Impact of vertical ground motions on base isolation seismic upgrade of the Canadian parliament building

By By Armin Bebamzadeh (Ausenco), John Sherstobitoff (Ausenco), Dan Carson (WSP), David Arnold (WSP), Ian Aiken (Seismic Isolation Engineering Inc.), Cameron Black (Seismic Isolation Engineering Inc.), Mason Walters (Forell/Elsesser Engineers Inc.), Ali Roufegarinejad (Forell/Elsesser Engineers Inc.), Tuna Onur (Onur Seemann Consulting, Inc.)

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The Centre Block of Canada's Parliament, a prominent and iconic heritage building, is currently undergoing an extensive restoration. Constructed over a century ago, Centre Block consists of a six-story structure with predominantly stone and brick walls, steel columns, and unreinforced concrete wall foundations, connected to a 92 m tall Peace Tower supported by unreinforced concrete piers, both of which are at high seismic risk. Base isolation is being implemented for the seismic upgrade of Centre Block as a cost-effective retrofit method to reduce the seismic demand, enhance likelihood of achieving business continuity, and preserve the heritage characteristics of the building. The base isolation system comprises approximately 580 different types of isolators including rubber and flat slide bearings.

This paper investigates the impact of the vertical component of ground motions on the shear demands of superstructure walls and piers in a base-isolated structure. The results highlight a significant increase in shear demands for the superstructure walls due to the vertical component of short-period ground motions, a response not necessarily attenuated by the isolation system. However, despite this increase, the analysis demonstrates that the base-isolation system effectively reduces the induced base shear in the walls compared to conventional retrofit methods for fixed base structures.

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