When Gosnell Council in Western Australia commissioned a new pedestrian bridge to span the Canning River, the solution was a unique, architecturally designed lightweight structure made from advanced FRP composite materials.
Located in the Centennial Pioneer Park in Perth, the bridge is used by hundreds of pedestrians and cyclists a day as a link between residential areas and Albany Highway.
When the substructure of an old park bridge linking residential areas and Albany Highway started to erode, Gosnell Council decided to replace it with a wider and lighter bridge specially designed for the fragile environment.
The project managers Capital House Australasia architecturally designed the new 21-metre span bridge and engineered the site works. Fremantle-based Swarbrick and Swarbrick, manufacturers of iconic composite infrastructure and public artworks as well as marine craft, were chosen as the builder. They contracted Composites Consulting Group (CCG), an independent DIAB Group company, to engineer the bridge construction. Employees from the two companies worked side-by-side to create a lightweight, yet strong composite structure in Swarbrick’s Henderson-based facility.
The light weight of the completed 21 metre single span bridge meant it could be transported and installed in one piece, with four bolts on small footings causing minimal disturbance to the fragile environment and reducing costs.
“The access to install the bridge was very limited with only a narrow path leading to an open grassed area. We were able to project one end across the river and pick it up with the other crane on the opposite bank,” says Glenn Swarbrick.
The bridge structure is a hollow, U-shaped box made of e-glass skins over structural cores infused with fire retardant vinyl ester resin. Carbon capping tapes running the length of the bridge add the strength and stiffness required for the long bridge span.
All engineering was performed under the relevant Australian codes and standards as well as the Eurocomp Design Code. Along with the usual load cases for bridges, which include pedestrian walking and balustrade loads, the Gosnells pedestrian bridge is also engineered to resist various flooding-related load cases – an essential design consideration in a flood-prone region.
The bridge’s pier-free span also ensures that there is no impact on natural river flows and the riverbed.
Together with an improved concrete footpath network and lighting, the bridge will further encourage public access to the reserve and provide a safer river crossing in this popular parkland.