Effects of Joint-Movement on the Earthquake Response of Arch Dams

Abstract eng:
The earthquake observation at Pacoima arch dam revealed that during very strong earthquakes joint movement (joint opening in the normal direction and slippage along tangential direction) can take place. The weakening of dam integrity and possible damage to joint waterstops raised a safety concern to engineers. This is a kind of frictional contact problems characterized by highly nonlinear nature. In the conventional approach, an idealization of flat joint is assumed to simplify the solution, joint movement in the tangential direction is restricted to take into consideration the effect of shear keys. In order to obtain a better understanding of joint-movement phenomenon, three joint models were studied: (1) flat joints where free opening in the normal direction and free sliding in the tangential direction were allowed; (2) flat joints, only opening in the normal direction was allowed; (3) joints with a simplified shear keys. In this paper, a Nonlinear Non-Smooth Equation method with property of guaranteed convergence is employed to solve the frictional contact problems. Moreover, an implicit-explicit time integration scheme is employed to analyze the dynamic response of dam-foundation system subjected to earthquake excitation. The dynamic analysis of an arch dam with the first two joint models is performed by the proposed analysis approaches. And earthquake responses of the arch dam with rigid base for all three joint models are also analyzed by ANSYS. It was found, the stress distribution and joint openings of the first model is even more approaching those of the third model, because in the model of joints with shear keys, movement in the tangential direction may take place to some extent.

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