Elastic-plastic Analysis Of Infilled RC Frames Structure’s Seismic Performance

Current design method of reinforced concrete frame structure in China that use pure frame basically is very unreasonable to take the stiffness and bearing capacity contribution of infilled walls and the beam’s bearing capacity contribution of floorslabs into account, which is the major factor of failure in realize the " strong column and weak beam " failure mechanism generally in actual earthquake damage. At the same time, current seismic design in China that use "three seismic fortification criteria" does not make specific provisions of allowable story drift index for "repairable under moderate earthquake"Considering these imperfections of current design method of reinforced concrete frame structure in China, this article carry out related research work as follows:This article analyses and arranges the research findings of experimental and theoretical about the impact of infilled walls and floorslabs on seismic performance of frame structure, and establishes the reasonable finite element analysis models of frame structure that consider the impact of infilled walls. Then, this article makes use of SAP2000V15.1.1to do the mode-superposition response spectrum analysis under frequent earthquake, the elastoplastic time-history analysis under moderate earthquake and the elastoplastic time-history analysis under rare earthquake from multiple perspectives included different seismic fortification intensities, fill rate, position of the weak layer because of no infilled walls, thickness of infilled walls and material of infilled walls. After that, this article studies the stiffness and bearing capacity contribution of infilled walls to reinforced concrete frame structure and compares with current seismic design method in China. Also, this article draws some useful conclusions such as the modificatory reduction factor of natural vibration period by those analyses above.This article makes use of nonlinear stratified shell element in SAP2000V15.1.1that can really simulate floorslabs to establishes the models of frame structure that consider the impact of floorslabs.Then, Pushover analyses of these models were carried out to study the law of floorslabs’participation in tension in the beams’ negative moment area from multiple perspectives included relation between beams and floorslabs, height of beams, span of beams, thickness of floorslabs and clear distance of beams. By quantificationally analysing the scope of floorslabs’ participation in tension in the beams’ negative moment area, this article proposes the value of the effective width of tensile flange; This article proposes allowable story drift index for deformation checking of "repairable under moderate earthquake" so as to improve the quantitative index of "three seismic fortification criteria" in Chinese building Code for reinforced concrete frame structure. Also, this article carries out Pushover analyses to the models of different seismic fortification intensity included the actual frame structures that take the infilled walls and the floorslabs into account, and carries out comparative analyses about the reserve of their ability of anti-collapse under rare earthquake and their seismic performance under frequent earthquake, moderate earthquake and rare earthquake. Then, some useful conclusions were put forward. Lastly, this article proposes a modificatory seismic design method that take the real effect of infilled walls and floorslabs into account and compares design reinforcement with current seismic design method in Chinese building Code. Then, Pushover analyses were carried out to verify that the modificatory seismic design method in this article can meet seismic performance requirements and the feasibility of the allowable story drift index for deformation checking of "repairable under moderate earthquake" in this article.