Seismic fragility assessment of large-scale pile-supported wharf structures considering soil-pile interaction

Seismic fragility curves are recognized as a useful tool for seismic performance assessment of pile-supported wharf structure (PSWS) exposed to seismic hazards. These curves quantify the probability of structural vulnerability against given ground motion parameters. Soil-pile interaction (SPI) is found to have a significant impact on seismic performance of pile-supported structures. In this study, in order to better understand the SPI effect, the seismic fragility of a large-scale PSWS located at the Port of Los Angeles Berth 100, USA, is fully investigated with and without considering SPI. Herein, the pushover analysis scheme is used for inferring the bound limits of seismic demands of this large-scale PSWS. Specifically, the purpose of pushover analysis is twofold: to identify which pile of the PSWS most likely suffers from seismic failure; and to determine the bound limits of seismic demands for estimation of fragility curves using the identified pile. A collection of ground motions with low and high moment magnitudes as well as small and large fault distances are selected for nonlinear time history analysis. The seismic demand models can be readily estimated from the data set of the intensity measure-seismic demand pairs by classical regression fitting. A comparison of fragility curves with and without SPI shows that SPI significantly influences the seismic fragility of the PSWS. For distinct damage states, the effect of SPI on the seismic fragilities of different piles can be totally different.