The Mount Henry Bridge is a pair of parallel bridges which carry the

Kwinana Freeway The Kwinana Freeway is a freeway in and beyond the southern suburbs of Perth, Western Australia, linking central Perth with Mandurah to the south. It is the central section of State Route 2, which continues north as Mitchell Freeway to A ...

and

Mandurah line The Mandurah line, also known as the Southern Suburbs Railway, is a suburban railway line and service in Western Australia, linking Perth's central business district (CBD) with Mandurah to the south. Operated by the Public Transport Authority ( ...

across the

Canning River The Canning River ( or ) is a major tributary of the Swan River in the South West Land Division of Western Australia. It is home to much wildlife including dolphins, pelicans, swans and many other bird species. Source and route With headwate ...

Perth Perth () is the list of Australian capital cities, capital city of Western Australia. It is the list of cities in Australia by population, fourth-most-populous city in Australia, with a population of over 2.3 million within Greater Perth . The ...

, Western Australia. At long, the Mount Henry Bridge is the longest bridge in

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

. The first bridge opened in 1982 and carries the southbound freeway carriageway and both tracks for the Mandurah line. The second bridge opened in 2006 and carries the northbound freeway carriageway. The first Mount Henry Bridge was built as part of an extension of the Kwinana Freeway from

Canning Highway Canning Highway is an arterial road in Perth, Western Australia, linking the inner Perth suburb of Victoria Park, Western Australia, Victoria Park in the north-east, to the port city of Fremantle in the south-west. The road is mostly a four-l ...

to South Street. Construction started in June 1979 and it opened to traffic on 9 May 1982. It was built by Clough and Sons for $13.5million. The second Mount Henry Bridge was built as part of the construction of the Mandurah line. It was originally planned for extra lanes to be added to both sides of the bridge and for the railway to go in the middle of the bridge, but this was changed so that a new bridge would be built on the western side of the existing bridge, and that the Mandurah line would go on the original bridge. Construction began in May 2004 and the new bridge opened to traffic on 22–23 January 2006. The Mandurah line opened on 23 December 2007. The new bridge was constructed by Leighton Contractors for $23million.

History

First bridge

The 1955 ''

Plan for the Metropolitan Region, Perth and Fremantle The 1955 ''Plan for the Metropolitan Region, Perth and Fremantle'' (also known as the ''Stephenson,'' or ''Stephenson-Hepburn Report'') was prepared for the Government of Western Australia by Gordon Stephenson and Alistair Hepburn. The plan ...

'' said that the future Kwinana Freeway would cross the Canning River near the Mount Henry Peninsula, but when the

Metropolitan Region Scheme The Metropolitan Region Scheme (MRS) provides the legal basis for land use planning within the Perth metropolitan region. It classifies land into broad zones and reservations and is administered by the Western Australian Planning Commission (WAP ...

was gazetted in 1963, it had the freeway crossing the Canning River slightly downstream, at Deep Water Point. In 1967, the proposed bridge location was changed back to the Mount Henry Peninsula, after objections by the

City of Melville The City of Melville is a Local government areas of Western Australia, local government area in the southern List of Perth suburbs, suburbs of the Western Australian capital city of Perth, east of the port city of Fremantle and about south of ...

. This was despite concerns about the freeway spoiling the untouched shoreline of the peninsula. The

Parliament of Western Australia The Parliament of Western Australia is the bicameralism, bicameral legislature of the Australian states and territories of Australia, state of Western Australia, which constitutes the legislative branch of the state's political system. The parl ...

approved this in 1975, and so the Metropolitan Region Scheme was amended to include the Mount Henry Peninsula route. The first Mount Henry Bridge was built as part of a extension of the Kwinana Freeway from

to South Street. It was designed by engineers from the Main Roads Department. Thirteen preliminary designs were created, of which nine were developed further. The eventual design, a nine-span

prestressed concrete Prestressed concrete is a form of concrete used in construction. It is substantially prestressed (Compression (physics), compressed) during production, in a manner that strengthens it against tensile forces which will exist when in service. Post-t ...

bridge, was chosen due to its limited visual impact on the landscape and because it best allowed for boats and water skiers to use the river. The contract to build the bridge was awarded to Clough and Sons. Construction began in June 1979. The bridge was constructed using a temporary cable-stayed truss and

formwork Formwork is Molding (process), molds into which concrete or similar materials are either precast concrete, precast or cast-in-place concrete, cast-in-place. In the context of concrete construction, the falsework supports the shuttering mold ...

which was moved along the bridge as it was built, making it unnecessary to use temporary piles in the river. The 242 concrete deck segments and sixteen diaphragm segments were fabricated onsite. The bridge and freeway extension were opened on 9 May 1982 by the

premier of Western Australia The premier of Western Australia is the head of government of the state of Western Australia. The role of premier at a state level is similar to the role of the prime minister of Australia at a federal level. The premier leads the executive br ...

, Ray O'Connor. The bridge cost $13.5million to build.

Second bridge

The second bridge was built as part of Package E of the construction of the

. This package was managed by Main Roads Western Australia and consisted of modifications to the Kwinana Freeway to make way for the Mandurah line. The original bridge was strengthened to withstand the weight of trains. The contract for Package E was signed with Leighton Contractors in January 2004. Construction began in May 2004. The existing Mount Henry Bridge was originally planned to be widened, but Leighton proposed building a second bridge on the western side instead, which reduced traffic disruptions and saved $17million. The bridge was Incrementally launched. As the spans were considered too long for incremental launching, temporary piers were constructed between the permanent piers. The new bridge opened on 22–23 January 2006, allowing work on the rail corridor to begin on the original bridge. The whole bridge widening project cost $23million. The Mandurah line opened on 23 December 2007.

Design

The original bridge is long, wide, and built from post-tensioned concrete. It is a twin-cell concrete

box girder A box girder or tubular girder (or box beam) is a girder that forms an enclosed tube with multiple walls, as opposed to an i-beam, - or H-beam. Originally constructed of wrought iron joined by riveting, they are now made of rolled steel, rolled ...

bridge which was constructed segmentally. It carried three freeway lanes in each direction and had a shared path cantilevered underneath on both sides. The second bridge was designed to fit in with the first bridge. The piers were designed to complement the original piers, but due to the new bridge's smaller size, the piers were not designed to be identical. As there were space constrains, the second bridge overlaps the original bridge but does not touch it, resulting in them appearing as a single continuous structure. In 2024, the Mount Henry Bridge was awarded an Engineering Heritage Marker by

Engineers Australia Engineers Australia (EA), known formally as the Institution of Engineers, Australia, is an Australian professional body and Non-profit organization, not-for-profit organisation whose purpose is to advance the science and practice of engineerin ...

. The bridge has also been on the

City of South Perth The City of South Perth is a local government area in the inner southern suburbs of the Western Australian capital city of Perth about south of Perth's central business district. The City covers an area of , maintains of roads and a littl ...

's local heritage register since 2000.

References

External links

Mt Henry Bridge – 2012 Booklet
on Engineering Heritage Australia
Mt Henry Bridge Widening – 2012 Booklet
on Engineering Heritage Australia
Design & Construction of Mt Henry Bridge
on Engineering Heritage Australia
Engineering Heritage Marker interpretation panel
on Engineering Heritage Australia {{Australian railway bridges Landmarks in Perth, Western Australia Road bridges in Perth, Western Australia Railway bridges in Perth, Western Australia Bridges completed in 1982 Bridges completed in 2006 1982 establishments in Australia Recipients of Engineers Australia engineering heritage markers