Response of an Earth Dam to Spatially Varying Earthquake Ground Motion

The stochastic response of the Santa Felicia earth dam, in southern California, to spatially varying earthquake ground motion (SVEGM) is analyzed. An SVEGM model that accounts for both incoherence and propagation of seismic waves is used, the results are compared with those for various simplified excitations, and the sensitivity of the responses to coherency models proposed by different researchers is investigated. A 3D inhomogeneous finite-element model is used to represent the dam. Finite element-based random vibration analysis is performed and the statistical moments of Cartesian displacement, stress, and strain responses are computed. Statistical moments of the maximum shear stress are computed using Monte Carlo simulation that utilizes results from the random vibration analysis. The results indicate that the stress response of stiff material near the base of the dam can be significantly increased due to SVEGM, and that the increase is sensitive to the low-frequency variation of ground motion coherency.