Seismic Design Method Of Reinforcement Concrete Frame Structures Considering Near-field Effects

China,with frequently earthquake,has nearly 500 earthquake fault zones.Many metropolis are located on fault line.The near-field effect has brought tremendous threat to people’s lives and property.In order to consider the near-field effect in seismic design and verify the proposed near-field design spectrum,so we can link near-field design spectrum with the code to guide the design,this paper design reinforced concrete(RC)frame structures according to the current code design spectrum and near-field design spectrum respectively,and then use seismic fragility method based on IDA(Incremental Dynamic Analysis)to obtain the failure probability facing near-field ground motion and far-field ground motion.This paper also use CMR to evaluate the seismic performance of the RC frame structures designed according to different design spectrum.Also,the maximum elastic-plastic story drift of RC frame structures for seismic checking computation is proposed,which takes the near-field effect into account.Through the research,the main research results are summarized as follows:(1)According to the current code design spectrum and near-field design spectrum,a total of 12 reinforced concrete(RC)frames with different earthquake intensities and different floors are designed.The Open Sees finite element models of the structures are established.In addition,their effectiveness is verified.(2)The elastic-plastic time history analysis of the structures is carried out by selecting two kinds of 20 ground motions,whose mean response spectrum is in good agreement with the design response spectrum.The dynamic behavior of reinforced concrete frame structures subjected to two kinds of ground motions is compared.Three main aspects are included in the comparison: maximum top displacement,story drift ratio and maximum top acceleration.Research shows that the damage measure of model facing near-field ground motions is much larger than far-field ground motions.Accordingly,it is necessary to consider the near-field effect for aseismic design.(3)Through IDA analysis and seismic vulnerability analysis,the performance of these structures are evaluated by using Collapse Margin Ratio(CMR)and performance margin ratio.The result shows that the structures designed according to the near-field design spectrum can meet the three level earthquake resistant design requirements in China,but the collapse safety reserve can’t reach the level of current design code in China.Based on the data,relational functions between the performance margin ratio of the near-field and the far-field with different intensities and the maximum story drift are fitted.Therefore,it is suggested that when thenear-field design spectrum is adopted,the maximum elastic-plastic story drift of RC frame structures is 0.015.