Continuum soil-structure-interaction model of the LHPOST6 shaking table reaction mass at UC San Diego

The recently upgraded six Degree-of-Freedom Shaking Table, LHPOST6, at UC San Diego, underwent a series of forced vibration tests to evaluate the post-upgrade dynamic response of the foundation-soil system. The resulting data were instrumental in obtaining frequency response curves of the system, which were used to determine its low-strain natural frequencies, effective viscous damping ratios, and reaction mass displacements. The extensive experimental data motivated the creation of a detailed Soil-Structure-Interaction model of the reaction mass-soil system. The structure and soil were modeled using 3D Finite Elements in STKO-OpenSees and calibrated with the acquired data via a parametric study. The 3D continuum FE model and the calibration procedure based on a single soil parameter (shear wave velocity profile) proved to be an effective tool to reproduce the experimental results accurately. This paper describes the Finite Element model, its calibration, and validation. In addition, the paper provides suggestions to simplify continuum models and promote their use in professional practice. The objectives of this campaign, alongside the growing accessibility of high-performance computing, may serve as a step toward using SSI continuum models in the industry.