Abstract: Water compressibility and dam-water dynamic interaction are important factors that affect the hydrodynamic pressure on dam surface and the dynamic characteristics of an arch dam. This study develops a finite element model of the arch dam-foundation-reservoir water system to evaluate the effects of reservoir water on arch dam dynamic characteristics through a case study of the Laxiwa arch dam. In analysis, we use two reservoir water models, a Westergaard added mass model and a fluid-structure coupling model; three conditions are examined of Westergaard added mass, structure coupling with incompressible water, and structure coupling with compressible water. Results show that water storage behind an arch dam reduces its natural frequencies; compressibility of the water reduces them further, thereby changing its vibration modes. The results help improve the accuracy of high arch dam analysis and seismic response analysis.

Key words: high arch dam, dynamic characteristics, fluid-structure coupling, added mass, water compressibility, finite element