Progressive Collapse Analysis And Numerical Simulation For RC Frame Structures Exposed To Fire

Reinforced concrete structure is one of the most widely used structure forms at present, but there is an important problem in the progressive collapse of frame structure that threatens the security of buildings. When exposed to fire, it will reduce sharply in the bearing capacity of the RC frame structure. Once the progressive collapse of frame structure happens with fire, it will bring a serious disaster which is incalculable. In this paper, the author analyzes the progressive collapse of RC frame structures exposed to fire by numerical simulation method. The main works are as follows:(1) According to the variation laws about high temperature mechanical properties of concrete and reinforcement, the author selects the appropriate constitutive relation and solid elements in order to set a model of frame structure. And then the author confirms the feasibility of the model through the comparison between the result of finite element method computation and the result of experiments, based on the experimental data which provided by Tsinghua university.(2) The one-span and two-story RC frame model is studied by finite element method in this paper. The factors that affect the performance of frame structure exposed to fire have been considered, including the points of ignition, the minimum thickness of concrete cover, ratio of reinforcement, stiffness ratio of beam to column and the initial load level. then, the deformation behavior and the changing regularity of mechanics property about beam and column are obtained under each factor.(3) Based on the DCR discriminant criteria of GSA criterion, it assumes that three kinds of working conditions, including the corner column failure, the side column failure, and the central column failure respectively. Then, it analyses the remaining structure’s ability to resist progressive collapse. The study indicates that the failure of central column leads to severe redistribution of internal force and the poor capacity of remaining structure to resist progressive collapse by comparison with the failure of corner column or side column, what’s more, the section under the atmospheric temperature may become the weakest point.Through the research, some effective measures are proposed in order to provide valuable references about structural design, which can improve the overall performance of fire resistance and the ability to resist progressive collapse in the structure.