Input Motion Selection for Large-Scale Shake Table Tests to Evaluate Kinematic Soil–Structure Interaction Effects

This paper focuses on selecting input motions for a series of large-scale shake table tests planned at the University of Nevada, Reno, to experimentally investigate kinematic soil–structure interaction (SSI) effects in embedded foundations. Kinematic SSI results from wave scattering and foundation embedment, causing significant differences between foundation-level motions (FM) and free-field motions (FFM). While simplified procedures exist for incorporating kinematic SSI into design guidelines for buildings with small foundations and shallow embedment, their applicability to structures with larger footprints and deeper embedment remains uncertain. Experimental validation is essential for such cases, as kinematic SSI can reduce FM relative to FFM, potentially leading to cost savings in seismic design. This study aims to select input motions that capture a range of shaking intensities and frequency characteristics necessary to evaluate kinematic SSI effects under various seismic scenarios. To ensure a comprehensive range of shaking intensities, input motions were selected across multiple hazard levels. Unscaled ground motions for the Humboldt Bay Power Plant site in California were retrieved from the PEER NGA-West2 database using the conditional mean spectrum method and disaggregation results. These motions were then used to conduct nonlinear site response analysis (SRA) on a three-dimensional (3D) finite element model in LS-DYNA. The model included only the soil domain and embedded foundation, representing the interior of a laminar box setup, to simulate FFM and FM responses under the selected motions. The analyses provided insights into amplification factors and frequency-dependent variations, emphasizing how input motion characteristics influence foundation-level responses. Based on these findings, representative motions were identified for the planned large-scale shake table tests. This study presents a systematic framework for input motion selection in large-scale experimental evaluations of kinematic SSI effects. The chosen motions will provide key insights into kinematic SSI for large, embedded foundations, supporting the development of more effective seismic design strategies.