Infrastructure
Civil
Bennett Brook Bridge, Western Australia
The Bennett Brook Bridge was constructed as part of a 5km section of Reid Highway. The bridge is at a 45 degree skew with the brook. The initial design allowed for a surcharge at the brook area to reduce settlement time, followed by the construction of a 25m single span bridge structure. However, the surcharge was rejected by the local Aboriginal community because of the area's cultural significance.
FEATURES:
The sacred site status of the location meant the ground within a 40m wide strip straddling the brook could not be disturbed by construction plant or equipment. Only pedestrian entry was allowed to cross the 40m wide strip during construction. The solution proposed, and accepted by the local community, was for piled abutment foundations outside the 40m strip and a composite steel superstructure spanning 58m. The bridge deck is 20m wide and comprises six fabricated steel plate girders with a shallow, inverted arch-shaped profile.
Steel plate girders, 60m long, were fabricated, assembled into pairs for stability purposes and then transported to site on a steerable jinker. A 350t dual crawler crane was used to install the pair of beams, weighing close to 100t. Transfloor panels were used as soffit for the deck. This was a 75mm thick and 2,400mm wide, precast concrete panel, with length to suit the bridge deck width. The well-planned lifting operation of the pairs of steel plate girders, from behind the abutment, resulted in fast and trouble-free erection, despite the difficult access constraints imposed by the site. A 155mm insitu topping was then constructed to complete the deck slab.
BENEFITS:
The project was completed within the agreed schedule, despite the bridge being redesigned because of cultural heritage and geotechnical difficulties that occurred when construction was due to commence. Consulting Engineers Bruechle Gilchrist & Evans, the designers of the bridge, said: "This was a project which was both technically demanding, and which required a sensitive handling of the environmental and social issues. It is a credit to the team that the task was completed smoothly, on time, and with excellent collaboration with the Aboriginal community."
CLIENT: Highway Construction (on behalf of Main Roads WA)
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