UC San Diego

Soil-structure interaction (SSI) corresponds to the phenomenon that occurs when seismic waves coming from the soil affect the response of a structure and then, the response of the structure affects the response of the soil. It is often thought that the soil-structure interaction is beneficial for the behavior of the structure since it increases the period of the structure and incorporates additional damping due to the radiation of energy into the soil. For this reason, in practice, SSI is either not included when modeling the structure or is replaced by increased viscous damping.

In models developed to perform nonlinear time-history analyses of 3D structures, the soil nonlinearity and radiation damping are often represented by a series of springs and dashpots placed along the height of the piles in two orthogonal directions. This thesis shows that such array results in bias in the response, and an improved array of the p-y springs is discussed.

A case study performed on a typical Chilean mid-rise building founded on piles is presented. To compare the effects of SSI on the building's response, nonlinear fixed-base and on pile models were developed in ETABS 20 and subjected to the strong input ground motion recorded during the 27 February 2010 Mw 8.8 Maule earthquake. The SSI effects resulted in a slight increase in demands of key engineering response parameters, but the increase did not justify the incorporation of SSI in the analysis.