Numerical Modeling of Soil-Shaft Interaction Validated Using the Instrumented Hayward Bridge in California-PPT Presentation

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This study presents a numerical approach for modeling soil–shaft interaction and evaluating seismic responses at the instrumented Hayward Bridge in California. The analysis was conducted in OpenSees in two stages: first, a free-field soil model was developed; then, its results were used as input for a soil–shaft interaction model.<br /><br />The 30 m soil profile consisted of 1 m of stiff black clay over 29 m of highly weathered, sheared gabbro. The free-field model used 90 four-node elements, a pressure-independent multi-yield soil model, hysteretic damping, and Lysmer–Kuhlemeyer boundary dashpots. It was subjected to bidirectional ground motions from the 2018 Berkeley and 2021 San Lorenzo earthquakes. The resulting soil displacements, accelerations, and spectral responses were examined.<br /><br />The interaction model represented a 12 m drilled shaft with a three-dimensional, six-degree-of-freedom elastic beam-column model. Free-field displacements drove the model, and p–y curves represented lateral soil resistance, with separate formulations for stiff clay and weak rock. The study evaluated shaft-head displacement, relative displacement, and soil reaction with depth.<br /><br />The results demonstrate the potential of numerical modeling to estimate soil responses at different depths even when direct acceleration recordings are unavailable, and to assess drilled-shaft behavior during earthquakes. The work supports improved understanding of how ground motions affect both soil layers and bridge foundations.

Keywords

soil-shaft interaction

seismic response

Hayward Bridge

OpenSees

free-field soil model

drilled shaft

p-y curves

ground motion

soil displacement

bridge foundation