Stirling Bridge / Landscaping

Values

the place demonstrates the growing use of concrete as a structural material in mid twentieth century.

the place is associated with the development of major metropolitan infrastructure in the mid twentieth century.

the place demonstrates the characteristics of a substantial concrete bridge, designed to carry a high volume of traffic over a major crossing.

the place is a significant landscape element of Fremantle and the Swan River, with the design engineered to create a clean, simple shape.

the place demonstrates a high degree of technical achievement, recognised at a national level.

Physical Description

Stirling Bridge and Landscaping is a double lane prestressed concrete road bridge spanning the Swan River between Fremantle and North Fremantle. The bridge is seven spans, approximately 418 m long, 18 m wide and sits approximately 9 m above the Swan River at its highest point.

This bridge is oriented approximately northwest-southeast and consists of seven spans, set at varying lengths to compensate for the difference in height between north and south banks, and for aesthetic impact. The bridge abutments consist of concrete foundations, set back from the river edge on both sides to allow riverside traffic. The southern abutment is substantial, backing onto eight-meter-high limestone cliffs.

The bridge deck consists of four lanes with a 2 m wide footpath along the southwest (downstream) face. The bridge body consists of post-tensioned segmental spine concrete segments (also known as a “box girder” arrangement), set in pairs and sitting on top of the pylons via steel roller bearings to absorb movement. The bridge pylons are similarly composed of reinforced concrete, the foundations consisting of .73 m steel shell tubes driven to depths of 50 m and then filled with concrete. A water main, as well as power and communication ducts, are set through the inside of the precast concrete segments and under the footpath slabs.

The surface of the bridge consists of a bitumen road and concrete kerb. A galvanised steel safety barrier separates the road from the pedestrian path, which is surfaced with concrete slabs. The safety barriers on the outermost sides consist of galvanised steel tubes and railing.

History

Noongar people living around the Swan Valley in the pre- and early contact period can broadly be described as comprising small family groups moving through the landscape in response to seasonal change, utilising a toolkit of wooden and flaked stone tools and grinding stones, notably of quartz, dolerite and chert. The artistic culture of the Noongar people was expressed in painted and engraved art in a wide variety of forms, relating to a complex spiritual worldview that incorporated a connection to the natural world, and the remembrance or ongoing influence of ancestral and spiritual figures.

The Noongar groups living in and around the greater Perth area were collectively known as the Whadjuk, while the families living in the area of Fremantle known as the Beeliar.

This way of life was interrupted in 1829 with the establishment of a British settlement at the Swan River. British settlement expanded rapidly in the Fremantle area, mostly on the south side of the Swan but with a road along the northern side linking Perth and Fremantle in 1851.

As part of a government initiative to improve port facilities around the state, Fremantle Harbour underwent major expansions in the 1960s to improve its container shipping capacity, and Main Roads Western Australia was also substantially developing major transport routes in the metropolitan area. As a result, a new road bridge was proposed at Fremantle to reduce the load on the existing infrastructure.

One of the technological advancements that enabled this ambitious infrastructure development was the use of prestressed and reinforced concrete, which in the 1960s was beginning to dramatically change Perth’s built environment.

Two major concrete bridges had been built over the Swan River in the in the metropolitan area by this point. The first was P3631 Causeway Bridges (RHP), completed in 1952 and was designed and built by the Department of Public Works and the Main Roads Department. The second, P4795 Narrows Bridge (RHP), was designed by engineering firm Maunsell, Posford and Pavry, and constructed by Christiani & Neilson A/S of Copenhagen as well as J O Clough & Son of Perth. Given the success of the Narrows Bridge, Maunsell was then engaged to design a new road bridge over the Swan River at Fremantle in the 1960s, which included architectural advice from Perth architects Cameron, Chisholm and Nicol. The tender for construction of the bridge was awarded to J O Clough & Son in 1972, with construction beginning the same year.

While piles were being driven into the riverbed, 292 concrete box units were cast at Kewdale, then transported to Fremantle and stored on site. The pylons were formed through specially built formwork, with the concrete poured via a crane barge. The concrete bridge units were assembled via a steel truss frame that stretched the length of the river, which included a rail mounted trolley capable of shifting in multiple directions to fit successive blocks together. Construction also included the use of post-tensioning, using steel wire routed through ducts in the concrete to hold the units tighter, with this pressure increasing as more load was added from above. As a result of these design considerations, the new bridge was able to be built without additional cross-members (diaphragms) between the spans, giving the overall bridge a distinctive, clean design.

Stirling Bridge was completed 1974, and officially opened by Premier Charles Court, and at the time of its unveiling was the longest public road bridge in the state. The elegant aesthetics and innovative construction method saw the bridge win two awards, the Engineering Excellence Award from the Association of Consulting Engineers and the Award for Excellence in Concrete from the Concrete Institute of Australia.

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