Comparison between the Effects of Near- and Far-Fault Ground Motions on the Seismic Response of a Soil-Pile-Structure System

Ground motions recorded in near-fault sites, where the rupture propagates toward the site, are significantly different from those observed in far-fault regions. In this research, finite element modeling is used to compare the effects of near- and far-fault ground motions on a system consisting of soil, pile group and structure, considering the possibility of non-linear behavior for the structure. The Von Wolffersdorff hypoplastic model with intergranular strain concept is applied for modeling of granular soil (sand). Five fault-normal near-fault ground motion records and five far-fault ground motion records, recorded on rock, are applied to the model. The results show that when seismic waves pass through the soil layer, the fundamental period of the soil layer lengthens, due to non-linear deformations. Also, in near-fault pulse-like ground motions a displacement pulse is generated in the pile response. Whereas, in the far-fault ground motions, due to the more uniform distribution of energy during the record, such pulse-like displacements are not observed in the pile response. Based on the obtained results, for a constant PGA, there are positive correlations between the values of maximum pile displacement, and PGD and PGV values of near-fault ground motion records. But such correlations are not observed in the case of far-fault ground motions.