脉冲荷载作用下土中浅埋钢筋混凝土框架直剪破坏分析(Ⅱ.应用)

本文应用文献[5]所提出的计算方法，分析了集团装药爆炸条件下土中浅埋框架迎爆面构件的动力响应及破坏模式，并分析了影响结构直剪破坏的因素。最后通过大量计算，给出了集团装药爆炸条件下土中浅埋钢筋混凝土框架发生直剪破坏的条件。     

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。     

爆炸荷载作用下钢筋混凝土梁破坏形态有限元分析

在持续时间较长的爆炸荷载作用下,钢筋混凝土框架或梁通常会发生常见的弯曲破坏形态,但是在持续时间较短的爆炸荷载,如化学爆炸产生的脉冲荷载作用下,钢筋混凝土结构有可能在弯曲破坏发生之前产生剪切破坏。这种现象已被室内外试验所证实,其原因是脉冲荷载激发了结构中的剪力,从而使结构产生剪切破坏。为了预报钢筋单纯凝土梁在爆炸荷载下的响应破坏形态,本文提出了一种基于Ｔｉｍｏｓｈｅｎｋｏ梁理论的非线性分层梁有限元法。在材料模型中考虑了混凝土和钢盘的右面线性和应变速率效应等因素。应用这方法,本文计算分析了爆炸荷载作用下钢筋混凝土梁的动态响应以及弯曲、弯剪和剪切等不同的破坏形态,计算预报的结构动态响应和破坏形态与现场试验结果有较好的一致性。     

爆炸荷载作用下防护门反弹效应的影响因素分析

防护门在常规武器爆炸荷载作用下将发生反弹效应,门体将承受反弹所引起的较大反向应力,反弹力达到一定程度,铰页和闭锁在反弹力的作用下就会先于门扇主体发生破坏。该文推导了爆炸荷载作用下防护门反弹力的解析计算公式,分析了各种因素,包括：边长比、荷载作用时间、阻尼比、荷载形式以及冲击波负压等对反弹效应的影响规律,结果表明：随着边...     

爆炸荷载作用下承重柱的弹性动力响应分析

为了建立爆炸荷载作用下承重柱构件的弹性动力响应分析方法,进一步奠定研究承重柱非线性抗爆响应和破坏形态的理论基础,该文将承重柱简化为承受轴向荷载的约束梁构件,并基于经典Timoshenko梁理论,通过建立等效频率矩阵、等效荷载向量矩阵以及修正的等效质量矩阵,采用变量分离法联立方程求解,推导出承受恒定轴力的Timoshenko梁在任意横向爆炸荷载作用下的弹性动力响应的解析解;并以此弹性解析方法为基础,进一步分析讨论了爆炸荷载作用下,长细比、初始轴向应变、端部约束条件及荷载参数等因素对承重柱弹性动态响应的影响,研究结果对钢柱或钢筋混凝土柱(RC柱)的抗爆分析与设计有参考作用。     

考虑面力作用的HFR-LWC梁抗爆试验研究

实际工程中,面力作用会导致梁板构件的承载力提高以及破坏模式改变。为确切把握面力作用在爆炸加载全过程的变化规律及其对结构抗力的影响,该文进行了混杂纤维轻骨料混凝土（HFR-LWC）梁抗爆性能试验研究,得到爆炸荷载超压时程曲线及梁跨中位移、破坏模式等试验数据,结合端部约束刚度计算方法分析了面力作用对HFR-LWC梁抗力及破坏形态的影响规律。结果表明:试验装置可以合理模拟爆炸加载过程中梁构件的面力作用,是一套定量评估面力贡献的有效工具。面力作用能有效阻止纵向钢筋过早进入屈服状态,充分发挥混凝土的抗压性能,抑制裂缝的开展,有效减小梁的跨中位移,从而提高HFR-LWC梁的抗爆能力。     

