冲击与火载荷作用下约束构件的响应和屈曲研究

Based on the engineering background of structural fire resistant and blast resistant design, the steel members with elastic restraint such as beams and columns are taken as the objects of study, the response and failure behavior of the structures under blast and fire loading is going to be investigated, the focus of research is on the restraint effects for the response and buckling behavior of steel members. In order to carry out accurate and effective response assessment and the critical temperature prediction, an united computing model for the response of restrained beams and columns under blast and fire is going to be established by using the minimum principle of acceleration in dynamics of elastic-plastic continua at finite deformation, the effects of the large deflection, strain rate and thermal expansion deformation will be included, in coordination with the constitutive equations related to temperature, then the finite difference technique can be presented, the large deflection behavior and catenary action effects of the steel members under impact and fire loading can be adequately expressed by this method. To further analyze the influence of constraint stiffness on the behaviour of beams and columns, finite element simulation and the experiment analysis will be implemented for the frame structures with three types of beam-column connections, which are rigid, semi-rigid and flexible,respectively, and the effects of connection between beam and column will be discussed. Through comprehensive comparison in both aspects of numerical simulation and experiment and analogy analysis for the restained members and frame, the relation between the constrain stiffness of connection and the limiting temperature of the structure under impact and fire would be clarified,the theoretical basis to simplify the calculation of the structural fire resistance and blast resistance would be provided.

基于结构抗火和抗爆工程背景，以端部具有弹性约束的梁、柱构件作为研究对象，开展结构在爆炸和火作用下的响应机制研究，重点考察构件响应与屈曲行为的端部约束效应。研究内容和手段为：（1）以有限变形动力学中的最小加速度原理为基础，建立爆炸、冲击和火载荷作用下结构行为分析的统一计算模型，该模型考虑大挠度、应变率、热膨胀变形和温度软化效应，构建钢梁动力响应和钢柱屈曲数值模拟的有限差分法，以能够充分描述钢构件受火和冲击作用下的大挠度行为和悬链线效应，从而开展准确有效的响应行为评估和临界温度、爆炸极限预测；（2）对于具有刚性、半刚性和柔性三种连接类型的框架结构，通过有限元模拟和实验量测，讨论连接效应，以分析不同的约束刚度对于框架中梁、柱行为的影响。通过上述两方面对约束构件和框架行为模拟与实验分析的综合比较及比拟研究，阐明约束刚度与火和冲击共同作用下结构极限温度的关系，为结构抗火和抗爆简化计算提供参考依据。

以‘911事件’为典型代表的工程结构连续倒塌问题，导致学术界对其基本构件如梁、柱及其梁-柱连接性能的追问。基于以上背景，本项目将端部具有弹性约束的梁、柱构件和梁-柱间具有不同类型连接的单层框架作为研究对象，开展结构在爆炸和火作用下的响应机制研究，重点考察构件响应与屈曲行为的端部约束效应。主要研究内容为：（1）对于具有弹性约束的梁、柱构件，建立能够有效模拟其在火、爆炸、冲击等多重载荷作用下的响应和失效行为的分析手段。（2）运用所建立的分析手段进行参数研究，考察火与冲击两类载荷的相互作用效应。（3）对于具有刚性、半刚性和柔性三种连接类型的框架结构，通过有限元模拟和实验量测，讨论连接效应，以分析不同的约束刚度对于框架中梁、柱行为的影响。与以上研究内容相对应，所取得的重要结果为：（1）分别以有限变形动力学中的最小加速度原理和变形后构型为基础，建立了爆炸、冲击和火载荷作用下结构行为分析的统一计算模型，能够充分描述构件受火和冲击作用下的大变形行为、悬链线效应和端部约束效应；提出了受横向冲击约束梁柱构件的单自由度模型，简化了计算过程。（2）通过参数研究，全面考察端部轴向和转动约束刚度对于钢梁、柱响应和屈曲行为的影响，即考察构件极限温度、爆炸极限和临界冲量的端部约束效应；还给出了一个简单公式计算火与冲击作用下钢梁的永久变形。（3）完成了常温下不同连接类型的钢框架结构的冲击实验，检验了有限元模拟的有效性。初步建立了火与冲击共同加载实验系统。上述工作的意义在于，所建立的火与冲击多重载荷作用下约束构件的计算模型，弥补了有限元法的不足，而自主设计建造的实验系统也填补了当前该领域的空白。无疑地,所得到的研究结果和结论将为结构抗火和抗冲击简化计算提供参考依据。