Analysis of Soil-Foundation-Structure Interaction During Earthquakes

The primary objectives of this study are to develop procedures and computer programs for determining the response of soil-foundation structure interaction systems during earthquakes as well as to investigate the nature of soil effect and the interaction effect. A two-dimensional analytical model consists of one-dimensional structural members, a two-dimensional rigid foundation block, and quadrilateral finite elements which idealize soil deposits. The soil is treated as either a linear elastic or an elastic-plastic material. Although engineers have recognized the complex behavior of soil-foundation-structure systems during ground shaking because of non-linear soil behavior and foundation embedment into the soil deposits, most interaction studies have relied on simple models.

Assuming the linear elastic stress-strain behavior of the soil a two-dimensional analytical model of soil-foundation-structure interaction is developed. The accuracy of the model is evaluated regarding the influences of artificial side boundary and finite element size. Parameter studies are performed for soil effects and interaciton effects, changing soil properties, soil depth, earthquake motions, structures and foundation embedment depth. A second analytical model is developed to incorporate the non-linear stress-strain behavior of the soil, i'.e. linear VB. elastic-plastic or equivalent linear VB. elastic-plastic, are investigated to determine the effect and significance of non-linear soil behavior.

 The parametric studies show that the existence of the foundation block considerably affects the response of the structure resting on the foundation and that the soil deposits play a key role in determining the magnitude and frequency characteristic of the response of soil-foundation structure systems. Realistic response predictions of structures during intensive bedrock shaking can be achieved only by non-linear analysis procedures. The overall studies show that the suggested analytical procedures are a promising approach for predicting the responses of soil and soil-foundation-structure system.