埋地管道爆炸地冲击作用的试验研究

利用DASP采集分析系统对常规武器或TNT药柱土中爆炸地冲击作用下引起埋地管道上的动应力进行了测试分析,得出了常规武器钻地爆炸地冲击作用下,正对爆心的埋地管段背面部分因弯曲易受到轴向拉应力破坏,且受力过程是瞬态受力过程的结论。利用LS-DYNA3D有限元程序对埋地管道爆炸地冲击作用影响进行了数值模拟分析,并与测试结果进行了比较,效果较好。     

工字形钢柱的爆炸作用分布特征与计算研究

为研究工字形钢柱上的爆炸荷载特征,明确在不同爆炸条件下工字形钢柱的破坏形式,通过数值计算和试验数据相结合,在三种不同爆炸类型条件下,对钢柱不同位置测点的冲击波曲线形式进行分析,并对钢柱不同翼缘的爆炸荷载水平及竖向分布形式进行总结,给出工字形钢柱上爆炸作用的确定方法。研究结果表明：当爆炸作用沿钢柱强轴时,荷载在翼缘宽度上可按均匀分布,而随近、中、远爆炸类型的变化,荷载沿钢柱竖向分别呈双曲线、梯形和矩形分布特征,而荷载峰值可按TM5-855中试验数据确定;当爆炸作用沿钢柱弱轴时,荷载在腹板上可按均匀分布,而在翼缘上呈三角形分布特征,荷载峰值可按TM5-855中试验数据值乘以相应的放大系数得到;爆炸荷载对钢柱响应形式影响显著,随着爆炸距离的增大,钢柱由局部破坏向整体破坏转变。     

可燃气体爆炸时作用在结构上荷载的研究

本文结合具体工程实例，分析了汽油－空气混合气体容器爆炸时作用在结构上的爆炸荷载效应，包括正相压力，负相压力，冲量，作用时间等。研究表明容器位置不同，所产生的爆炸荷载也不同，板梁结构板形要求不同，其等效静荷载也不同，最合校核了楼板的配筋情况。     

爆破冲击荷载下混凝土T梁桥实验

为了揭示爆破荷载作用下混凝土T梁桥的动态响应及破坏律,制作了两种不同纵向长度的混凝土T梁桥模型,测量T梁桥模型的应变值,以及爆炸前后模型的加速度值和声波速度,进行分析比较。研究表明,T梁桥模型的动态响应在横向1/4处比梁中心更敏感;纵向长度长的混凝土T梁桥在相同荷载作用下更容易发生破坏;混凝土T梁桥在存在损伤积累以后,梁肋板更容易先破坏;这为桥梁抢修和设计提供依据,提高其抗爆性。     

Dynamic failure analysis of renewable energy systems in the remote offshore environments

For effective integrity management of marine renewable energy systems in the dynamic and uncertain ocean environments, understanding the failure dynamics is crucial. The cost of investment in marine/offshore renewable energy infrastructures and the associated cost due to failure and loss of energy production necessitate a predictive monitoring methodology that is dynamic and adaptive. This paper presents an integrated multi-state pure-birth-pure-death Markovian-net profit value model for the offshore turbine subsystem failure analysis and its cost-based consequences. The integrated model captures the offshore turbine subsystem's dynamic failure states and its economic implications due to the cost of energy loss and downtime for the period under consideration. The model applies a phase-type exponential distribution to describe the monotonic state of failure. The methodology is demonstrated with an offshore wind turbine gearbox, and it captures the dynamic state of the system and its failure mechanisms. The cumulative effect of the subelements deterioration decreases the gearbox performance by over 35% within the first 2 years of operation.     

