面向框架整体结构的多尺度并行协同分析抗火混合试验关键技术研究

Due to the restraint effect caused by conjoined members, the fire resistance test based on components can not reflect its real performance in the whole building. Hybrid fire testing (HFT) developed recently is one of the hot spots to solve the above problems, but the boundary condition of experimental substructures is too simple, and the numerical part fails to consider regional fire effects, which are different from the actual stress state of the whole building . A HFT system is established in this project, and the three-story steel frame is taken as the benchmark model. The axial restraint column, axial and bending double constraint column, sub-frame are taken as the experimental substructure, which is placed in fire furniture to conduct a fire test. The restportionare divided into microscope/microscope normal temperature numerical substructure, which are analyzed simultaneously based on multi-scale finite element model and parallel computation. The experimental substructure and the numerical substructure exchange data in real time through the control center to ensure the synchronization of time domain. A multi-scale collaborative analysis HFT method which integrates the test and numerical analysis is put forward, it can be employed to assess the performance of the whole structure for a fire scenario, or to evaluate the behavior of a single element, in light of the interaction between components of the structure. HFT would simulate the behavior of the whole building under fire with much lower cost and more comprehensive results than the direct full-scale test method can be obtained. The existing fire testing equipment is effectively used to realize the overall fire test of the complex large-scale structure with the substructure hybrid fire testing.

由于受到相邻构件约束，基于构件的抗火试验无法反映其在整体结构中的真实性能，最近发展的抗火混合试验是解决上述问题的研究热点之一，但其试验部分边界条件过于简化，数值部分未能考虑区域火场影响，与火灾中整体结构实际受力状态存在一定差异。.本项目建立抗火混合试验系统，取三层钢框架为基准研究对象，以轴向约束柱、轴向弯曲约束柱和子框架作为试验子结构，置于抗火炉内进行等效边界条件下火灾全过程试验；其余部分划分为微观高温/宏观常温数值子结构，基于多尺度模型和并行计算进行有限元分析；试验子结构和数值子结构通过控制中心进行实时数据交换并保证时间域同步；提出一种试验与数值集成的多尺度协同分析抗火混合试验方法，既可以研究区域火灾下整体结构的抗火性能，又可以评估与相邻构件交互作用下的单独构件抗火能力；以较低成本实现更高可靠性的整体结构抗火分析，有效利用现有抗火试验设备，通过构件子结构试验实现复杂大型结构整体火灾试验。

针对整体结构火灾试验成本高昂、构件火灾试验边界条件恒定等问题，本项目目的是利用边界条件可交互的构件子结构试验实现与局部受火工况下整体结构火灾试验相近的抗火性能评估，即以较低成本实现更高可靠性的整体结构抗火分析，有效利用现有抗火试验设备。. 本项目采用理论分析、数值模拟和试验相结合方法探索了抗火混合试验技术：1）基于重叠域分割方法进行了等效构件与实际构件边界条件、子结构输入输出的相互转换，建立了抗火混合试验系统；2）通过调整高温下时间和温度场相似关系使得弹性状态下缩尺模型和足尺模型力学性能能够相似；3）以钢框架、连柱钢框架和钢筋混凝土框架为例证实多尺度混合模型的可行性和有效性；4）将分割界面延伸至上层柱的中点以及两侧梁的反弯点处能够有效解决受火柱柱顶弯矩无法施加的问题，研究结果证实了考虑约束条件的抗火混合试验的可行性；5）验证多尺度建模方法能够保证精度同时极大提高计算效率（本项目75%以上）；6）多尺度抗火混合试验方法能较好的反映整体结构在火灾下的力学性能，通过试验子结构与数值子结构的边界条件交互，能够较为近似的得到和整体结构相近的结果；7）与整体结构及混合试验相比，传统构件受火试验所得耐火极限相对偏低；8）对比三水准设防烈度下火灾的易损曲线，火灾荷载密度为最大值时发生轻微、中等破坏的概率均超过95％且变化范围不大。随着地震烈度的升高，钢框架发生严重破坏和倒塌破坏的超越概率也随之增大。. 本项目提出一种试验与数值集成的多尺度协同分析抗火混合试验方法，既可以研究区域火灾下整体结构的抗火性能，又可以评估与相邻构件交互作用下的单独构件抗火能力。本研究中抗火混合试验技术及约束子结构边界条件简化方法可为国内抗火实验设备的新建及升级改造提供示范和参考作用。.