Research Of Resisting Progressive Collapse Of Underground Frame Structure Subjected To Internal Blast Load

In the new century,people’s living quality standard continues to improve, people’s living region is not only focused on the ground, but also more and more people pay attention to underground space structure. Meanwhile, Terrorists increasingly choose high-explosive material to threaten people’s lives and property safety. Once the explosion occurres underground space structure and then causes progressive collapse, it will cause huge losses to people’s lives and property. This paper applies ANSYS / LS-DYNA software to analyze the failure mechanism of progressive collapse and dynamic response under multiple protective measures when underground reinforced concrete frame structure is subjected to explosive impact load. The main research work and achievements are as follows:(1) This paper adopts separated modeling method to establish a finite element model including underground reinforced concrete frame, surrounding soil, the equivalent boundary element, air, explosive and then respectively uses Direct Simulation Method, Alternative Load Path Method and Three-Stage Simulation Method to analyze progressive collapse process. By comparing and analyzing results obtained by the three methods, the paper verifies the validity and reasonableness of Three-Stage Simulation Method.(2) The paper applies Three-Stage Simulation Method and separated modeling method to respectively establish finite element model when explosive is located in different positions of the bottom of underground reinforced concrete frame structure, analyzes failure mechanism and collapse mechanism of underground reinforced concrete frame structure and dynamic response of surrounding soil when explosive explodes in different positions.(3) By strengthening region near nodes(for example improve structure’s reinforcement ratio of longitudinal reinforcement and stirrup to enhance the structural integrity), the paper analyzes failure mechanism and collapse mechanism of underground reinforced concrete frame structure and dynamic response of surrounding soil when explosive explodes in different positions.The results show that: protection method that strengthens region near nodes can effectively delay or prevent progressive collapse of structures under blast load.(4) Through analyzing and contrasting protective effect of protective measures when explosive is in the same location, the paper tries to find out protective measures that not only meets engineering needs, but also is economical and reasonable, in order to apply in engineering practice furtherly.(5) By studying progressive collapse and protection process of underground reinforced concrete frame structures under different protection types, the paper can provide some guidance for the progressive collapse study and protective measures of underground structures.