Rate-dependence of rock ll behavior on propagated near fault ground motions

Equivalent linear one-dimensional site response analysis, which approximates nonlinear soil behavior within the linear analysis framework, is widely used in estimating local site eects. In this analysis, soil behavior is often assumed to be independent of the frequency of seismic loading. However, the large scale triaxial test results on rockll material have shown that the shear modulus and, especially, the damping ratio, are in uenced by the loading frequency. A series of one-dimensional equivalent linear analyses were performed on 30 m and 90 m thick proles of the studied rockll material to evaluate the frequency-dependent soil behavior under several well-known near-fault ground motions. The analyses are carried out for three base acceleration levels, namely, 0.1 g, 0.35 g and 1 g, using the simple time history scaling method. Results show that the frequency-dependent shear modulus and damping ratio can have a pronounced in uence on propagated ground motion. The frequency-dependent soil behavior is also dependent on the thickness of the soil prole, amplitude, equivalent no. of cycles at 0:65max, and frequency content of the input ground motion