Page - 1475 - in Book of Full Papers - Symposium Hydro Engineering

impounded water and flexible foundation rock, to the transverse (horizontal) and vertical components of earthquake ground motion. Fenves and Chopra (1984) developed a semi analytical- numerical procedure to analyze the earthquake response of concrete gravity dams. Effect of reservoir-foundation interaction was the subject of a study conducted by Dominguez et al (1990). A boundary integral technique was proposed for the investigation of the response of dam-reservoir- sediment-foundation systems subjected to ground acceleration. Bougacha et al. (1993) introduced a technique based on the Finite Element Method for the analysis of wave generation in a layered, fluid filled poro-elastic media to consider the sediments. Bhattacharjee and Leger (1994) conducted a study on the two dimensional static fracture behavior of dams. Smeared crack models were developed from a nonlinear fracture mechanics point of view that can simulate the tensile and shear softening of the plain concrete. The static fracture behavior of a dam subjected to an incremental increase of the reservoir water level was also investigated by Bhattacharjee et al. (1995). A rotating smeared crack model was considered in the nonlinear finite element analyses. The uplift pressure occurring inside the smeared crack bands was taken into account by effective porosity concept. Ghanaat (2004) introduced an assessment approach that utilized linear time history analyses. The potential failure mechanisms of concrete gravity, buttress and arch dams were discussed and taken into consideration at the performance evaluation approach. Javanmardi et al. (2005) developed a theoretical method to determine the water pressure variations along a tensile crack during dynamic response. The results of the proposed model were compared with experimental test results. Arabshahi and Lotfi (2008) conducted a study on the natural vibration mechanisms due to damage at the dam foundation interface. Zeidan (2013) used ANSYS code to investigate the interaction of reservoir water-dam structure. Yucel (2013) evaluated the hydrodynamic pressures, dam-reservoir- foundation rock interactions and reservoir bottom absorption. Zeidan (2014) analyzed the problem of dam-reservoir-foundation seismic response on concrete gravity dams numerically using ANSYS code. Her results showed that simulation of foundation in dam-reservoir interaction problems significantly affects the seismic response of concrete gravity dams especially in case of mass rock foundation. Although the dam-reservoir-foundation interaction has been highlighted via many authors, the dam-reservoir-foundation coupled system is a very complicated phenomena and further studies on foundation simulation on seismic response of concrete gravity dams including foundation-structure interaction is required. The objective of the present study is to assess the impact of key parameters which affect the static and dynamic behavior of concrete gravity dams. A 2-D Finite Element model is employed using ANSYS program. KOYNA dam subjected to the S00E component of EL-Centro earthquake is investigated as a typical case of study. The dam is represented as a finite element system, the fluid domain, as a continuum of infinite length in the upstream direction and the foundation rock region as a viscoelastic half-plane. Static, modal and time history analyses are considered in the dynamic simulation. In the static and dynamic analyses, the foundation is simulated considering foundation flexibility. The dam concrete, foundation rock and reservoir water are assumed to have homogeneous, isotropic, linear and elastic properties. Reservoir water is assumed to be incompressible and inviscous fluid. The dam-reservoir-foundation coupled system is idealized as shown in Figure 1. Governing Equations and Boundary Condtions Governing equation of wave propagation through fluid is represented in both the Eulerian and Lagrangian methods. The governing fluid-structure system equation is solved using wave propagation through the fluid by assuming linear compressibility and inviscousity. The wave propagation equation through acoustic fluid is as follows (Chopra and Chakrabarti 1981): 1475