整体结构混合火灾试验原理及数值仿真分析

Methodology and Numerical Analysis of Hybrid Fire Test for Whole Structure

火灾下建筑结构的力学分析分为2个层次:1受火作用的结构基本构件的力学分析,如受火梁、柱、楼板分析;2受火构件力学状态的变化对整体结构影响的力学分析,如火灾下建筑结构的连续性倒塌分析。为考察整体结构在火灾下的力学反应,Mostafaei提出了混合火灾试验方法,即对原结构部分构件进行耐火试验,剩余子结构则采用数值分析。通过构件火灾试验与子结构数值模型间的数据交互反馈,模拟整体结构火灾下的力学反应,进而避免直接进行大型结构整体火灾试验。理论上,如果受火构件与无该构件的子结构模型,在任意火灾时刻时的内力、位移均相等,则该结果与整体结构实际火灾下的反应相同。但实际上,由于无法保持任意时刻受火构件与子结构模型的荷载、位移一致,混合火灾试验简化为每间隔时间Δt或温度ΔT对这些参量进行一次同步。给出了构件试验和子结构数值模型间的数据交换路径,并以基本构件的数值试验代替真实火灾试验,通过混合火灾数值试验与子结构模型的交互分析结果,验证了混合火灾试验方法的准确性。

Mechanical analysis of structures under fire can be divided into two levels： the junior is fire analysis of separated member, such as mechanical analysis of beam, column or slab under fire, and the further is whole structure under fire, such as structural progressive collapse under fire. Whole structure fire test is more accordant with practical structures, but also more expensive compared with separated member fire test. Thus, hybrid fire test was proposed by Mosta- faei. This new test method combines fire test with numerical analysis, which means the separated member will still be tested in furnace, while the remaining structure will be analyzed in computer, with synchronization of certain items at certain time or temperature. Theoretically, the mechanical response of whole structure under fire will be the same with that measured in hybrid fire test, if the forces and displacements are the same between separated member in fire test and remaining structure in computer during the fire. However, the loading condition and boundary condition cannot be adjusted at any time during fire, so those variables will be changed in certain time intervals or temperature intervals. To validate and pre-realize hybrid fire test, the separated column fire test is simulated by numerical software, then an interactive procedure between separated column and remaining structure will be executed. The hybrid fire test results are in good accordance with whole structures response under fire, which shows a convenient and cheap alternative way to substitute whole structure fire test.