Experimental Study On Progressive Collapse Performance Of RC Flat Slab Structures In The Scenario Of Side Column Loss

Progressive collapse accidents would happen in the buildings and structures due to the failure of one or more supporting members under the accidental loads such as impacting or explosion et al.Therefore,domestic and foreign scholars have carried out a large number of experimental and theoretical studies on the progressive collapse performance and collapse mechanism of structure.RC flat slab structure is a common used structural forms,which has the characteristics of convenient construction and flexible layout et al.However,in the scenario of the supporting column loss,the risks of progressive collapse failure due to the smaller redundancy are higher than that of the common RC structure.At present,the experimental studys on the progressive collapse performance of RC flat slab structure are limited,so it is necessary to carry out the research works.In the view of the above problems,this paper discusses the collapse mechanism of RC flat slab structure in the scenario of side column loss using the static loading model,and puts forward some suggestions of design for the collapse resistance.The main works of this paper are as follows:(1)Designed two monolayer RC flat slab substructure specimens as the scale model of 1/3.5,which was two-span in longitudinal direction and one-span in transverse direction,investigated the influence of oblique reinforcement in the slab on the progressive collapse performance of flat slab substructure.The experimental studys showed that:The progressive collapse process of flat slab substructure mainly experienced three stages:elastic stage,eompressive membrane action and plastic hinge line development and formation stage,tension membrane action development and formation stage,respectively;In the ultimate collapse state of flat slab substructure,distribution of main cracks at the top surface of slab was the circular arc with the failure column as the center,at the same time,the bending shear failure occured in the slab-column joints adjacent to the failure column;When reinforcement was arranged obliquely in the slab,the specimen's the first peak load and the load value in collapse limit state was increased by 32.3%and 54.2%,respectively.(2)Designed two monolayer unbonded prestressing concrete flat slab substructure specimens as the scale model of 1/3.5,which was two-span in longitudinal direction and one-span in transverse direction,investigated the influence of unbonded prestressing tendon in the longitudinal column strip and middle strip on the progressive collapse performance of flat slab substructure.The experimental studys showed that:Distribution of cracks in the slab surface was similar to that of the non prestressing flat slab substructure,the bending shear failure occured in the slab-column joints adjacent to the failure column under the collapse load,too;When the unbonded prestressing tendon was arranged in the longitudinal strip,the first peak load and the load value in collapse limit state at most was increased by 65.4%and 58.2%,respectively;compared with the non prestressing flat slab substructure,the prestressing increased the first peak load of specimens remarkably.(3)Through the experiment results,summarized the collapse failure modes of the RC flat slab substructure,analyzed the main collapse mechanism resistance,established a simplified mechanics model for calculating the collapse load resistance,put forward some suggestions and methods for design of the RC flat slab substructure on the progressive collapse resistance.The research results of this paper could provide references for design on the progressive collapse resistance of RC flat slab structure.