Modified equation for long period part of design response spectrum of an isolated structure

Based on a single-mass model,the earthquake responses of isolation structures with different natural periods were analyzed by using the equivalent linearization method and the time history analysis method according to China,Japan and USA codes.Through comparison of acceleration response spectra,it was found that the response spectrum of the long period part of the design response spectrum in China code is too large.According to the results of time history analysis,the modified equation for the long period part was proposed based on the original acceleration response spectrum.Finally,the earthquake response of an isolation structure was computed by using the new modified acceleration response equation and the time history analysis method,and the results obtained with the modified long period response spectrum were consist with those of the time history analysis.The response analysis results showed that the proposed equation of response spectrum has higher analysis precision for isolated structures.