Comparative Study of the Inelastic Seismic Demand of Eastern and Western Canadian Sites

The damage potential of earthquake ground motions compatible with site-specific 2% in 50 year uniform hazard spectra is compared at two North American sites in areas of moderate seismic hazard: Montreal, in the east, and Vancouver, along the west coast. For Vancouver, crustal, subcrustal and Cascadia subduction ground motion earthquake ensembles are considered. Nonlinear dynamic analyses of bi-linear single-degree-of-freedom oscillators exhibiting various ductility levels and damage laws were performed to determine R factors required to prevent structural collapse for each site and each system. Then, inelastic response parameters were computed for the general design case, wherein a prescribed R factor is used for a given system irrespective of tectonic region or structural period. The results show that the R factors vary with the ductility level, the damage law, the structural period, and the tectonic region. Neglecting the latter two dependencies in design, as is current practice, may lead to significant discrepancies in the level of protection achieved for different structures in different regions.