An evaluation of the MPM for simulating dynamic failure with damage diffusion

For dynamic brittle failure, conventional mesh-based methods, such as the finite element method and finite difference method, are handicapped when localized large deformations and subsequent transitions from continuous to discontinuous failure modes occur. To evaluate the potential of the material point method (MPM) in simulating dynamic brittle failure involving different failure modes, the essential features of the MPM are explored for wave and impact problems, and combined wave and diffusion problems are then solved by using the MPM. Through the comparison with the experimental, analytical and numerical data available, it appears that the MPM is a robust tool to simulate multi-physics problems such as dynamic failure under impact.     

Prediction of structural dynamic plastic shear failure by Johnson’s damage number

It is proved that Johnson’s damage number is the sole similarity parameter for dynamic plastic shear failure of structures loaded impulsively, therefore, dynamic plastic shear failure can be understood when damage number reaches a critical value. It is suggested that the damage number be generally used to predict the dynamic plastic shear failure of structures under various kinds of dynamic loads (impulsive loading, rectangular pressure pulse, exponential pressure pulse, etc.,). One of the advantages for using the damage number to predict such kind of failure is that it is conveniently used for dissimilar material modeling.     

Initial and progressive failure analysis of laminated composite structures under dynamic loading

The problem of theoretical prediction of the initial failure and ply-by-ply failure processes in laminated composite structures under dynamic loading is under consideration. A history of deformation can be predicted at any point of a structure using the proposed analytical techniques. The phenometological. second-order tensor-polynomial and maximum stress failure criteria are used to calculate the lower bound of an applied dynamic load. This lower bound corresponds to a start of failure in a structural part. A ply-by-ply failure model is then developed. Using the model, some higher bound for a critical dynamic load impulse value, corresponding to the total exhaustion of a load-bearing capacity by all of the layers in a laminated structure can be predicted. The analysis is applied to thin-walled imperfect laminated graphite/epoxy cylindrical shells, loaded with a short-time impulse of axial compression or external pressure. A general approach to the 3D dynamic deformation analysis of a brick-type mosaic plate and its interaction with a rigid impactor is proposed The approach allows one to model both the initial and damage induced inhomogeneities in a composite structure under dynamic impulsive or impact loading cases.     

Prediction of structural dynamic plastic shear failure by Johnson’s damage number

It is proved that Johnson’s damage number is the sole similarity parameter for dynamic plastic shear failure of structures loaded impulsively, therefore, dynamic plastic shear failure can be understood when damage number reaches a critical value. It is suggested that the damage number be generally used to predict the dynamic plastic shear failure of structures under various kinds of dynamic loads (impulsive loading, rectangular pressure pulse, exponential pressure pulse, etc.,). One of the advantages for using the damage number to predict such kind of failure is that it is conveniently used for dissimilar material modeling.

     

多重四边形环索-张弦穹顶局部断索冲击分析

多重环索-张弦组合屋盖为复杂的弦支穹顶结构。任一拉索瞬断均会对屋盖结构产生十分显著的动力冲击作用。针对多重环索-张弦穹顶屋盖的结构特点,提出基于AP法的断索冲击动力分析方法。针对断索失效路径、断索持续时间、结构阻尼比及屋盖初始荷载等参数开展敏感性分析,得到适用于多重环索-张弦屋盖的断索冲击动力分析的适用参数。剩余屋盖结构的动力分析结果表明:拉索瞬断冲击下,剩余屋盖的位移及内力响应均会不同程度地大于拉索静力失效,拉索瞬断引起的冲击效应不可忽视。而且,部分结构响应的动力放大系数会大显著大于规范所推荐的放大系数DAF=2.0。不同类型的拉索瞬断分析结果表明:同一重环索中任一拉索瞬断引起的动力效应大致相同;外环索瞬断引起的动力效应会显著大于其他拉索;虽然外环索和张弦索的瞬断均会引起较大的动力响应,但是两者的分布规律差异较大;多根拉索瞬断引起的动力响应并非总是大于单根拉索瞬断。     

Dynamic and fatigue compressor blade characteristics during fluid-structure interaction: Part I—Blade modelling and vibration analysis

