Ground response analysis using non-recursive matrix implementation of hybrid frequency-time domain (HFTD) approach

This paper presents formulation of a Hybrid Frequency-Time Domain (HFTD) method for the solution of nonlinear ground response problem. Using non-recursive matrix approach, the displacements, caused by the bedrock acceleration, at the surface of layered soil are calculated while pseudo-forces due to nonlinear behavior of soil are obtained iteratively using an appropriate transformation scheme. The analysis process is continued until the pseudo-forces reach negligible values. Two different ground motions recorded at Gilroy 2 reference site during the Loma Prieta earthquake of 17 October 1989 and Coyote Lake earthquake of 6 August 1979 are analyzed using proposed method. The results are in good agreement compared to field observations. Furthermore, the two input motions are analyzed with SHAKE (Equivalent Linear Method) and NERA (Non-linear Method) programs and it is shown that the proposed method provides better predictions when compared with the field observations.