Study on Evaluation Method for Seismic Safety of Multiple Arch Dam

Multiple arch dam is complex structure composed of more than two arch dams. There are several construction cases of multiple arch dam in the world, which were constructed about several decades ago. As for such aged dams with peculiar figures, earthquake resistant design based on dynamic analysis was not executed from the limitation of technical levels at the time of construction, so re-evaluation of seismic safety shall be necessary based on the latest technical standards.

In this study, I made comparative analyses by three-dimensional dynamic analysis for the purpose of improving accuracy and reliability of seismic safety evaluation of multiple arch dam. I set two kinds of analysis model. One is individual dam model, or single dam model. Another is compound dam model, or double dam model.

As a result of comparative analyses, dynamic tensile stress evaluated by the single dam model became smaller than that evaluated by the double dam model. So, it is considered that the evaluation by the single dam model will be dangerous side compared with that by the double dam model. This tendency increased as values of dynamic shear modulus of dam decreased.

Finally, it was concluded that the mutual dynamic effects among plural arch dams should be taken into account in order to realize an accurate and reliable evaluation for seismic safety of multiple arch dam.