Structural Behavior Of Steel Frame-Composite Floor Systems On Progressive Collapse Under Different Column Removal Scenarios

Nowadays,building structures tend to be more complicated and upsizing,and high-rising buildings even skyscrapers are becoming more and more common.The engineers prefer steel structure and steel-concrete composite construction when they design the structure because of steel-concrete composite structure's excellent behaviour.Various loads applied on the structure had been considered at the design stage,but there are still a lot of unpredictable factors,such as gas explosion,vehicle impact,terrorist attack and fires,in reality.These abnormal accidents may lead to initial failure of some structure element.If the partial failure spreads from element to element,it is likely to cause a large part of damage and lead to a progressive collapse of structure.Ronan Point apartment accident in London in 1968 has alerted the engineers for the risk of progressive collapse.Two disastrous collapse accidents happened in America in 1995 and 2001 respectively make people realized the necessity and urgency of against progressive collapse design.Till now,a number of research work has been done on the progressive collapse behaviour and mechanism.However,most experiments focus on two-dimensional structures,which cannot explain the three-dimensional global effect and the influence of slab.Besides,internal column loss is widely researched,but it is under low-risk compared with other column loss scenarios.Above all,this paper conducted experimental tests on the progressive collapse behaviour of 3D steel-frame composite slab system under PIC(penultimate internal column)and CC(corner column)removal scenarios.The detailed research work is listed below:(1)The overall process load-vertical displacement response and failure mode is obtained under two different column loss scenarios.(2)The strain-displacement curves of critical section are analyzed and the load-resisting mechanism is preliminarily discussed.(3)The contribution of flexural action and catenary action of double girder system and double beam system for whole capacity is quantified.(4)Based on the energy method proposed by Izzuddin,the dynamic response of 3D steel-frame composite slab system under PIC and CC removal scenarios is calculated.In addition,DIF is compared with present codes.(5)The component-based model of flush end plate connection and double angle web cleat connection is proposed,and a simplified finite element of 3D skeleton frame is developed.(6)The behaviour of steel frame under PIC and CC column loss scenario is discussed and the effect of deck-concrete composite floor is quantified.Finally,the influence of loading method on the structural behaviour of 3D skeleton frame is analyzed.