Abstract:Obtaining a proper displacement time history is the most important procedure in the seismic design of underground rail transit structures when using the response acceleration method. This paper develops a practical method for obtaining displacement time histories by effectively eliminating baseline drift difficulties. The principles and basis of choosing a seismic design method is clarified by presenting the seismic design procedure for underground rail transit structures. Based on expounding the fundamental principles of the response acceleration method, a one-dimensional equivalent linearization approach is proposed. Discussions on the parameters that influence the effectiveness and precision of the calculation results for soil seismic response are presented. For the acceleration time-history curves derived from the one-dimensional soil seismic response calculation, this paper puts forward an approach which eliminates the drifting problem induced by long period random components of acceleration by properly simulating its second-order parabolic baseline equation. Therefore, displacement time history without baseline drift can be obtained by natural integration. Meanwhile, this paper describes the procedure and approach in which the baseline drift problem in an integral displacement time history can be effectively solved by properly applying the numerical analytical software Origin Pro. Taking the Beijing Metro line 3 as an example, this paper illustrates how every pertaining technical procedure and analytical calculation in the response acceleration method can be achieved. This study emphasizes that the analysis of soil seismic response and determination of displacement time histories are relatively complicated and specialistic. Therefore, special analytical engineering consultation work should be carried out accordingly. When the acceleration response spectra and time histories acquired through the one-dimensional soil seismic response approach are objective and reasonable, then the equivalent shear modulus under different probabilities of exceedance applied in FEM are trustworthy. Furthermore, the baseline drift problem must be appropriately handled when displacement time histories are obtained by the integral method. The abovementioned pertaining results are objective and trustful, therefore, soil-underground structure seismic response can be truly simulated by FEM.