Application of Simplified Kinematic Soil-Structure Interaction Procedures to Validate Finite Element Models of Buildings with Large Foundations

Variations between foundation-level and free-field ground motions can be mainly attributed to the kinematic soil-structure-interaction (SSI) effects. Current design guidelines such as ASCE 41-17 include a simplified procedure to estimate the kinematic SSI effects for regular-sized buildings with footprint sizes less than 260 ft and embedment depth shallower than 20 ft. Therefore, modifying such equations for the design of buildings with large foundations and embedment depths is of great importance, especially when safety-critical structures are involved. A recent study at the University of Nevada, Reno (UNR) has recently proposed modifications to the ASCE 41-17 equations taking into account the unique features of such buildings using a data set of earthquake motions recorded at five instrumented sites in Japan. The finite element method (FEM) is an efficient numerical tool to take the kinematic SSI effects into account. However, in engineering practice, it is often the case that the actual recordings at the location of the site are not available to validate the FE models against. This study benchmarks the results of the FEM, the simplified code-based formulations, and the modified simplified equations against the actual recordings to show the suitability of the modified simplified equations for validating the developed FEM models. For this purpose, a three-dimensional (3D), nonlinear (NL) SSI model of a well-instrumented site located in Japan, including a building with a large foundation and embedment depth, is developed in the time-domain code LS-DYNA. Both low-intensity and design-level records from the recordings at the site are applied to the model. It is demonstrated that the FEM captures the kinematic SSI effects appropriately. It is also shown that the modified simplified equations show good agreement with the results captured via FEM. It is recommended that for buildings with large footprints and embedment depths, the modified simplified equations are used instead of current simplified procedures to validate the SSI models in case the actual recordings are not available for validation purposes.