Brisbane’s new bridge is a mess of masts and cables

June Cummings reports

The world’s first tensegrity bridge, it is a network of steel masts seemingly held in suspension by a delicate cross stitching of high wire tensioned cables. Linking the legal enclave on the city side with the South Bank arts precinct, it adds a ‘mad’ sculptural element to what is becoming arguably Australia’s most exciting city.
A Queensland government initiative, the Kurilpa Bridge did not come cheaply. It has a price tag of $64m. Design and construction was managed by the Department of Public Works in collaboration with the managing contractor Baulderstone Hornibrook, designers ARUP and architect Cox Raynor.
More than the sum of its parts, it means locals and tourists can promenade or pedal across the river to the city’s public art galleries, museum, library, performing arts theatres and concert halls. Then bathe in a string of artificial beaches on the riverfront, amid cafes and gardens before crossing a southern pedestrian bridge back to the city gardens and cultural precinct.
Looming bridge
Its ‘tensegrity’ design is a first to be applied to city bridge construction and it looms over the city’s north/south Riverside Expressway which carries 150,000 vehicles a day and the busy North Quay roadway.
Tensegrity, a design concept by American architect Richard Buckminster Fuller, is a balance between tension and compression where no two compression members (spas or steel masts) touch the same tensioned cable, allowing the structural shape to yield increasingly without breaking. It is a form that has been used internationally in sculpture and experimental architecture.
Described by Brisbane architect Cox Rayner, members and cables vary continually in angle, length and dimension so that no two parts of the bridge are alike, yet form a cohesive structure. In construction terms the bridge is a cable stay bridge, with a balanced cantilever form erected in prefabricated steel and precast concrete segments from piers founded on piles.
Limited clearance
In dimension the bridge is 470m long with a main span of 120m, deck thickness of 25cm and a clear width of 6.5m. The navigation channel beneath the bridge is 100m wide with a mid point clearance of 11.4m. It is built from 1500cu m of concrete, 400t of steel and more than 6.8km of cabling.
Angled upstream, the bridge is founded on two piers in the river and two piers on the northbank. It has a basic composite structure of steel deck, precast concrete slabs, steel structural masts and spiral strand cables ranging anywhere between 30mm diameter and 80mm diameter. Further stainless steel cables 16mm and 20mm in diameter applying the same tension principles as the primary structure hold up a central panelled canopy, which visually appears to float in mid air, running the length of the bridge.
To protect motorway and marine traffic beneath, the bridge is encased in impermeable glass screens.