response of GLARE panels to blast load

This paper deals with the structural response of fully-clamped quadrangular GLARE panels subjected to an intense air-blast load using the commercial finite element software, LS-DYNA. A cohesive tie-break algorithm is implemented to model interfacial debonding between adjacent plies. The blast loads was simulated using a ConWep blast algorithm and a multi-material ALE formulation with fluid–structure interaction to determine the performance of each method. Numerical model validation have been performed considering case studies of GLARE panels subjected to spherical explosive charges of C-4, for which experimental data on the back face-displacement and post-damage observations were available. Excellent agreement of mid-point deflections and evidence of severe yield line deformation were presented and discussed against the performed blast tests.     

钢纤维高强混凝土抗爆炸研究

对纤维体积率(Vf)为0%―3%、基体强度为C100的钢纤维高强混凝土(SFRHSC)板进行模型爆炸试验,结果表明:爆炸应力波在混凝土中呈现明显的衰减特性,衰减幅度与混凝土强度等级、Vf之间的关系不大,但背爆面加速度峰值和迎爆面破坏程度则随着Vf的增加而降低;SFRHSC最大最显著的优势是抗震塌,在普通混凝土板大面积震塌,碎裂块爆飞的装药量爆炸条件下,SFRHSC板却无震塌发生或只有小块体脱离,裂而不散,其抗震塌性能的提高主要取决于材料的抗拉强度;根据试验结果建立了基于神经网络系统的SFRHSC震塌模型,模型计算的理论值与实测值比较接近。     

Modelling the structural response of GLARE panels to blast load

This paper deals with the structural response of fully-clamped quadrangular GLARE panels subjected to an intense air-blast load using the commercial finite element software, LS-DYNA. A cohesive tie-break algorithm is implemented to model interfacial debonding between adjacent plies. The blast loads was simulated using a ConWep blast algorithm and a multi-material ALE formulation with fluid–structure interaction to determine the performance of each method. Numerical model validation have been performed considering case studies of GLARE panels subjected to spherical explosive charges of C-4, for which experimental data on the back face-displacement and post-damage observations were available. Excellent agreement of mid-point deflections and evidence of severe yield line deformation were presented and discussed against the performed blast tests.     

Blast loading response of reinforced concrete panels reinforced with externally bonded GFRP laminates

The behavior of reinforced concrete panels, or slabs, retrofitted with glass fiber reinforced polymer (GFRP) composite, and subjected to blast load is investigated. Eight 1000 × 1000 × 70 mm panels were made of 40 MPa concrete and reinforced with top and bottom steel meshes. Five of the panels were used as control while the remaining four were retrofitted with adhesively bonded 500 mm wide GFRP laminate strips on both faces, one in each direction parallel to the panel edges. The panels were subjected to blast loads generated by the detonation of either 22.4 kg or 33.4 kg ANFO explosive charge located at a 3-m standoff. Blast wave characteristics, including incident and reflected pressures and impulses, as well as panel central deflection and strain in steel and on concrete/FRP surfaces were measured. The post-blast damage and mode of failure of each panel was observed, and those panels that were not completely damaged by the blast were subsequently statically tested to find their residual strength. It was determined that overall the GFRP retrofitted panels performed better than the companion control panels while one retrofitted panel experienced severe damage and could not be tested statically after the blast. The latter finding is consistent with previous reports which have shown that at relatively close range the blast pressure due to nominally similar charges and standoff distance can vary significantly, thus producing different levels of damage.     

Mechanical response of metallic honeycomb sandwich panel structures to high-intensity dynamic loading

Explosive tests were performed in air to study the dynamic mechanical response of square honeycomb core sandwich panels made from a super-austenitic stainless steel alloy. Tests were conducted at three levels of impulse load on the sandwich panels and solid plates with the same areal density. Impulse was varied by changing the charge weight of the explosive at a constant standoff distance. At the lowest intensity load, significant front face bending and progressive cell wall buckling were observed at the center of the panel closest to the explosion source. Cell wall buckling and core densification increased as the impulse increased. An air blast simulation code was used to determine the blast loads at the front surfaces of the test panels, and these were used as inputs to finite element calculations of the dynamic response of the sandwich structure. Very good agreement was observed between the finite element model predictions of the sandwich panel front and back face displacements and the experimental observations. The model also captured many of the phenomenological details of the core deformation behavior. The honeycomb sandwich panels suffered significantly smaller back face deflections than solid plates of identical mass even though their design was far from optimal for such an application.     

