SOIL-STRUCTURE INTERACTION (SSI) EFFECTS ON THE SEISMIC RESPONSE OF DAMS

Abstract

The influence of Soil-Structure Interaction (SSI) is an important aspect to account for cases where two different materials are interacting. This aspect is prevalent in the case of foundations, concrete gravity dams and any embedded structures in the soil material. The seismic response of a concrete gravity dam is significantly affected by the interaction between the dam structure and the foundation bedrock. Finite Element analysis has been widely used to model seismic response and soil-structure interaction (SSI) effects of structures. The study discusses the seismic response and its impact on the SSI of a concrete gravity dam using Finite Element Analysis software, ABAQUS CAE. Further, the analysis has been carried out at standard static and dynamic loading conditions. Apart from gravity and hydrostatic loads, three natural seismic motions, Koyna, Kobe, and Northridge, are used to evaluate the response of the dam structure and its SSI. The hydrodynamic forces on the dam structure are modelled using Westergaard’s approach. In another approach, the reservoir body is modelled using water as a structure. The dam structure is placed over different bedrocks by using impedance ratio to assess the SSI effects, and the static and seismic response of the dam body is defined in terms of tensile stresses and displacement. Three natural seismic motions, Koyna, Kobe and Northridge, are used to study the influence of seismic motions on the hydrodynamic and SSI effects on the dam. The study highlights the importance of considering SSI effects under different loading conditions to design and analyse large dam structures.