Westshore Terminals Overpass

Working closely with a geotechnical consultant, Associated Engineering’s designers determined that the most economical approach to bridging on the marine fill site was a series of lightweight simple spans on single-column piers and low-bearing pressure footings, occupying the same footprint as the existing bridge.  Four 30 metre spans were selected to cross the two rail tracks and access roads, with the earthfill approaches retained with mechanically stabilized earth walls. The selected scheme was chosen for its ability to accommodate future predicted ground deformations.

A major consideration was accommodating the 1 in 2475-year earthquake ground motions for the Class F marine-fill site.  Drawing on its experience with cost-effective design of base-isolated bridges, Associated Engineering was able to solve this stringent design challenge by installing ‘link decks’ between the spans to create a continuous deck diaphragm and ‘tuning’ the isolators to suit the flexibility of each individual substructure component.  The isolators selected are simple elastomeric bearings vulcanized to plates bolted to both superstructure and substructure.