Finite element analysis of sandwich panels with stepwise graded aluminum honeycomb cores under blast loading

This paper presents details and brief results of an experimental investigation on the response of metallic sandwich panels with stepwise graded aluminum honeycomb cores under blast loading. Based on the experiments, corresponding finite element simulations have been undertaken using the LS-DYNA software. It is observed that the core compression stage was coupled with the fluid–structure interaction stage, and the compression of the core layer decreased from the central to the peripheral zone. The blast resistance capability of sandwich panels was moderately sensitive to the core relative density and graded distribution. For the graded panels with relative density descending core arrangement, the core plastic energy dissipation and the transmitted force attenuation were larger than that of the ungraded ones under the same loading condition. The graded sandwich panels, especially for relative density descending core arrangement, would display a better blast resistance than the ungraded ones at a specific loading region.     

考虑反复加载时混凝土损伤积累的RC平板及剪力墙的有限元分析模型的开发

反复荷载作用下的混凝土、钢筋的本构模型是评价和分析钢筋混凝土(RC)结构的承载力-变形特性关键,旨在开发适用于反复荷载作用下RC平板、剪力墙的2维非线性有限元分析的材料本构模型,探讨并推出了反复荷载作用下在混凝土的本构模型中考虑混凝土损伤积累的方法;并对RC平板和剪力墙进行了反复加载的2维有限元模拟。分析结果与实验结果的比较表明,采用所建议的考虑损伤积累的2维非线性有限元分析模型由加载至最大承载力前能很好的模拟反复加载时RC平板、剪力墙的非线性特性。     

Analysis and interpretation of a test for characterizing the response of sandwich panels to water blast

Metallic sandwich panels are more effective at resisting underwater blast than monolithic plates at equivalent mass/area. The present assessment of this benefit is based on a recent experimental study of the water blast loading of a sandwich panel with a multilayered core, using a Dyno-crusher test. The tests affirm that the transmitted pressure and impulse are significantly reduced when a solid cylinder is replaced by the sandwich panel. In order to fully understand the observations and measurements, a dynamic finite element analysis of the experiment has been conducted. The simulations reveal that the apparatus has strong influence on the measurements. Analytic representations of the test have been developed, based on a modified-Taylor fluid/structure interaction model. Good agreement with the finite element results and the measurements indicates that the analytic model has acceptable fidelity, enabling it to be used to understand trends in the response of multilayer cores to water blast.     

Failure analysis of UHPFRC panels subjected to aircraft engine model impact

Using the finite element approach, this paper evaluates the punching resistance of ultra-high performance fiber reinforced concrete (UHPFRC) panels subjected to the impact of an aircraft engine. The models are analyzed using LS-DYNA, a commercially available software program. The structural components of the UHPFRC panels, aircraft engine model, and their contacts are fully modeled. Included in the analysis is material nonlinearity, which considers damage and failure. The analysis results are then verified with the test results. A parametric study with varying fiber contents is carried out to investigate the punching behavior of the UHPFRC panels under aircraft engine impact. The penetration depth, residual velocity of the aircraft engine, scabbing area, and failure mode of various UHPFRC panels are examined. Punching resistance capacities of reinforced concrete (RC) and steel plated concrete (SC) panels are also investigated in this study.     

Inelastic deformation and failure of profiled stainless steel blast wall panels. Part II: analytical modelling considerations

This three-part article presents the results of experimental, analytical and numerical studies on the response of 1/4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reports on the experimental investigations, whilst the analytical modelling considerations are examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action.     

高强钢筋混凝土墙板受力过程简化计算方法

在钢筋混凝土转动角软化桁架模型的基础上,推导出从应力到应变的简化计算方法来模拟高强钢筋混凝土墙板受力全过程。提出计算方法的计算结果与8个墙板的试验结果吻合较好,且比其它学者提出的从应变到应力的计算方法计算简便。研究结果为高强钢筋混凝土墙板的设计和承载力验算提供参考。     

Response of flexible sandwich-type panels to blast loading

This paper reports on experimental and numerical investigations into the response of flexible sandwich-type panels when subjected to blast loading. The response of sandwich-type panels with steel plates and polystyrene cores are compared to panels with steel face plates and aluminium honeycomb cores. Panels are loaded by detonating plastic explosive discs in close proximity to the front face of the panel. The numerical model is used to explain the stress attenuation and enhancement of the panels with different cores when subjected to blast induced dynamic loading. The permanent deflection of the back plate is determined by the velocity attenuation properties (and hence the transmitted stress pulse) of the core. Core efficiency in terms of energy absorption is an important factor for thicker cores. For panels of comparable mass, those with aluminium honeycomb cores perform “better” than those with polystyrene cores.     

