Seismic Upgrading of the Mission Bridge

Abstract

The Mission Bridge is a key link and a lifeline structure in the high seismic zone of the Lower Mainland, British Columbia, Canada. The 1.1 km long bridge, built in 1973, was found to have several critical seismic vulnerabilities, as is typical for structures of its vintage. A comprehensive seismic assessment and retrofit design and construction program was carried out over 10 years to provide collapse prevention for the 475-year return period earthquake. The state-of-the-art assessment and retrofit was done using displacement-based methods. The main items of the retrofit were ground and foundation improvements, re-articulation of portions of the superstructure, addressing loss of span prevention, rehabilitation of deck joints, and enhancement of the ductility and shear strength of deficient concrete columns. The work incorporated innovative retrofit methods including making the steel box-girder in each main river span continuous, installing fibre-reinforced polymer jackets, improving deep soils / foundation performance, and the use of ultra-high performance fibre-reinforced concrete column jackets to provide column ductility against lateral spreading soil movements.