Abstract Manager

This paper concerns the design of the bridge carrying Lake Shore Boulevard East  across the mouth of the Don River in the City of Toronto.  The river’s outlet into Lake Ontario was recently reconstructed to increase flow capacity, thereby reducing annual upstream flooding.  That effort included widening the mouth the river, which necessitated replacing the existing bridges carrying Lake Shore Boulevard East – a major arterial road that connects downtown Toronto to the eastern neighbourhoods of the City – with a much longer bridge.  The existing site consists of an eastbound bridge and a westbound bridge, each comprised of two-span, 50m-long, slab-on-steel girder superstructures on conventional concrete abutments and piers.  A new, four-span, 98m-long, 37m-wide, prestressed concrete bridge with semi-integral abutments was designed to replace the existing bridges.  Collaboration with the short-term owner – Waterfront Toronto – and the eventual owner – the City of Toronto – was paramount to the project’s success.  The design was driven by significant geometric challenges in the built environment.  The bridge was designed on the same alignment as three previous Lake Shore bridges, several dock wall structures, and the second-level Gardiner Expressway, all of which included deep foundations that the new design had to avoid or address.  The east end of the bridge terminates within the intersection of LSBE and the Don Roadway.  High flood elevations and the need to minimize the grade raise necessitated a more slender superstructure than could be achieved using concrete NU-girders. The existing abutments and centre pier were partially reconstructed and widened for re-use in the new bridge to reduce dewatering and demolition costs, including reinforcing the existing west abutment to become the centre pier in the new structure and the point of longitudinal fixity for inertial loads.  Complicated staging was necessary to maintain vehicular traffic, to enable construction of the many utilities that cross the bridge, and to facilitate dredging of two new spans of the bridge. Many design adjustments were necessary during construction to address found conditions on the site.  The bridge recently opened to traffic after four years of staged construction.