Numerical Simulation of Concrete Plate Damaged Under Explosive Loading

The grisliness after-effects can be induced by explosion accident with the collapsing of the structures, the demolishing of the equipments and the casualty of the human beings. Isolation belt constructed between the blast point and the construction is one of the useful design schemes for blast resistance. The nonlinear procedure ANSYS/LSDYNA970 is used to simulate the contact detonation and the isolation belt of blast resistance filled with the air or water respectively. The results indicate that the maximal damage can be caused by the contact detonation, and the isolation belt of blast resistent filled with water can reduce the damage greatly.     

Spallation mechanism of RC slabs under contact detonation

The spallation of the concrete slabs or walls resulting from contact detonation constitutes risk to the personnel and equipment inside the structures because of the high speed concrete fragments even though the overall structures or structural members are not destroyed completely.Correctly predicting the damage caused by any potential contact detonation can lead to better for-tification design to withstand the blast loadings.It is therefore of great significance to study the mechanism involved in the spallation of concrete slabs and walls.Existing studies on this topic of-ten employ simplified material models and 1D wave analysis,which cannot reproduce the realistic response in the spallation process.Numerical simulations are therefore carried out under different contact blast loadings in the free air using LS-DYNA.Sophisticated concrete and reinforcing bar material models are adopted,taking into account the strain rate effect on both tension and com-pression.The erosion technique is used to model the fracture and failure of materials under tensile stress.Full processes of the deformation and dynamic damage of reinforced concrete (RC) slabs and plain concrete slabs are thus observed realistically.It is noted that with the increase of quantity of explosive,the dimensions of damage crater increase and the slabs experience four different damage patterns,namely explosive crater,spalling,perforation,and punching.Comparison be-tween the simulation results of plain concrete slabs and those of RC slabs show that reinforcing bars can enhance the integrity and shearing resistance of the slabs to a certain extent,and mean-while attenuate the ejection velocity and decrease the size of the concrete fragments.Therefore,optimizing reinforcement arrangement can improve the anti-spallation capability of the slabs and walls to a certain extent.     

A Blast Shock Isolation System with MRFD and Its Semi-Active Control Analysis

To effectively reduce the damage to people and devices in civil defense engineering subjected to blast shock, a blast shock isolation system with magnetorheological fluid dampers (MRFD) is proposed. MRFD can provide continuously adjustable Coulomb friction and has many advantages for semi-active control. Numerical simulation of this isolation system is finished using Matlab simulink toolbox. General semi-active control algorithms are consided based on instantaneous optimal active control algorithm. And the results indicate that the shock isolation system can work efficiently, decreasing about 93% of the peak acceleration of the isolation floor.     

Numerical Calculation of Concrete Slab Response to Blast Loading

In the present paper, a dynamic plastic damage model for concrete has been employed to estimate responses of a reinforced concrete slab subjected to blast loading. The interaction between the blast wave and the concrete slab is considered in 3D simulation. In the first stage, the initial detonation and blast wave propagation is modelled in 2D simulation before the blast wave reaches the concrete slab, then the results obtained from 2D calculation are remapped to a 3D model. The calculated blast load is compared with that obtained from TM5-1300. Numerical results of the concrete slab response are compared with the explosive test carried out-in the Weapons System Division, Defence Science and Technology Organisation, Department of Defence, Australia.     

Numerical Calculation of Concrete Slab Response to Blast Loading

In the present paper, a dynamic plastic damage model for concrete has been employed to estimate responses of a reinforced concrete slab subjected to blast loading. The interaction between the blast wave and the concrete slab is considered in 3D simulation. In the first stage, the initial detonation and blast wave propagation is modelled in 2D simulation before the blast wave reaches the concrete slab, then the results obtained from 2D calculation are remapped to a 3D model. The calculated blast load is compared with that obtained from TM5-1300. Numerical results of the concrete slab response are compared with the explosive test carried out- in the Weapons System Division, Defence Science and Technology Organisation, Department of Defence, Australia.     

