Investigation On Efficiency Of New Ground Motion Intensity Measures And Seismic Fragility Analysis Of Structures Based On IDA

Incremental dynamic analysis method(IDA),as an important approach of structural nonlinear analysis and seismic capacity assessment under earthquake,has attracted the attention of scholars at home and abroad.A large number of studies have shown that in the incremental dynamic analysis,choosing a reasonable ground motion intensity measure(IM)is an effective way to reduce the dispersion of the seismic response results and improve the reliability of the seismic performance analysis and collapse probability assessment results.Based on IDA approach,this paper compares the efficiency of different ground motion intensity measures,and performs the seismic fragility analysis of reinforced concrete(RC)frame structures based on different IMs.The following is the main research content:(1)According to the Chinese current design code,six-,eight-,and ten-story reinforced concrete frame structure models were designed and analyzed by PKPM software.Using OpenSees analysis software,finite element analysis models were built.The first three natural vibration periods of each structure based on two different softwares were compared to verify the rationality of the finite element analysis model in this paper.(2)The efficiency of different ground motion intensity measures was investigated and compared.First,2 new-type ground motion IMs based on mean value of spectral acceleration within a certain period range were proposed.Then,15 chosen original ground motion records were adjusted by intensity measures such as the peak ground acceleration(PGA),the peak ground velocity(PGV),the peak ground displacement(PGD),the damped spectral acceleration Sa(T1,?)corresponding to the fundamental period T1 of the structure,IM parameterINp based on the spectrum shape of acceleration response spectrum,the new IM parameters INp*?INpL.he incremental dynamic analysis was conducted on the three structures with the maximum inter-story drift ratio ?max as the engineering demand parameter(EDP),and IDA curves with 16%,50%and 84%quantile were obtained further.The linear regression analysis was performed on the IDA results to compare the correlation between the above-mentioned IM parameters and the seismic response of the structures.The results shows that selecting INpL taking into account the higher-order mode shapes of the structure and the non-linear period elongation effect as the ground motion intensity measure to adjust ground motion records can effectively reduce the dispersion of the structural nonlinear analysis results.(3)Seismic fragility analysis of the RC frame structure.Based on IDA results,PGA?PGV?Sa(T1,?)?INp?INp*and INpL were used as IM parameters to analyze the seismic fragility of the three structures,and the seismic fragility curves and DS probability curves were drawn.Based on the probabilistic seismic demand analysis,from the perspective of "practicability","effectiveness" and "usefulness",the different ground motion intensity measures were evaluated.And the results of the probability of different limit state and damage state for each structure were compared when the above-mentioned ground motion intensity measures were used to adjust the original ground motion records to small earthquake,moderate earthquake and large earthquakes.The results show that the new ground motion intensity measure INpL has good "practicability","effectiveness and "usefulness".It can effectively improve the reliability of the seismic performance analysis and collapse probability assessment results.However,when PGA and PGV are selected as the ground motion intensity measures for structural seismic fragility analysis,the analysis results are relatively conservative.