Abstract
Many concrete arch dams passed nearly 50 years after construction. Because of growing public concern with stability at the time of a large earthquake, it is necessary to more rational seismic performance verification. Although model considering the bedrock is made in seismic performance verification, what it becomes difficult to extract natural modes of the dam body in case of considering the mass of the bedrock has been pointed out. And when carrying out seismic response analysis of civil engineer-ing structures built on bedrock spreading in semi-infinite like arch dam, we must set the appropriate boundary conditions be-tween analysis domain and free field. From the above, in this study, we have examined how to give the mass of rock when carrying out eigenvalue analysis and how to give boundary conditions to reproduce the actual phenomenon accurately when carrying out seismic response analysis.
