The Investigation Of Dam Foundation Interaction Considering The Effect Of Foundation Mass

Dams as one of the most important and massive engineering structures demand more attention due to their complex analysis. The enormous dimension of the dam and its interaction with the foundation and reservoir domain make it difficult to fully consider all analytical aspects. In order to study the whole system, researchers usually try to develop simplifying methods to consider the real conditions of dam-reservoir-foundation systems. The obtained results in recent years have indicated that the proposed methods are complicated and time consuming. Considering these limitations, design codes usually propose some simple assumptions for analysis, especially for the initial study phases. However, the implication of these primary methods may lead to overestimated responses that are usually conservative. The massless foundation is one of the most important simplifying assumptions in the analysis process of the dam-reservoir-foundation system, which has been considered broadly by dam designers based on its simple application. However, the obtained results during recent years have indicated that the massed foundation assumption has profound effects on structure dynamic responses and should be considered in the analyses. In this study, the far-end boundary condition of foundation (Lysmer Boundary Condition) and semi-infinite element for the foundation have been investigated for the analysis of the dam-reservoir-foundation system. In the proposed method, although the mass of foundation has been considered, the seismic load would be imposed on dam body of concrete gravity dam. The analyses have been carried out under different time histories including broadband of Peak Ground Acceleration (PGA). The dam responses due to massless foundation assumption have been investigated for comparison. The comparison of the obtained results and those of the traditional method clearly indicates the capability and efficiency of the proposed method. Furthermore, the far-end boundary condition of foundation and semi-infinite elements considerably reduced the time and cost of the analysis; therefore, these could be practical approaches to preliminary analyses that might be useful for engineers and researchers.