DYNAMIC ANALYSIS METHOD FOR FIRE-INDUCED PROGRESSIVE COLLAPSE OF A PLANAR RC FRAME

Progressive collapse of building structures can be induced by accidental fire. Static analysis is widely used in the traditional fire resistance analysis of buildings to predict the limit state of structures subjected to fire. However, the mechanical behaviour of structures exceeding the limit state should be simulated in a progressive collapse analysis. At this stage, some structural members fail and then lead to a dynamic progressive collapse process. Therefore, the traditional static analysis can not accurately simulate the progressive collapse of building structures in fire. On the other hand, conventional dynamic method is also difficult for the research or engineering application of fire-induced progressive collapse because of the huge unnecessary computing workload in accordance with the long time fire action. In order to solve these problems, an equivalent time method is proposed to significantly reduce the time cost of dynamic analysis for the fire-induced progressive collapse. With this method, an internal computing time is used for the heat transfer analysis, as well as the coupled thermal-mechanical analysis at the material level; whilst an external computing time is used for the mechanical progressive collapse analysis at the structural level. The simulation for an 8-story planar RC frame shows that when a proper ratio of the internal time to the external time is selected, the proposed method can accurately simulate the damage of fire to the structural material, and at the same time significantly reduce the computing time of progressive collapse analysis.