Response Spectrum Analysis of Concrete Gravity Dams Including Dam-Water-Foundation Interaction

A response spectrum analysis (RSA) procedure, which estimates the peak response directly from the earthquake design spectrum, is available for the preliminary phase of design and safety evaluation of concrete gravity dams. This analysis procedure includes the effects of dam-water foundation interaction, known to be important in the earthquake response of dams. This paper presents a comprehensive evaluation of the accuracy of this RSA procedure by comparing its results with those obtained from response history analysis (RHA) of the dam modeled as a finite-element system, including dam-water-foundation interaction. The earthquake response of an actual dam to an ensemble of 58 ground motions, selected and scaled to be consistent with a target spectrum determined from a probabilistic seismic hazard analysis for the dam site, was determined by the RHA procedure. The median of the peak responses of the dam to 58 ground motions provided the benchmark result. The peak response was also estimated by the RSA procedure directly from the median response spectrum. Comparison of the two sets of results demonstrated that the RSA procedure estimates stresses to a degree of accuracy that is satisfactory for the preliminary phase in the design of new dams and in the safety evaluation of existing dams. The level of accuracy achieved in the RSA procedure is noteworthy, especially considering the complicated effects of dam-water-foundation interaction and reservoir bottom absorption on the dynamics of the system, and the number of approximations necessary to develop the procedure. (C) 2014 American Society of Civil Engineers.