Estimating Kinematic Demands From Lateral Ground Deformation on Pile-Supported Wharves-Paper

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The study evaluates a simplified method for estimating earthquake-induced lateral ground movements, or kinematic demands, on piles supporting wharves. Using data from a large-scale centrifuge test of a pile-supported wharf subjected to liquefaction, the authors assessed Newmark sliding-block analysis with pile-pinning effects incorporated using procedures developed for bridge foundations.<br /><br />The analysis iteratively combines three steps: estimate pile shear resistance using p-y analyses; include that resistance in a pseudo-static slope-stability analysis to determine yield acceleration; and calculate ground displacement using Newmark analysis. The resulting displacement profile is then used to update the pile analysis until the solution converges. Accelerations recorded within the failure mass were used to reduce uncertainty from site-response modeling.<br /><br />Including pile resistance substantially reduced estimated displacement compared with free-field estimates. For the test examined, the calculated median Newmark displacement was 7.3 cm, close to the measured permanent displacement of 9 cm. The median plus one standard deviation estimate was 10 cm and better matched the measured peak transient displacement of 12 cm. Analyses using accelerations at the model base underestimated displacement, while surface accelerations overestimated it.<br /><br />The findings support applying existing bridge-foundation pile-pinning methods to maritime structures such as wharves and piers. The authors recommend using median Newmark displacements to estimate permanent movement and median-plus-one-standard-deviation values for peak transient movement. They also emphasize selecting accelerations from within the failure mass and accounting for the foundation’s effective influence width. These conclusions are based on the tested conditions; uncertainty in soil accelerations and pore-pressure estimates was not evaluated.

Keywords

earthquake-induced ground movement

kinematic demands

pile-supported wharf

liquefaction

Newmark analysis

pile-pinning

lateral displacement

centrifuge test

pseudo-static slope stability

bridge foundations