TEXTILES.ORG
A fabric-clad pedestrian bridge is poised to become a landmark entry point to Western Australia’s in-the-works sports stadium.
Australian football fans ready to cheer on the 2018 Australian Football League season will travel from all across the country to attend the highly anticipated opening of the new Perth Stadium and Sports Precinct located on Western Australia’s Burswood Peninsula. They’ll arrive via an integrated transport system featuring two key elements: a modern stadium train station and a membrane-wrapped steel pedestrian bridge. Until then, a handful of companies and contractors are hard at work to ensure that the Government of Western Australia’s (WA) vision of the bustling, vibrant mecca it has been planning for more than five years comes to life on schedule.
Because of restricted parking on the peninsula, stadium visitors will be encouraged to cross over from East Perth, which is separated from the precinct by the Swan River. The new pedestrian bridge, scheduled for completion by mid-2017, will not only serve that purpose but will also stand as a new landmark and an entry statement to the stadium, with more than 14,000 people expected to use it on event days, according to the WA Government.
Symbolic structure
The bridge’s steel cable-stay design was submitted jointly by Australian engineering and construction company York Civil and Italian contractor Rizzani De Eccher, who ultimately won the contract in June 2015. When complete, the 400-by-9-meter bridge will feature a 65-meter-tall central structural arch to provide a focal point from distant viewpoints, according to York Civil.
Its structural support will be made visible in the form of two black and white arch ribbons, reflecting structural interdependency and the symbolic coming together of diverse cultures, built form and nature, the company explains. The design also represents the aquatic environment by taking the shape of living creatures, fluidity and movement. It has even been likened to the Wagyl—a snakelike creature believed by WA’s Noongar culture to have carved the area’s waterways.
Made of structural steel covered with membrane fabric, the bridge will comprise 1,500 tons of steel, 1.6 kilometers of concrete-filled steel piers and 1.5 kilometers of steel cables and strip lighting. To minimize impact on the waterbed, the work includes four piers: just two in the channel and two on the riverbanks. The supporting arches are made of tubular steel in a reticular structure, with a suspended mixed steel-concrete deck that also rests on the central piers and the trusses.
Silt curtains were installed before in-river construction to control suspended soil particles in the waterway, according to information on the Perth Stadium website. Two 130-meter causeways were built on both sides of the river to create platforms from which the piers were installed. The central span was assembled on the peninsula, while the other arches and decks were assembled on the causeways.
Cladding challenges
In summer 2016, Brisbane-based tensile membrane structure specialist MakMax Australia was awarded the contract to design, supply and install the fabric cladding system that will completely encapsulate the primary steel framework, says Kim McHugh, marketing manager. “Our concept and proposal has involved multiple design workshops and prototypes to develop an entirely new system of tensioning and installing the fabric,” she notes, adding that the company is also responsible for the design of all secondary items required to support the fabric cladding.
The bridge’s arches will be subdivided into multiple short panels. MakMax plans to fix the panels to the steel modules before the modules are launched into the river and lifted by a steel erector. “Because of the large wind loads that installed panels could generate during lifting, we are only allowed to fix the fabric to the steel in long rolls,” McHugh explains. “These will be planned in such a way that once the steel is lifted, the fabric rolls can be easily unfurled—like sails—and then tensioned against one another to form the completed tensile structure.”
The limited access for installation will be one of the company’s biggest challenges, as it must take place after all steelwork is raised and the primary structure is in place over the water. Access can only be from inside the steel structure to many areas, McHugh says, noting that “very few projects we work on completely enclose all supporting framing.”
Triangular support
MakMax’s fabric of choice is Chukoh FGT-800, manufactured by Chukoh Chemical Industries Ltd., as it meets the design specification for translucency as well as the engineering requirements for strength. “Chukoh FGT-800 has been used extensively for Taiyo projects worldwide and was a natural choice based on our experiences of fabricating and installing previous project with the material,” McHugh explains. Chukoh’s FGT series consists of glass fiber yarn cloths impregnated with fluoroplastic PTFE that are then sintered. The fabric offers heat resistance of up to 800 degrees Celsius, UV resistance and anti-adhesion and water-repellent properties. Approximately 15,000 square meters will be used for the bridge’s surface area as well as its deck, the underside of which is also clad.
The fabric will be supported at three points: The top piece will have a custom-designed extrusion to allow MakMax to clip the fabric rolls to the steelwork, and the lower two corners will be circular hollow sections fixed to the primary steel chords at regular spacings. These pipes will be rolled to match the overall shape of the bridge. “Outside of these three longitudinal lines, the fabric will be self-supporting and find its own natural form under the pre-tension loads applied at install,” McHugh says.
Final details
As with any outdoor structure, nature poses its own set of challenges. “Wind is always a consideration when installing fabrics, but over the water and at considerable height, this project has increased exposure to the elements,” McHugh says. “Other factors we must absorb include the ability to remove the hangar cables for the deck one by one, so our fabric must be detailed to allow a cable termination to pass safely through.” In addition, strip lights will be placed along the chords to illuminate the membrane surface of the white arches. The lights will have a wide-ranging color palette that can be programmed based on an event’s requirements. Because the fabric will be internally lit, careful planning is required to ensure all seams and details are positioned to give a strong architectural appearance, McHugh notes.
McHugh expects the bridge to take shape late in 2016, with construction expected to be complete in 2017. The development also includes a network of walking and cycle tracks, restaurants, playgrounds and picnic areas to encourage daily use of both the bridge and the peninsula’s attractions.
Holly Eamon is a Minneapolis-based writer and former assistant editor on the Review.