Research Of Resisting Progressive Collapse Of Multi-storey Frame Structure Subjected To An Explosion Inside Its Basement

The use of underground structure has become an important means of relieving the housing and traffic tension on the ground.However,in view of the growing worldwide terrorist attacks.Structural damage due to an explosion in the basement brings serious threat to people’s life and property safety,and has attracted great attention of many scholars and researchers in the past years.Based on the explosive mechanics theory,the progressive collapse theory and the finite element method,the damage mechanism、collapse failure process and the main influencing factors of the multi-storey reinforced concrete frame structure under an explosion in its basement are analyzed with ANSYS/LS-DYNA software.The corresponding protection analysis against the structural collapse is also carried out.The primary work and achievements are as follows:(1)The reinforced concrete slab model is established using ANSYS/LS-DYNA software,including the definition of material model and an introduction of fluid-structure coupling algorithm.The accuracy and efficiency of fluid-structure coupling analysis method were verified through a comparison between the computer results and experimental data.(2)The finite element coupling model is established,including Multi-storey reinforced concrete frame structure with basement using integral model,soil around,air and the explosive.The progressive collapse response of the multi-storey building when the explosion occurred in the first story underground is numerically investigated using three-stage simulation method.(3)By comparing the progressive collapse of the reinforced concrete frame with basement and the same frame without basement when the explosion occurred in the same structural floor,it is revealed that the soil around the basement play a positive role in slowing down the speed of the structure collapse,and then can alleviate the disaster caused by the structure collapse;the destructive degree of the building under an internal explosion confined by surrounding walls is heavier than that without surrounding walls,and the protective measures of underground structures is different from the ground structure;Under the same equivalent explosions,structural damage results caused by an explosion in the first floor underground is more serious than those by an explosion in the second floor underground.(4)Through the analysis and comparison of the damage mechanism and collapse modes of the multi-storey reinforced concrete frame structure,different structure protective measures are chosen,showing the following results.Within the structure column reinforced dispersive distribution can slow the structure collapse speed;Stirrup encryption can enhance structural shear strength to improve its collapse –resistant capability;Increasing the ratio of longitudinal reinforcement of structure column can effectively prevent the structure from progressively collapsing;the protection measures with beam-column joints shows the important role of structure column in resisting the structures from progressive collapsing;Fixed joint with steel plates protection with the steel plate,cannot effectively prevent the structures from progressive collapse while full size steel plate protection with beams and columns can effectively avoid the structural collapse.(5)Through analyzing and comparing the protective effects of different protective measures,some reasonable protection measures are put forward,which not only meet engineering needs,but also are economical.The analysis results can also give some reference for research and engineering applications on the blast-proof of reinforced concrete frames with basements.