The Importance of Site-Specific Seismic Nonlinear Ground Analysis in Eastern Canada

ABSTRACT: In the current state of practice in Eastern Canada, the seismic hazard at a site is defined by the Geological Survey of Canada with a uniform hazard spectrum (UHS) for a site of class C, and modified using the site amplification factors recommended by the National Building Code of 2015 (NBCC 2015) or the Canadian Highway Bridge Design Code (S6-19). When necessary, site-specific ground response analysis are performed using equivalent linear ground response analysis, which considers an unrealistic assumption of constant dynamic properties during wave propagation. In this study, for a wide variety of soil sites in Quebec, dynamic simulations were conducted using the software DEEPSOIL to compute site-specific soil amplification factors. The site amplification factors from the NBCC 2015 and those computed using nonlinear 1D ground response analysis are then compared, and the results indicate larger amplification of the earthquake response spectrum around the site’s natural period (or at periods slightly longer than the natural period) than the one calculated with the NBCC 2015 recommendations. Therefore, the NBCC 2015 may not always be conservative and could underestimate the seismic demand at a site.