Fatigue failure in blades resulting from alternating loads is a primary cause of aircraft engine failure. In this study, the dynamic and fatigue performance of a compressor blade, which is prone to fatigue failure in practical use, is verified through numerical analysis and tests to identify specific failure causes and ultimately prevent blade failure. Two companion papers describe this work. Part I—blade modelling and vibration analysis establishes a compressor blade model based on reverse engineering and investigates the blade's dynamic characteristics during aerodynamic and structural behaviour interactions under various flight conditions. To accurately describe the dynamic performance of a real blade, three blade models with different fitting precisions are constructed to support dynamic response analysis. In addition, the flow field of each model is constructed to simulate the aerodynamic loads that cause blade vibration. A numerically based analysis of the fluid-structure interaction is subsequently performed. A reasonable calculation model is selected by comparing the dynamic characteristics among these models. The Campbell diagram is analysed to determine resonance probability, and blade failure cause is ultimately verified based on the vibration analysis. The results show that different accuracies in the blade calculation model produce varying degrees of error; the calculation model's ability to reflect the dynamic and fatigue behaviours of a real blade is recommended to be used as a critical evaluation index in the numerical study. The first-order harmonic resonance occurring at critical speeds may contribute to blade failure.     

风电齿轮箱高速轴圆锥滚子轴承动态特性分析

齿轮箱是风电机组故障率最高的部件之一,其中高达50%的故障停机源于高速轴轴承的过早失效。外部变风载激励和齿轮箱内部激励下,高速轴轴承动载增大,将加速高速轴轴承破坏失效。论文以某750kW风电齿轮箱高速轴圆锥滚子轴承为分析对象,采用ADAMS软件建立圆锥滚子轴承的多体动力学仿真分析模型,研究轴向载荷和径向载荷变化对轴承动态响应特性的影响,基于美国Spectra Quest转子实验台开展了圆锥滚子轴承振动响应特性实验,掌握了圆锥滚子轴承的动态接触力与振动响应变化规律,将为风电齿轮箱高速轴圆锥滚子轴承选型与齿轮箱设计提供理论依据。     

Dynamic behavior of delaminated plates considering progressive failure process

The paper is to study on dynamic response behavior of the delaminated composite plates considering progressive failure process. A formula of element stiffness and mass matrices for the composite laminates is deduced by using the first-order shear deformation theory combined with the selecting numerical integration scheme. A damping model is constituted by a generalized orthogonal damping model on basis of Adams' strain energy method. A virtual interface linear spring element is also employing for avoiding the overlap and penetration phenomenon between the upper and lower sublaminates at the delamination region. The failure analysis method for the delaminated plates under dynamic loading is established by a modified Newmark direct integral method in conjunction with Tsai's failure criterion and corresponding stiffness degradation scheme. By some numerical examples, the effects of frequency of dynamic load, delamination length and location, and reduction of structure stiffness during the progressive failure process upon dynamic behavior of the delaminated composite plates are discussed. The method and conclusions would be useful for composite structures designers.     

凯威特型单层球面网壳在强震下的失效研究

动力强度破坏是网壳结构在遭受地震时的主要失效形式,准确的失效判别需要以基于材料损伤理论的分析为基础。为在动力时程分析中考虑材料损伤累积的因素,编制了基于有限元软件ABAQUS的用户材料子程序,具有较高的计算精度和较好的收敛性,实现了网壳结构考虑材料损伤的动力有限元分析。对单层球面网壳在强震下的失效特点进行了系统的参数研究,探讨了考虑材料损伤因素对网壳失效特征的影响;综合网壳失效时刻的多项特征响应,拟合了能够评估网壳动力损伤程度的损伤模型;基于损伤模型表示的网壳极限状态的物理意义,建立了适用于跨度40m的凯威特单层球面网壳强震失效判别准则,可用之判定网壳在强震作用下的失效极限荷载。