A simplified model to estimate non-liquefiable NEHRP F site design spectra

The International Building Code requires a site-specific investigation for NEHRP F sites. However, established procedures for performing site-specific investigations of NEHRP F sites are limited. This study developed a simplified model to estimate design spectra for non-liquefiable NEHRP F sites to provide guidance for these cases. The model is based on the results of 4695 one-dimensional effective stress nonlinear site response analyses. It is intended to be used jointly with site-specific response analyses. The model is dependent on the period, design ground motion intensity, and site properties, and it characterizes the uncertainty of the estimate. The sensitivity of the results to reasonable variations in input parameters is investigated. The model is validated against field observations and compared with 80% NEHRP E site design spectra. The simplified model can capture the trends and magnitude of acceleration response spectra calculated from the site response analyses for all ground motions tested. Design spectra may fall below the 80% NEHRP E site design spectra for moderate to large levels of shaking intensity due to soil nonlinearity.