The Sheppard Subway bridge structure over the Don River in Toronto, Canada solves special geometric considerations and unusual structural loadings with a unique design approach. Owned by the Toronto Transit Commission (TTC), and designed by the consulting engineering company of McCormick Rankin Corporation (MRC), the Don River Bridge is certainly an innovative application of concrete technology.
The proposed new subway extension, running beneath Sheppard Avenue, posed a special problem at the intersection with Leslie Street—this point also happened to be where the Don River intersects Sheppard Avenue. In order to avoid the intersection and bridge abutments at the river crossing, the horizontal alignment of the underground subway was offset approximately 40 m, compelling the designers to create a unique, above-grade bridge to span the Don River. The design saved the TTC over $20 million. The resulting concrete structure typically has 3 m of freeboard, but severe regional storms raise the river to levels surpassing the top of the bridge, which places huge hydraulic forces on the structure—stream flows of up to 5.5 m/s. Of course the structure must also be watertight.
The single-span structure traverses approximately 60 m, is 5 m deep, and varies in width from about 15 to 18 m to account for the flared track alignment required at the adjacent Leslie Station platform. The 3-celled, prestressed, post-tensioned concrete box girder section houses EB and WB track and a center access-way. To verify the unique design, a 1:30 scale model was tested for the hydraulic loads.
The total project cost $932 million and includes approximately 6.4 km of subway and five new stations. Construction costs for the bridge alone were $15 million.
|Owner||Toronto Transit Commission|
|Engineer||McCormick Rankin Corporation|
|Architect||A. J. Diamond, Donald Schmitt & Company|
|Concrete Supplier||Dufferin-Custom Concrete Group|