Exploring the influence of 1d and 3d velocity profiles on ground response subjected to long-return period seismic loading

Abstract

The seismic design of typical structures in Taiwan is performed by using the design ground motions with return period of 475 years. For critical infrastructure such as nuclear power plant and major transportation hub, design ground motions with longer return period should be used. In addition, site-specific ground response analyses would be performed to obtain the input ground motion histories for the subsequent dynamic time history analyses of the foundations and the super-structures at the same site. Due to the simplicity in code usage and input parameter specification, 1D ground response analysis is preferred in lieu of multi-dimensional ground response analysis. However, for sites with high lateral variability, 1D ground response analysis may not be sufficient in capturing the real ground response. In this study, we explore the difference in the 1D and 3D ground response analysis results when subjected to long-return period seismic motions. Two target sites are considered. Based on thorough geotechnical and geophysical investigation, detailed 3D velocity models would be constructed for both sites. A series of 1D and 3D ground response analyses are performed with several long-return period motions. The modeling results would be compared to identify the conditions under which the 3D analysis results are significantly different.