Risk Assessment and Optimisation of Blast Mitigation Strategies for Design and Strengthening of Built Infrastructure

A probabilistic risk assessment procedure is developed which can predict risks of explosive blast damage to built infrastructure, and when combined with life-cycle cost analysis, the procedure can be used to optimise blast mitigation strategies. The paper focuses on window glazing since this is a load-capacity system which, when subjected to blast loading, has caused significant damage and injury to building occupants. Structural reliability techniques are used to derive blast reliability curves for annealed and toughened glazing subjected to explosive blast for a variety of threat scenarios. The probabilistic analyses include the uncertainties associated with blast modelling, glazing response and glazing failure criteria. Damage risks are calculated for an individual window and for windows in the facade of a multi-storey commercial building. The paper shows an illustrative example of how this information, when combined with risk-based decision-making criteria, can be used to optimise blast mitigation strategies.     

Risk Assessment and Optimisation of Blast Mitigation Strategies for Design and Strengthening of Built Infrastructure

A probabilistic risk assessment procedure is developed which can predict risks of explosive blast damage to built infrastructure, and when combined with life-cycle cost analysis, the procedure can be used to optimise blast mitigation strategies. The paper focuses on window glazing since this is a load-capacity system which, when subjected to blast loading, has caused significant damage and injury to building occupants. Structural reliability techniques are used to derive blast reliability curves for annealed and toughened glazing subjected to explosive blast for a variety of threat scenarios. The probabilistic analyses include the uncertainties associated with blast modelling, glazing response and glazing failure criteria. Damage risks are calculated for an individual window and for windows in the facade of a multi-storey commercial building. The paper shows an illustrative example of how this information, when combined with risk-based decision-making criteria, can be used to optimise blast mitigation strategies.     

Mitigation of Blast Effects on Aluminum Foam Protected Masonry Walls

Terrorist attacks using improvised explosive devices (lED) can result in unreinforced masonry (URM) wall collapse.Protecting URM wall from lED attack is very complicated.An effective solution to mitigate blast effects on URM wall is to retrofit URM walls with metallic foam sheets to absorb blast energy.However,mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world.In this palaer,numerical models are used to simulate the performance of aluminum foam protected URM walls subjected to blast loads.A distinctive model,in which mortar and brick units of masonry are discritized individually,is used to model the performance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model.The aluminum foam is modelled by a nonlinear elastoplastic material model.The material models for masonry,aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads.Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads.     

Mitigation of Blast Effects on Aluminum Foam Protected Masonry Walls

Terrorist attacks using improvised explosive devices (IED) can result in unreinforced ma-sonry (URM) wall collapse. Protecting URM wall from IED attack is very complicated. An effective solution to mitigate blast effects on URM wall is to retrofit URM walls with metallic foam sheets to absorb blast energy. However, mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world. In this paper, numerical models are used to simulate the per-formance of aluminum foam protected URM walls subjected to blast loads. A distinctive model, in which mortar and brick units of masonry are discritized individually, is used to model the perform-ance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model. The aluminum foam is modelled by a nonlinear elas-toplastic material model. The material models for masonry, aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads. Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads.     

爆炸冲击作用下拱顶式储油罐结构的动力响应(英文)

为研究大型钢制拱顶式储油罐在可燃气体爆炸作用下的破坏和变形特征,对多个储油罐缩比模型进行爆炸实验. 并利用 ANSYS/LS-DYNA 软件,建立了缩比为 1: 25 的 5 000 m3储油罐数值模型,对模型在爆炸冲击作用下的破坏过程进行数值模拟. 实验与数值结果表明: 爆炸冲击波对储油罐缩比模型具有瞬间突跃增压的冲击特性,罐壁迎爆面驻点区域超压峰值最高; 迎爆面中部驻点区首先屈服并带动相邻部分达到屈服状态,同时在变形区周围明显形成不规则的塑性铰环,导致罐壁产生内凹屈曲. 在此过程中,罐内液体既对罐壁产生一定的冲击作用,也能吸收和耗散部分爆炸能量.     

