重力坝水下接触爆炸的数值分析

采用显式程序AUTODYN中的Euler-Lagrange耦合算法模拟混凝土重力坝水下接触爆炸。研究在不同炸点的水下接触爆炸荷载作用下大坝的动力响应以及损伤裂纹分布特点。针对上述特点采用泡沫铝作为抗爆材料,研究了泡沫铝的抗爆效果。研究结果表明:采用泡沫铝作为大坝水下爆炸抗爆材料能大幅降低爆炸冲击波幅值,减小大坝的动力响应,同时能减小爆炸对坝体产生损伤及裂纹分布范围,具有良好的抗爆性能。     

潜艇艇体结构在水下爆炸冲击载荷作用下损伤研究

采用数值计算和试验手段相结合的方法,对潜艇艇体结构在水下爆炸载荷作用下的损伤进行了研究。利用试验手段确定了潜艇艇体用钢的材料动态性能参数和潜艇典型单元结构在爆炸冲击载荷作用下的开裂判据。采用双层壳体建模方案对潜艇结构进行整艇有限元建模,运用MSC.DYTRAN程序对整艇结构进行水下抗爆仿真。分析了三种不同工况下潜艇艇体结构的损伤形式。本文计算方法和仿真结果可供潜艇水下抗爆设计和潜艇结构生命力评估参考。     

爆炸冲击下水底隧道的动态响应及毁伤模式研究

考虑炸药起爆、冲击波传播、冲击波与结构的相互作用以及结构的动态响应等复杂过程,基于Lagrange-Euler耦合算法,建立了水底隧道水下爆炸的全耦合数值仿真模型。通过与爆炸试验结果进行对比,验证了数值模型的可靠性;研究了水下爆炸冲击荷载作用下的水底隧道的毁伤破坏过程、空间分布规律及破坏模式。结果表明:水底隧道的破坏模式不仅与隧道自身的动力特性有关,还取决于起爆距离及炸药当量等;隧道的破坏模式为局部冲切或剥落破坏、弯曲破坏伴随着局部剥落破坏以及整体弯曲破坏。     

爆炸冲击下水底隧道的动态响应及毁伤模式研究

考虑炸药起爆、冲击波传播、冲击波与结构的相互作用以及结构的动态响应等复杂过程,基于Lagrange-Euler耦合算法,建立了水底隧道水下爆炸的全耦合数值仿真模型。通过与爆炸试验结果进行对比,验证了数值模型的可靠性;研究了水下爆炸冲击荷载作用下的水底隧道的毁伤破坏过程、空间分布规律及破坏模式。结果表明:水底隧道的破坏模式不仅与隧道自身的动力特性有关,还取决于起爆距离及炸药当量等;隧道的破坏模式为局部冲切或剥落破坏、弯曲破坏伴随着局部剥落破坏以及整体弯曲破坏。     

Evaluation of typical concrete material models used in hydrocodes for high dynamic response simulations

With the advancement of the computational capabilities, it is now possible to carry out high fidelity simulation of the complex responses of concrete structures subjected to severe shock and impact loads such as those generated by an explosion. A reliable simulation of the detailed response can play a significant role in the understanding of the physical mechanisms and the development of practical design guidelines based on parametric investigations using validated computational models. Among other influencing factors, a fundamental requirement in simulating concrete structures under shock and impact loadings is a realistic modelling of the behaviour of the concrete material under complex and rapid loading conditions. This paper presents a comprehensive evaluation study of several widely used concrete material models. The model formulations are scrutinized and numerical tests are carried out to examine their actual performances under various loading conditions. Comments on the limitations and the appropriate use of these models are given. Furthermore, a physical explosion test on a concrete slab is simulated to demonstrate the behaviour of the material models in a real application environment. Comparison of the results shows that the Concrete Damage Model implemented in LS-DYNA (material #72) describes the concrete response satisfactorily. Using a modified parameter setting, the RHT model implemented in AUTODYN also exhibits a generally acceptable behaviour.     

高拱坝坝肩接触爆炸毁伤安全评价方法

坝肩稳定是高拱坝结构整体安全运行的基础,尽管高拱坝由于拱形受力特性具有较高的承载能力,但坝肩在遭受爆炸荷载作用后极易发生局部毁伤破坏,从而影响高拱坝结构的整体稳定性。着重对高拱坝遭遇水下接触爆炸毁伤后整体的安全稳定评价方法开展了研究,以刚体极限平衡法为基础,针对坝肩的毁伤破坏特征及毁伤面积,提出了拱圈沿右拱端面抗滑安全系数的评价准则,探讨了拱端面的损伤破坏对高拱坝沿拱端面抗滑稳定的影响。结果表明:坝肩接触爆炸主要引起接触部位坝体的压缩破坏和邻近拱端面的剪切损伤,而拱端面的毁伤将直接降低拱圈沿拱端面的抗滑稳定性,并最终导致高拱坝整体沿拱端面滑动失稳。     

制导炸弹水平侵彻爆炸作用下混凝土重力坝毁伤效应数值仿真

在综合考虑射弹的冲击侵彻作用、破碎弹壳爆炸能损耗、侵彻孔洞对爆轰产物的影响等因素的基础上,通过对制导炸弹GBU-28水平侵彻混凝土重力坝爆炸全过程的三维数值仿真,研究了混凝土重力坝在射弹侵彻爆炸下的动态响应及破坏效应.计算结果表明:侵彻爆炸的毁伤效应主要表现为坝体的局部破坏效应,而且呈现以爆炸作用为主侵彻作用为辅的破坏特征.细长弹药的侵彻爆炸破坏范围的增长主要体现在垂直弹轴方向.     

