Seismic performance of a pile-supported wharf: Three-dimensional finite element simulation

Abstract

6Considerable three-dimensional (3D) effects are involved in the seismic performance of pile-7 supported wharves. Such effects include the pile-to-pile interaction mechanisms as dictated by 8 the behavior of the surrounding soil. This interaction might be further affected by potential 9 ground slope settlement/heave, and the constraint of pile connectivity along the relatively rigid 10 wharf deck. In order to capture a number of these salient response characteristics, a 3D finite 11 element (FE) study is conducted herein. The prototype system motivating this study is presented, 12 along with the corresponding numerical details. A realistic multi-layer soil profile is considered, 13 with interbedded relatively soft/stiff strata. Effect of the resulting seismically-induced ground 14 deformation on the pile-supported wharf system is explored. Specific attention is drawn to the 15 noteworthy potential changes in axial force due to variation in pile embedment depth, and the 16 ground slope deformation. The analysis technique as well as the derived insights are of 17 significance to general pile-wharf-ground system configurations. 18 19 Arulmoli et al. (2004) carried out a 2D dynamic finite element (FE) DYNAFLOW analysis of a 43 wharf-dike-backland system, investigating the pile pinning effects. Using OpenSees, Yang et al. 44 (2012) conducted 2D FE simulations to develop fragility curves for a typical wharf structure. 45 Employing advanced structural and soil modeling procedures, Shafieezadeh et al. (2012a) 46 performed 2D nonlinear plane-strain seismic analyses. The simulated results showed that the 47

Aspects of bridge‐ground seismic response and liquefaction‐induced deformations

“…The Open System for Earthquake Engineering Simulation (OpenSees, http://opensees.berkeley.edu) framework was employed to conduct the nonlinear bridge‐ground system analyses subjected to seismic excitation. OpenSees is developed by the Pacific Earthquake Engineering Research (PEER) Center and is widely used for simulation of geotechnical systems and soil‐structure interaction applications . The OpenSees elements and materials used in this FE model are briefly described below.…”

“…The equation is solved using the modified Newton‐Raphson approach with Krylov subspace acceleration . A relatively low level of stiffness proportional viscous damping was used to enhance numerical stability (coefficient = 0.003), with the main damping emanating from the soil nonlinear shear stress‐strain hysteresis response …”

“…The zerolength and zerolengthSection elements are employed to axially connect the rigid links to adjacent soil nodes and provide yield shear force in each link according to the soil‐pile interface friction angle and adhesion. As such, the yield shear force is limited by F = ( c A + σ′ tanδ)·l·h/N , where l is the perimeter of the pile, h is center to center contributing height (according to the adjacent soil element heights), c A is the soil‐pile adhesion, δ is the soil‐pile friction angle, σ′ is the lateral effective stress, and N is the number of zeroLengthSection elements along the pile perimeter …”

“…In the transverse direction, a representative 2.0‐m‐wide slice (Figure A) was taken to account for the bridge's geometric configuration . On this basis, a 3D bridge‐ground FE mesh is developed (Figure ).…”

“…Based on the above, the FE mesh for the bridge‐ground model (Figure A) was generated comprising 22 050 nodes, 17 415 brick elements, 464 nonlinear and 90 linear elastic beam‐column elements, 1856 rigid beam‐column links, 1856 zerolength elements, and 1856 zerolengthSection elements. Along both the West and East side mesh boundaries (Figure ), soil columns of large size (not shown) are included . These soil columns, at an adequate distance (around 100 m) away from the bridge structure to minimize boundary effects, efficiently reproduce the desired free‐field response at these locations.…”