Physical and numerical simulations of soil-structure interaction
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For the seismic performance assessment of new and retrofit structures it is important to consider the effects of soil-structure interaction. Several numerical methods of varying complexity and accuracy have been used to evaluate these effects in practice, including the numerical programs, SHAKE and SASSI, which perform ground response analysis using an equivalent linear method, and soil-structure interaction analysis using a frequency-domain substructuring method, respectively. This study involves the assessment of these programs using a database of building responses recorded from a centrifuge test performed at the NEES@UCDavis centrifuge facility, as a part of the NEES City Block project. The centrifuge test involves shaking of two isolated, small-scale building models placed on dry Nevada sand, whose counterparts at the prototype scale are representative of typical low- to medium-rise SMRF buildings situated in downtown Los Angeles. Seventeen ground motions with increasing damage potential are applied to the models. Three of these seventeen excitations are simulated using the programs SHAKE and SASSI to calculate the free-field response of the soil, and the response of the soil-structure systems, respectively. These three ground motions include a low, medium and high intensity motion. Soil-structure interaction effects are calculated from the responses, and a comparison is made between the numerical results and experimental observations. The numerical predictions for the low intensity motion are good. For the higher intensity motions, the nonlinear response of both the soil and the structures was only captured approximately. SSI calculations are also carried out using the simplified procedures of ASCE 7-10 and FEMA 440, and results are compared with the experimental observations.