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.     

水下爆炸作用下固支多层片组结构的塑性毁伤研究

为研究固支多层片组结构在水下爆炸作用下的毁伤行为,以能量法为基础,建立了典型多层片组结构在水下爆炸冲击波作用下的塑性响应模型,给出了一定爆炸载荷迎面作用下固支多层片组结构的塑性变形以及剪切断裂毁伤计算方法。利用AUTODYN仿真软件,对不同工况下固支多层片组结构的毁伤进行了仿真研究,并开展了水下爆炸毁伤试验,测试了水下爆炸冲击波参数和多层片组结构的毁伤情况。结合数值模拟和试验结果可知,该理论模型可以很好的预测多层片组结构的毁伤破坏情况,包括其塑性变形层数、剪切破坏层数和最大破坏深度,为水下多层防护结构抗冲击设计提供了一定的依据。     

Experimental study on scaling of RC beams under close-in blast loading

Damage effects analysis and assessment of buildings under blast loading is an important problem concerned by the area of explosion accident analysis, blast-resistant design, anti-terrorist and military weapon design.The damage character of RC beam under close-in blast loading is investigated through experiments. The damage modes and damage levels of RC beams are studied under different blast loads. The results show that the spallation area increases with the decrease of the scaled distance. The concrete beams are prone to be damaged in flexure mode with concrete crushed on the front face, concrete spallation on the back surface and concrete flake off on the side surface. The scaling of the dynamic response of reinforced concrete beams subjected to close-in blast loadings is also studied. The test results showed a similar macrostructure damage and fracture in all experiment conditions. But the local damage degree of RC beams with smaller size has been reduced a little as compared with that of beams with larger size. Based on the results, empirical equations of the center deflection to height ratio are proposed to correct scaling model considering size effects.     

Comparability research on impulsive response of double stiffened cylindrical shells subjected to underwater explosion

In order to evaluate the strength and comparability of impulsive environment of model and practical structure in the water when subjected to underwater explosion, a new shock factor based on energy acting on the structure is presented to describe the loading of underwater explosion. To test the validity of this new factor, numerical experiments of double stiffened cylindrical shells are carried out a series of cases designed by the new factor and two other standard shock factors respectively. The results of the cases designed by the new factor indicate that the kinetic energy, potential energy and shock response spectrums of the structures agree well with each other in different cases designed by the equal new shock factor. However, the results of the cases designed by the two other standard shock factors are rather diverse. The analysis considers that the old shock factors do not take the spherical characteristics of shock wave front and relative position between detonation and structure into account, which can hardly reflect the similarity of underwater explosion loadings. The new shock factor can make up for such limitations.     

水下爆炸深度对码头框架结构损伤的影响

为了探究水下爆炸冲击作用下框架码头的结构损伤,确定最不利起爆位置,结合实际工程结构,建立了水下爆炸和两层码头框架结构的全耦合模型,验证了所用全耦合建模方法以及所采用材料模型的正确性和可靠性,分析了冲击波传至码头结构时不同深度下码头结构的破坏模式.结果表明:利用全耦合方法以及选取RHT混凝土材料模型来研究爆炸冲击下结构损...     

水下爆炸深度对码头框架结构损伤的影响

为了探究水下爆炸冲击作用下框架码头的结构损伤,确定最不利起爆位置,结合实际工程结构,建立了水下爆炸和两层码头框架结构的全耦合模型,验证了所用全耦合建模方法以及所采用材料模型的正确性和可靠性,分析了冲击波传至码头结构时不同深度下码头结构的破坏模式。结果表明:利用全耦合方法以及选取RHT混凝土材料模型来研究爆炸冲击下结构损伤破坏是准确的,模拟结果也是可信的。随着爆深的增加,码头结构的损伤破坏由局部损伤变为整体损伤再变为局部损伤。当爆深H=7 m位于码头框架结构一层附近时,结构极易发生因位移过大而导致的整体剪切破坏。     

常规面板堆石坝坝前水下防爆距离的确定和影响因素

鉴于混凝土面板堆石坝较弱的抗爆性能,确定合理的坝前水下防爆距离,为坝前水下反恐安全防护设计和预警监测范围提供参考是必要的。选取常规100m级高的面板堆石坝作为分析对象,借助有限元程序Abaqus/Explicit,采用声学介质描述库水,采用大坝-地基-库水系统有限元模型,主要考虑坝前不同距离发生10kg TNT当量水下爆炸,研究混凝土面板的损伤破坏情况及其影响因素。计算结果表明：堆石体变形模量Er、面板竖缝和周边缝摩擦系数fj、面板与堆石体之间摩擦系数fb等三个参数在常规范围内取值不会对最终面板破坏的预测产生质的影响。得到结论：坝前水下防爆距离Dp定为200m是合适的。     