Blast protection shelter by using hollow steel filled with recycled concrete

Under extreme loading condition,a shelter will provide a safe place to protect people from injury caused by blast wave and fragments.In order to save resource and reuse waste materi-als,a new design concept for blast protection shelter was explored.The new construction was composed of I-section steel panel or C-channel steel panel filled with recycled concrete aggregate.The compaction process of the recycled concrete aggregate filled in the steel construction was ex-perimentally investigated.A single storey shelter based on the proposed design concept was nu-merically simulated by using LS-DYNA software.In the 3D numerical model,three walls were de-signed using I-section steel and one wall using C-channel steel,and all of the four walls were filled with recycled concrete aggregate.The penetration analysis was done by using ConWep.Some penetration tests were also carried out by using a gas gun.It is found that the proposed shelter based on the design concept is effective for blast protection.     

Analysis of blast wave propagation inside tunnel

The explosion inside tunnel would generate blast wave which transmits through the longitudinal tunnel. Because of the close-in effects of the tunnel and the reflection by the confining tunnel structure, blast wave propagation inside tunnel is distinguished from that in air. When the explosion happens inside tunnel, the overpressure peak is higher than that of explosion happening in air. The continuance time of the blast wave also becomes longer. With the help of the numerical simulation finite element software LS-DYNA, a three-dimensional nonlinear dynamic simulation analysis for an explosion experiment inside tunnel was carried out. LS-DYNA is a fully integrated analysis program specifically designed for nonlinear dynamics and large strain problems. Compared with the experimental results, the simulation results have made the material parameters of numerical simulation model available. By using the model and the same material parameters, many results were adopted by calculating the model under different TNT explosion dynamites. Then the method of dimensional analysis was used for the simulation results. As overpressures of the explosion blast wave are the governing factor in the tunnel responses, a formula for the explosion blast wave over-pressure at a certain distance from the detonation center point inside the tunnel was derived by using the dimensional analysis theory. By comparing the results computed by the formula with experimental results which were obtained before, the formula was proved to be very applicable at some instance. The research may be helpful to estimate rapidly the effect of internal explosion of tunnel on the structure.     

爆炸冲击波在城市地下通道内传播规律的数值模拟

城市地下过街通道是城市重要的交通系统组成部分,也经常会成为恐怖分子爆炸袭击的对象。为了更好的了解爆炸冲击波在地下过街通道中的传播规律,本文通过数值模拟分析了13KG炸药在通道爆炸后冲击波的传播。分析过程中分别考虑了炸药起爆位置及通道顶盖对冲击波传播的影响。分析结果表明当TNT在通道内起爆后,通道顶部的角落将受到更大的冲击波压力作用,当冲击波从出口向外传播时将发生明显的射流现象;当通道出口有顶盖时,炸药在出口的起爆将明显加强通道内部及出口梯道的压力峰值。     

地震次生灾害中地下给排水管道失效模式研究

从砂土液化、基础位移、地震波效应三方面对管道的震害原因进行了分析,结合地下给排水管道的破坏形式,应用单因素分析方法对震害致使管道失效的主要因素进行了研究。研究结果表明:在地震烈度相同、地质构造相近的情况下大管径管道施工中应优先选择预应力钢筋混凝土管;给排水管道采用混凝土带型基础震害率较低;球墨铸铁管管径在DN200时抗震性能最佳。     

Numerical Modeling of Response and Damage of Masonry Walls to Blast Loading

To model the damage process of masonry walls under blast loading, a dynamic continuum damage material model is constructed for brick and mortar separately. The degradation of both the stiffness and strength are governed by a damage variable. By using the proposed material model, damage and fragmentation of a typical masonry wall under blast loading at different scaled distances is calculated. The hazard level of the masonry wall to blast loading is evaluated by analyzing the numerical results.     

