The Willingdon Avenue Overpass crosses the Burlington Northern rail tracks and two roadways approximately half a kilometre north of the Trans-Canada Highway. Constructed in 1967, the 75 metre-long, three-span bridge carries six lanes of traffic along an important traffic artery and designated disaster response route. The overpass consists of ten, three-span, continuous pre-stressed concrete I girders, with a continuous concrete deck slab; and a substructure consisting of cast-in-place abutments and two inclined precast column piers, founded on spread footings. Both abutments are seated on fill retained by concrete retaining walls. The inclined pier columns are pinned at either end and provide little or no lateral restraint to the bridge.
The City of Burnaby retained Associated Engineering to complete a seismic evaluation and design of seismic upgrades.The assessment of the bridge identified several seismic vulnerabilities, including insufficient abutment wall strength, inadequate girder seat lengths and shear keys at girder ends, and deficient connections between the precast columns and girders. The seismic retrofit scheme consisted of soil anchors at both abutments to stabilize the abutment retaining walls; concrete shear blocks at the north abutment to prevent transverse sliding of the abutment; shear keys between the precast girders at each abutment; and column restrainers at each girder–column connection.
Following design, Associated Engineering provided contract administration and construction inspection services for the $0.5 million seismic retrofit construction contract.