基于小波、小波包两种方法的爆破振动信号对比分析

在小波、小波包的理论基础上,结合某市城市建设中基岩爆破中振动监测数据,采用这两种方法对同一爆破振动信号在信号去噪、对细节信号的处理、信号的分解与重构方面将两种方法的应用和效果进行了对比。分析表明,采用小波包技术研究爆破地震波信号比小波分析技术有更强的灵活性,能更加完整地反映爆破振动信号的特征。     

爆炸荷载作用下坑道结构振动响应及影响因素分析

根据爆炸荷载条件下的模型坑道试验,运用LS-DYNA显式动力分析软件,对试验中典型坑道段在顶爆和侧爆作用下的动力响应进行了数值模拟计算,研究了模型坑道结构在爆炸荷载下的最大振动加速度分布特征,并与试验结果进行了对比验证。结果表明,计算结果和实测结果基本吻合,能够真实反映爆炸荷载下坑道结构的振动响应。最后对不同单个影响坑道振动的截面形状参数进行了一系列数值计算,分析了在相同爆炸荷载下单个特定参数对坑道振动影响规律。     

潜艇典型舱段水下爆炸动态响应分析

基于显式动力学分析程序ANSYS-LSDYNA,对潜艇典型舱段受到水下近场爆炸冲击作用下的非线性动态响应进行了研究。根据水下爆炸理论和数值计算结果,详细探讨了单壳体潜艇水下近场爆炸现象的持续过程,并讨论了冲击波、局部孔穴、气泡运动造成的滞后流等在单壳体潜艇受到水下近场爆炸不同阶段所起的作用。计算了单壳体潜艇受到水下近场爆炸冲击波作用下的响应并与双壳体潜艇的结果进行了对比。本研究对正确理解水下爆炸现象和潜艇的水下爆炸抗冲击设计有重要意义。     

基于SPH-FEM方法的水下近场爆炸数值模拟研究

针对结构水下近场爆炸载荷作用响应求解难点,通过改进的三维轴对称光滑粒子流体动力学方法(Smoothed Particle Hydrodynamics, SPH)计算获得近场爆炸载荷后传输给非线性有限元软件ABAQUS,利用声固耦合模型对结构响应进行时域非线性计算,形成预报水下近场爆炸载荷对结构毁伤的SPH-FEM模型,实现从药包起爆、结构大幅变形、局部撕裂直至完全剪切破坏的全过程模拟,对载荷时历曲线进行试验验证。计算背空矩形钢板在近场爆炸载荷的响应表明,数值结果与试验值吻合良好。SPH-FEM模型计算效率高、可操作性强,易推广至大型复杂结构受水下近场爆炸毁伤的分析与评估。     

Experimental study and numerical simulation of the damage mode of a square reinforced concrete slab under close-in explosion

Terrorist attacks using improvised explosive devices on reinforced concrete buildings generate a rapid release of energy in the form of shock waves. Therefore, analyzing the damage mode and damage mechanism of structures for different blast loadings is important. The current study investigates the behavior of one-way square reinforced concrete (RC) slabs subjected to a blast load through experiments and numerical simulations. The experiments are conducted using four 1000 mm × 1000 mm × 40 mm slabs under close-in blast loading. The blast loads are generated by the detonations of 0.2–0.55 kg trinitrotoluene explosive located at a 0.4 m standoff above the slabs. Different damage levels and modes are observed. Numerical simulation studies of the concrete damage under various blast loadings are also conducted. A three-dimensional solid model, including explosive, air, and RC slab with separated concrete and reinforcing bars, is created to simulate the experiments. The sophisticated concrete and reinforcing bar material models, considering the strain rate effects and the appropriate coupling at the air–solid interface, are applied to simulate the dynamic response of RC slab. The erosion technique is adopted to simulate the damage process. Comparison of the numerical results with experimental data shows a favorable agreement. Based on the experimental and numerical results, the damage criteria are established for different levels of damage. With the increase of the explosive charge, the failure mode of RC slab is shown to gradually change from overall flexure to localized punching failure.     

On attenuation of floating structure response to underwater shock

This paper presents an analysis on attenuation of floating structures response to underwater shock. An explicit finite element approach interfaced with the boundary element method is used for the shock-fluid–structure interaction. The bulk cavitation induced by underwater shock near the free surface is considered in this study. Two types of floating structural configurations are modeled: one is the two-layered panel and the other is the sandwich panel, both of which are extracted from the typical floating hulls—the former corresponds the single hull with coating material and the latter corresponds to the double hull with different material fillings. Their effective structural damping and stiffness are formulated and incorporated in the fluid–structure-coupled equations, which relate the structure response to fluid impulsive loading and are solved using the coupled explicit finite-element and boundary element codes. The cavitation phenomenon near free surface is captured via the present computational procedure. The attenuation effects of the floating structure response to underwater explosion are examined. From the results obtained, some insights on the improvement of floating structures to enhance their resistance to underwater shock are deduced.