When a project in Vancouver triggers NBCC 2020 seismic requirements, base isolation isn't just an option, it's often the most rational path. The city sits less than 300 km from the Cascadia subduction zone, and the Georgia Basin's deep soil deposits amplify long-period ground motion in ways that conventional fixed-base design struggles to handle. Our lab team works directly with structural engineers to characterize the site-specific spectra that isolation systems must accommodate, running dynamic soil tests that feed into the nonlinear time-history models. Before finalizing isolator parameters, a solid understanding of the subsurface profile is essential, which is why many projects start with a MASW survey to map shear wave velocities down to bedrock and confirm the Vs30 classification for the NBCC site class. We also see cases where liquefiable layers need to be ruled out early, and that's where a liquefaction assessment becomes part of the conversation before the isolation design advances.
A properly tuned base isolation system shifts the structure's fundamental period away from the 1 to 2 second range where Cascadia energy peaks, reducing seismic forces by 60 to 80 percent.
