Evaluation of seismic site response and development of site-specific surface response spectra has evolved in recent years through the use of both equivalent linear (EQL) and nonlinear (NL) computer codes. Before the nonlinear computer codes become popular among practitioners, equivalent linear site response analysis programs were used to develop site-specific design spectra for both soft and stiff sites. Nonlinear site response analysis is now used more routinely for projects planned on Site Class F sites. This paper presents the results of seismic response analyses completed for a Site Class F site at Grays Harbor, Washington. Both the equivalent linear (SHAKE2000) and nonlinear (D-MOD2000) computer codes were used to evaluate the site response under the maximum considered earthquake (MCE) using the guidelines set forth in 2006 International Building Code (IBC) and American Society of Civil Engineers (ASCE) 7-05 code. Comparison of surface response spectra, soil shear stress and strain at various soil layers computed using both the equivalent linear and nonlinear computer program. Conclusions regarding the limitations of the equivalent linear code and presents recommendations on the use of the nonlinear computer code in site response analysis for practitioners
