Year: 2025
Type: article
Abstract: A simplified approximate method to analyze the rocking response of pile groups subjected to seismic loading is introduced. The proposed method accounts for the nonlinear response of the soil and reinforced concrete (RC) piles, including the axial load dependency of RC bending moment capacity, and gapping effects at the soil–pile interface. The piles are replaced by an assembly of hysteretic (kinematic hardening) elements, combined with springs, sliders, and gap elements. Viscous damping is added to the springs and the hysteretic elements for the elastic range of the response. The proposed simplified method is verified against nonlinear three-dimensional (3D) finite-element (FE) analyses of a rocking 2×1 pile group in a stiff overconsolidated clay of uniform undrained shear strength. Two uniform shear strength profiles, Su=100 kPa (pile shaft adhesion factor α=0.75) and 220 kPa (α=0.25), and four cases of vertical loading are examined, ranging from vertical factor of safety FSV=10 (very lightly loaded), FSV=5 (lightly loaded), to FSV=3 (normally loaded), and to FSV=2 (heavily loaded). The moment-to-shear ratio is also explored, considering two different pier heights HP=6 and 12 m. The simplified method is shown to capture the seismic response of rocking pile groups remarkably well. The prediction errors of maximum foundation rocking and permanent settlement did not exceed 20% in most cases; the predictions of residual foundation rotations were less reliable. The proposed method neglects the contribution of the pile cap, cannot account for kinematic soil–pile interaction effects, and its applicability is limited to pile groups exhibiting rocking-dominated response. Furthermore, the method is intended for the seismic analysis of pile groups that fully mobilize their bearing capacity, and may not be equally efficient for pile groups that do not exhibit strongly nonlinear response. Focusing on cohesive soil, detailed calibration guidelines are proposed, well aligned with the existing literature and supplemented with a parametric FE study of a single pile in a soil of uniform shear strength. Although the proposed method offers considerable flexibility, further verification across different soil conditions and pile group typologies is needed. Additionally, extending the calibration guidelines to noncohesive soils would enhance the method’s applicability.
Authors: Max Sieber, Ioannis Anastasopoulos
Institution: ETH Zurich
Language: English
Subfield: Civil and Structural Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W4417181872