Experimental Study On The Progressive Collapse Performance Of Steel-concrete Composite Floor In The Scenario Of An Exterior Column Loss

The failure of some critical bearing members in building structures caused by accidental effects such as explosion and vehicle impact could trigger a progressive collapse of the overall structures.Over the past decades,lots of collapse accidents urge scholars to pay more attention to the design of preventing structural progressive collapse.The steel-concrete composite floor is widely used in steel frames,however,current researches on the progressive collapse performance of the steel-concrete composite floors under an exterior column removal scenario are less.To solve the existing problems,in this paper,experimental studies have been conducted to study the progressive collapse performance of steel-concrete composite floors in the scenario of an exterior steel column loss,the collapse mechanism and working mechanism of the collapse resistance are also analyzed.The main researches are listed as follows:(1)In order to investigate the influence of the floor openings on resisting progressive collapse of composite substructure after the destruction of a key column,two 1 bay×2 bay one-third scale composite floors were tested.The monotonic static load was applied to the top of the failure column to simulate the scenario of the exterior column loss.The results show that the collapse processes of the steel-concrete composite substructures include elastic working stage,elasto-plastic working stage and failure stage.Collapse mechanism such as the membrane effect exist in the process of progressive collapse.The existence of floor opening is not conducive to the formation and development of the membrane effect.The peak load of the specimen with the floor opening is about 85.2%of the specimen without the hole.Buckling of steel beam has a significant adverse effect on the formation of the catenary effect in composite floor.(2)Static collapse test was conducted on one 1 bay×2 bay one-third scale external prestressing composite floors to study the influence of prestress on resisting progressive collapse of the steel-concrete composite floor in the scenario of an exterior column failure.The results show that prestress significantly improve the initial stiffness of composite structure,and it is of great significance to maintain the collapse resistance of the residual structure after the failure of the weld at the end of the steel beam.The buckling of steel beam has an adverse effect on the collapse resistant capacity of the externally prestressed steel-concrete composite floor.(3)Based on the experimental study,the collapse mechanism of the steel-concrete composite floor in the process of collapse is discussed,and a simplified calculation model of the collapse bearing capacity of the steel-concrete composite structure is established.Based on the conservation of energy,the value of dynnamic increase factor when the static analysis method is used to calculate the collapse composite floor is analyzed.The research work in this paper can provide reference for the progressive collapse design of steel-concrete composite floor.