Research On The Effect Of Floor Slab On The Collaborative Anti-Continuous Collapse Performance And Dynamic Response Of Reinforced Concrete Structures

Recently there has been a great deal of interest in the issue of structural resistance to continuous collapse.Most of the current conclusions do not take into account the floor slab,leading to some errors in the analytical results.The main work of this paper includes.（1）The calculation equations for the collapse resistance of structures with floor slabs under the compression arch mechanism and the suspension chain line mechanism are derived,and the links between DIF and time to failure and damping ratio;simulations are carried out to simulate the dynamic tests of continuous collapse of beam-column members and simulations of the proposed static tests,which prove the correctness of the finite element units,restraint connections and loading methods selected in this paper.（2）The non-linear dynamic demolition member method was used to compare the variation patterns and differences in vertical displacements,collapse resistance mechanisms and internal forces of key members of the 7-storey RC structure without and with slabs under various operating conditions.The results show that the structure with floor slab reduces the displacements by at least 60.70%,91.78%,86.92% and84.47% respectively than the structure without floor slab under the four working conditions;the corner columns and long-sided centre columns fail,the overhanging chain effect of the floor slab gives full play and the pressure arch mechanism eventually disappears;the short-sided centre columns and internal columns fail,the pressure arch mechanism always does not quit working and the overhanging chain line effect of the slab does not appear.（3）By considering T-section beams with different beam flange widths to simulate the collapse resistance of floor slabs on ordinary rectangular beams,the proposed value of effective flange width of beams with the best agreement with the action of floor slabs and which can significantly reduce the amount of arithmetic is proposed;using non-linear dynamic analysis and Pushdown analysis,the continuous collapse dynamic response of the model with and without floor slabs under several different sets of loads is investigated.The range of DIF without floor slab is 1.10~1.52 and the range of DIF with floor slab is 1.642~1.866.The maximum value of the latter is 22.76% higher than the maximum value of the former.The floor slab can significantly amplify the continuous collapse dynamic response of the structure and enhance the collapse resistance performance.（4）The effects of different floor slab parameters（slab thickness,floor reinforcement ratio,slab reinforcement spacing,floor concrete compressive strength,floor span-to-thickness ratio and floor span number）on the structural collapse resistance load bearing performance and DIF were investigated,and improvement and optimisation were proposed for the range of DIF values for RC structures.The results show that increasing the reinforcement ratio and decreasing the span-thickness ratio can reduce the vertical displacement by 94.62% and 45.68% respectively,and significantly increase the dynamic amplification factor,while the effects of the remaining parameters are relatively small;the improved DIF values for ordinary RC structures in China are proposed to be in the range of 1.744~1.8.