Numerical prediction of concrete slab response to blast loading

In this paper, a dynamic plastic damage model for concrete material has been employed to estimate responses of both an ordinary reinforced concrete slab and a high strength steel fibre concrete slab subjected to blast loading. In the concrete material model, the strength envelope is a damage-based modified piece-wise Drucker–Prager model; the strain rate effect on tension and compression are considered separately; the damage variable is based on Mazars’ damage model, which is a combination of tensile and compressive damage. The equation of state (EOS) is also a combination of the porous and solid EOS of concrete with different forms for tension and compression states. The interaction between the blast wave and the concrete slab is considered in the 3D simulation. In the first stage, the initial detonation and blast wave propagation is modelled in a 2D simulation before the blast wave reaches the concrete slab, then the results obtained from the 2D calculation are remapped to a 3D model. The calculated blast load is compared with that obtained from TM5-1300. The numerical results of the concrete slab response are compared with the explosive tests carried out in the Weapons System Division, Defence Science and Technology Organisation, Department of Defence, Australia. Repetitive applications of blast loading on slabs are also simulated and the results compared with test data.     

超高性能混凝土在埋置炸药下的抗爆试验及数值模拟

该文研究了超高性能混凝土在埋置炸药爆炸载荷作用下的动态力学性能和损伤规律。通过改变混凝土靶体的配合比和炸药放置深度,得到了不同试验条件下混凝土靶体的破坏数据,采用非线性有限元法对靶体的毁伤效果进行了数值模拟,模拟结果与实际情况吻合较好。研究结果表明混杂纤维增强的超高性能混凝土具备更加优异的抗爆炸性能,炸药在靶体中的放置深度对混凝土的抗爆性能有显著影响。     

爆炸荷载作用下钢筋混凝土结构的动态响应与破坏模式的数值分析

在爆炸荷载(尤其是脉冲荷载)作用下,除了常见的弯曲破坏形态之外,钢筋混凝土结构还可能发生直剪破坏和弯剪破坏。如何准确地预测爆炸荷载作用下的钢筋混凝土结构动态响应和破坏特征是当前抗爆结构领域十分关注的课题之一。该文介绍作者近年来在这方面的一些研究成果,主要有:将三参数形式的应变速率型材料模型推广应用于二维状态下的混凝土本构关系,建立了弹粘塑性混凝土结构有限元分析方法;基于Timoshenko梁理论和弹粘塑性理论,分别采用有限差分法和有限元法,建立了土中浅埋钢筋混凝土结构动力响应和破坏模式的有限差分和有限元分析方法。对爆炸荷载作用下的典型钢筋混凝土结构计算结果表明:基于Timoshenko梁理论的有限差分分析方法和有限元分析方法能较好地模拟梁的动态响应和弯曲、弯剪以及直剪的破坏模式,而二维弹粘塑性混凝土结构有限元分析方法只能较好地模拟梁的弯曲破坏模式。     

基于装配式技术加固的砌体墙片的力学性能研究

基于装配式技术的砌体结构加固方案可以有效提高结构的抗震能力。采用预制钢筋混凝土墙板对原有的砌体墙片进行双面外贴加固,并用销键、灌浆、后浇带等连接方式保证砌体墙片与预制钢筋混凝土墙板的共同工作。该文通过非线性有限元模型分析了未加固砌体及加固砌体结构在循环往复加载下的力学行为,探讨混凝土墙板和砌体砖墙之间的传力途径,验证加固方法和三种连接措施的有效性。分析证明:采用预制钢筋混凝土贴墙墙板的加固方案可以显著提高砌体结构的抗震性能,强度提高3倍~4倍,刚度提高2倍~3倍,满足现行抗震规范的要求。三种连接方式中,后浇带最有效,在弹性阶段传递了70%的荷载,在后期传递了80%的荷载。