The Effect of Spatially Varying Earthquake Input Motion on Earth Dams with Various Dimensions

Seismic behavior of earth dams is significantly influenced by the nature of input motion. The implementation of identical motions at the base of the dams can yield unconservative dynamic responses. Therefore, spatially varying earthquake ground motion (SVEGM) should be considered in their seismic response analysis and design. This paper presents the nonlinear seismic analyses of earth dams subjected to SVEGM using finite difference method. Different models of earth dams are considered for this purpose. These models are different in dam height and foundation length.Different methods are available for the generation of SVEGM. A computer software is used for conditional generation of SVEGM input motion. For unconditional case, SVEGM is generated by a computer code developed in the present research based on spectral-representation-based technique. Two different coherency models are used for the generation of SVEGM. Results are expressed in terms of peak accelerations along the dam height and horizontal and vertical displacements of dam crest. The results indicate that generally the uniform input motions can produce higher values of peak accelerations along dam height and dam crest horizontal displacement than SVEGM excitation. However, the crest vertical displacement of smallest dam obtained by SVEGM input analysis is higher than that calculated by using uniform input analysis.

Keywords:

SVEGM , Earth dam , Coherency model , Conditional and unconditional simulation methods , Dynamic Analysis