Rate and Frequency-Dependent Equivalent Linear Site Response Analysis Algorithms

Abstract

One-dimensional site response analysis is commonly performed to estimate the seismic site effects. Equivalent linear analysis, in spite of its inherent weaknesses, is predominantly used in engineering practice due to its simplicity and ease of use. This paper develops two distinct modifications of currently used equivalent linear algorithm, which are rate and frequency-dependent soil behavior modeling capabilities. Rate-dependent soil model is developed and implemented to mimic the influence of the rate of shearing on soil response. The frequency-dependent soil model is developed to better approximate the nonlinear soil behavior. In the model, the dependence of the shear strain on loading frequency is modeled. by incorporating the frequency dependence of the shear strain, which indicates that the high level of shear strain is associated with low frequency, while low strain typically occurs at high frequency. It is shown that the influence of the rate dependent soil behavior can be important in propagating weak ground motions through cohesive soil deposits. The frequency-dependent algorithm is not always successful, and further modifications and frequency dependent curves need to be developed.