SEISMIC UPGRADE OF BC HOUSING'S 20 STOREY NICHOLSONTOWER IN VANCOUVER, CANADA

摘要

BC Housing manages an extensive inventory of subsidized housing mostly in the Vancouver area. Theyhave undertaken a program to carry out seismic retrofitting of key aging facilities that have high tenantoccupancy and have been determined to have a high risk of severe damage or collapse for the codespecified earthquake. Design of seismic retrofitting of a permanently occupied residential tower is achallenge that must balance cost, maintain fire safety and minimize disruption to the tenants.This paper presents the retrofit design of a 20 storey concrete tower in Vancouver's 'West End', an areaof dense high rise construction. The concrete shear wall structure was originally constructed in 1969 andhouses some 250 tenants. The initial three-dimensional response spectra analysis, using both SAP2000and ETABS software, determined the load distribution to the existing non-ductile structural componentsand the capability of the existing structural system to contribute to the final retrofit structural system.The retrofit solution included the construction of external concrete shear walls up to the 17th floor, alongwith associated foundation requirements both external to the building and within the basement andstrengthening of the buildings two internal stairwells using continuous steel plates. A key aspect of theretrofit was the continuous vertical sawcutting of the concrete core within the elevator shaft to modify thestiffness in a manner that best suited the overall structural response.Making provision for adequate fire exiting during construction was key. This and other lessons learnedduring the construction period are also presented in this paper with conclusions regarding theeffectiveness of the various aspects of the retrofit with respect to tenant disruption and constructability.