On time-step in structural seismic response analysis under ground displacement/acceleration

                                                                   Tian Yuji and Yang Qingshan

School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China

Abstract: There are two models in use today to analyze structural responses when subjected to earthquake ground
motions, the Displacement Input Model (DIM) and the Acceleration Input Model (AIM). The time steps used in direct
integration methods for these models are analyzed to examine the suitability of DIM. Numerical results are presented and
show that the time-step for DIM is about the same as for AIM, and achieves the same accuracy. This is contrary to previous
research that reported that there are several sources of numerical errors associated with the direct application of earthquake
displacement loading, and a very small time step is required to define the displacement record and to integrate the dynamic
equilibrium equation. It is shown in this paper that DIM is as accurate and suitable as, if not more than, AIM for analyzing the
response of a structure to uniformly distributed and spatially varying ground motions.

Keywords: integration time step; multi-supported structure; displacement input model; acceleration input model;
spatially varying ground motions



กก