Frequency Domain Spectral Analysis of Arch Dams under Random Seismic Excitation

Abstract

Previous research on seismic response analysis of dams primarily treated earthquakes as deterministic events; only a few studies on arch dams have explored earthquakes as random processes. This study introduces a three-dimensional seismic analysis of the Morrow Point arch dam, considering fully correlated random ground motion. The random ground excitation is characterized by the power spectral density function (PSDF) of the Kern County earthquake, for which the response time history is available. The spectral analysis technique describes the PSDF of the dam’s response using the desired transfer function derived from Abaqus software. The analysis method is similar to that employed in finding the PSDF of the response of offshore structures from a given wave spectrum (PSDF). The method is validated by confirming the results of the proposed method with those of modal spectral analysis for empty dams and those of the time history analysis of the full reservoir dam. The results from the numerical study show that (1) the PSDF of responses obtained by modal spectral analysis using the first ten modes of the dam matches with those obtained by the direct analysis using transfer functions for the empty dam; and (2) mean peak arch stresses increases along the height of the dam from base to top, whereas mean peak cantilever stresses decreases; further, the mean peak arch stresses are less than the mean peak cantilever stresses at the base.