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UBC Theses and Dissertations

Georgia sedimentary basin effects on the response of modern tall RC shear wall buildings to M9 Cascadia subduction zone earthquakes Eksir Monfared, Alireza

Abstract

Tall residential RC shear wall buildings (RCSW) are predominant in Metro Vancouver. These buildings have the potential to experience large-magnitude earthquakes generated by the Cascadia Subduction Zone (CSZ). Furthermore, the region lies above the Georgia sedimentary basin, which can amplify the intensity of ground motions at medium-to-long periods and the resulting damage in tall structures. The goal of this thesis is to provide insights into the effects of the Georgia sedimentary basin amplification on: (i) spectral accelerations associated with M9 CSZ earthquakes, (ii) resulting force- and deformation-controlled actions in tall RCSW buildings, and (iii) ensuing earthquake induced repair costs and times. To this end, a suite of physics-based ground motion simulations of a range of M9 CSZ earthquake scenarios, which explicitly consider basin effects are used. These scenarios are benchmarked against a range of seismic hazard intensities, as defined in Canada’s 2015 National Seismic Hazard Model (NSHM), which neglects basin effects. Relevant ground motions are propagated through a suite of archetype RCSW buildings designed to comply with the requirements of the 2015 National Building Code of Canada (NBC) at eight locations throughout Metro Vancouver with distinct basin depths. Nonlinear dynamic analysis results under probabilistic seismic hazard estimates result in negligible collapse. However, collapse risk conditioned on the occurrence of the M9 motions results in probabilities as high as 15% at the deepest basin site. Additionally, seismic demands from the M9 simulations at deep basin sites result in earthquake-induced repair costs and times that exceed the 2475-year hazard level, far exceeding the ~500-year return period associated with large-magnitude CSZ earthquakes. Furthermore, the 2015 NSHM fails to capture the significant variability in seismic demands and resulting building performance observed across the Georgia sedimentary basin. Supplementary materials available at: http://hdl.handle.net/2429/77294.

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