“The widening of the 525-metre-long Breede River Bridge is considered an example of outstanding civil engineering design and construction which, despite environmental, traffic and construction constraints, was completed on time and within budget,” – Hennie Niehaus, Aurecon Technical Director.
The Breede River Bridge, originally constructed in 1951 with a total length of 525 m, is one of the longer river bridges in South Africa. The bridge was to be widened as part of a larger contract for the rehabilitation of the MR298 between Worcester and Wyzersdrift through Rawsonville. In 2010, the Western Cape Government’s Department of Transport and Public Works appointed Aurecon for project management, design of the bridge structure, procurement and construction supervision of the project.
The initial concept was to upgrade the MR298 to an 11.4 m wide road. Limited funds reduced the proposed widening to an 8.6 m road width across the bridge. As environmental approval for work in the river would have delayed implementation, the project team designed a solution that could be constructed without any work in the water. This also reduced the risks associated with flooding during construction.
The design option adopted due to these constraints was to widen the bridge on both sides using precast beams supported on cantilevering formed by cast-in-situ reinforced concrete corbels attached to the existing piers and externally stressed together using high-yield steel tie bars. The ingenuity of using hanging moving gantries to complete construction work from on top of the existing deck also limited the environmental impact.
The work included other technical and construction challenges necessitating the development and implementation of solutions. These included maintaining traffic flows during construction, maintaining flow for a sewer and a water main attached to the bridge, maintaining and relocating optic fibre telecommunication lines over the bridge, dealing with inconsistencies in the dimensions of the old bridge, and developing repair solutions for parts of the old construction, such as jacking up one of the decks to install bearings.
Extensive bridge repair work was also successfully completed, including pier protection collars, partial reconstruction of abutments, large spall repairs and the jacking of the north abutment to install new bearing pads. The widened bridge provides a much safer crossing for all users. Several social aspects were considered during the project, including continual interaction with the community during construction to mitigate the effects of the construction works.
“The project was completed in November 2017 to high standards and to the client’s requirements. The finished bridge provides an aesthetically pleasing and safer crossing for both vehicles and pedestrians over the Breede River. The cooperation from the main contractors and subcontractors, as well as the working relationship that developed between the contractor’s personnel and the supervising staff, was exemplary,” says Niehaus.