Three-Dimensional Wharf Response to Far-Field and Impulsive Near-Field Ground Motions in Liquefiable Soils

Abstract

Seismic performance evaluation of wharf structures constitutes the core of the vulnerability assessment of seaport infrastructure exposed to seismic events. Because this performance will depend on complex interactions between the surrounding potentially liquefiable soils and wharf foundation and structure, detailed and careful implementation of advanced modeling techniques is needed. These models are required to capture such highly nonlinear phenomena as permanent seaward deformation of embankment soils, soil-structure interaction in liquefiable soils, spread of plasticity in prestressed piles, and force-deformation of pile-deck connections. This study utilizes such modeling approaches to investigate the three-dimensional (3D) nonlinear response of a typical pile-supported container wharf structure in liquefiable embankment soils. Input excitations for this analysis consist of embankment soil deformations for a far-field and an impulsive near-field ground motion. These excitations are derived using two-dimensional (2D) plane strain free-filed analyses for transverse (seaward-landward) and vertical directions and a spectral matching technique for the longitudinal (parallel to shoreline) direction. Results of these 3D analyses show that the oscillating component of embankment deformations is the primary contributor to the maximum response of the piles sections and pile-deck connections, and that effects of permanent deformations of the embankment soil are much smaller. The analysis results also demonstrate the importance of the structure’s 3D response characteristics, including longitudinal and torsional responses of the structure that are comparable to the transverse wharf responses during large amplitude oscillating embankment deformations owing to impulsive near-field motions. These important 3D response characteristics are not captured by more typical 2D wharf response analyses. Detailed comparisons of the responses of the 3D wharf model to corresponding responses from the 2D model of the wharf are provided.