Numerical Modeling of Response and Damage of Masonry Walls to Blast Loading

To model the damage process of masonry walls under blast loading, a dynamic continuum damage material model is constructed for brick and mortar separately. The degradation of both the stiffness and strength are governed by a damage variable. By using the proposed material model, damage and fragmentation of a typical masonry wall under blast loading at different scaled distances is calculated. The hazard level of the masonry wall to blast loading is evaluated by analyzing the numerical results.     

Rate-sensitive numerical analysis of dynamic responses of arched blast doors subjected to blast loading

Current practice in analysis and design of blast doors subjected to blast loading considers only simple boundary conditions and material properties. The boundary conditions and material properties, in fact, have considerable influence on the response of blast doors subjected to blast loading. In this paper, the dynamic responses of a reinforced concrete arched blast door under blast loading were analyzed by the finite element program ABAQUS, combined with a previously developed elasto-viscoplastic rate-sensitive material model. And the effect of the surrounding rock mass and contact effect of the doorframe were also taken into account in the simulation. It is demonstrated that the strain-rate effect has considerable influence on the response of reinforced concrete blast door subjected to blast loading and must be taken into account in the analysis.     

Simulation of Blast and Fragment Loading Using a Coupled Multi-Solver Approach

Simulating blast and fragment loading simultaneously in a single computation requires the combined use of multiple states of the art solvers. A pipe bomb is an example of simple improvised explosive device (IED) that consists of a piece of pipe filled with explosive material and capped at both ends. To simulate the explosion of a pipe bomb and the damage it causes, a coupled multisolver approach based upon finite element and finite volume methods is applied. The numerical calculation presented demonstrates the ability of ANSYS AUTODYN(?) to correctly simulate the threats of lEDs and provides insight into how the most significant physical phenomena affect the results.     

沥青路面除冰雪技术研究(英文)

为降低路面和冰雪之间的黏结力,用有机硅憎水材料作为道路表面涂层.有机硅憎水涂层技术的除冰效果用接触角实验和剪切实验来表征,其耐久性用加速加载磨耗实验来评价,而其抗滑性能则用摆式摩擦法和铺砂法来评价.接触角实验结果表明,有机硅憎水涂层材料与水的接触角为100.2°,具有很好的憎水性能.其次,通过剪切实验可以得出:在涂有有机硅憎水材料的情况下,冰层与试件表面的最大剪切应力仅为0.06 MPa,低于没有进行表面涂层处理的最大剪切力3.5 MPa;剪切之后,冰层能够很完整地从试件表面脱落.加速加载磨耗实验表明,在经过一定时间的磨耗之后,残留在沥青路面构造深度里的有机硅涂层材料仍然具有除冰雪的效果.表面涂层后的道路表面的BPN值和构造深度值均有所降低,但是其仍然远远大于规范的要求,确保了安全性.研究表明,沥青道路表面涂层技术能有效地降低沥青路面与冰层的黏结,从而解决冬季道路结冰影响行车安全的问题.     

Analysis on Dynamic Response of Hard-Soft-Hard Sandwich Panel Under Blast Loading

Surface contact explosion experiments have been performed for the study of dynamic response of the hard-soft-hard sandwich panel under blast loading. Experimental results have shown that there are four damage modes, including explosion cratering, scabbing of the backside, radial cracking induced failure and circumferential cracking induced failure. It also illustrates that the foam material sandwiched in the multi-layered media has an important effect on damage patterns. The phenomena encountered have been analyzed by the calculation with ALE method. Meanwhile, the optimal analysis of foam material thickness and position in the sandwich panel were performed in terms of experimental and numerical analysis. The proper thickness proportion of the soft layer is about 20% to the thickness of sandwich panel and the thickness of the upper hard layer and lower hard layer is in the ratio of 7 to 3 under the condition in this paper when the total thickness of soft layer remains constant.