Comparison Study of One-Dimensional Site Response Analysis Methods

Abstract

The ground responses computed via frequency domain (FD) equivalent linear (EQL) and time domain (TD) nonlinear (NL) methods can considerably differ because of the constitutional differences in numerical approaches, damping formulations, and modeling of nonlinear soil response. To systematically evaluate the TD-NL and FD-EQL approaches, this study performs TD-NL, TD-EQL, and FD-EQL site response analyses considering different input motions, intensities of input motions, depths of soil columns, and nonlinear properties. Results show that the differences in the site responses calculated by the two approaches are highly influenced by dynamic soil properties, the significant nonlinearities of which (e.g., sand) tend to magnify such differences and the high damping of which tend to mitigate the differences. An amplification factor by TD-NL exhibits more nonlinearity than that by FD-EQL but agrees well with the nonlinearity in the 2015 NEHRP site factor, indicating that TD-NL is a better method than FD-EQL for modeling soil nonlinear behavior.