1. Single-Frequency Method for Computing Seismic Earth Pressures

Seismic earth pressures computed using an elastodynamic Winkler solution that considers soil–structure interaction effects were recently developed by the authors using two different analysis approaches: a frequency-domain method in which ground motion time series are utilized to represent seismic demand and a single-frequency solution in which the ground motion is modeled using a single representative surface displacement and frequency. This paper provides guidance on selection of appropriate surface displacement and frequency for the single-frequency method to provide reasonable agreement with the frequency-domain solution. Suites of frequency-domains solutions are first performed, and peak seismic increment earth pressure resultants are computed. Single-frequency solutions are then performed by setting the frequency to the inverse of the mean period of the ground motion and selecting the surface displacement amplitude required to match the seismic increment resultant from the frequency-domain solution. Regression equations are provided to define the surface displacement amplitude as a function of peak ground velocity and mean frequency.