Sydney's Stadium Australia is undergoing a massive reconfiguration to allow it to be used to the maximum. Steve Turner reports.
In sports mad Sydney, rugby league, Aussie rules football, soccer and rugby union dominate the sporting scene with local clubs figuring prominently in national competitions.
Built for the Sydney Olympics, Stadium Australia was the focal point for the 2000 games, but once finished construction mnanager Multiplex Construction began a major programme of works to convert it from an athletics stadium to one fit for multi-purpose sporting events.
Constructed at a cost of $530M, with a seating capacity of some 115,000, the changes will bring spectators closer to the action.
Despite an ongoing programme of works, the stadium has become Australia's formost sporting venue. As John Kleindienst, senior manager asset service and technical director for Stadium Australia explains. 'At no time were there fewer than 33,000 seats available. Basically people were watching sport in a building site.'
The changes have seen the removal of the athletics running track, which has been relocated to the Sydney Athletics Centre next door.
To accommodate the different sports, lower sections of two side stands are moved in and out by 15.6m, to configure the shape of a rectangular rugby/soccer pitch when in a forward position, and a larger oval shaped Aussie rules pitch when moved back.
The creation of a larger 170m by 128m playing area also allows the stadium to be used for cricket. Seating capacity is now 80,000 for rugby and soccer and more than 73,000 for sports requiring the bigger pitch 'The original intention for the two side stands was for the two lower tiers to be moved forward permanently in a one off move to create a rectangular pitch, ' Kleindienst explains. But the injection of an additional US$2.7M the owners and designers came up with a plan for two moving stands that would ensure its maximum usability.'
But creating the two 3,000t stands was no easy task, especially when the designer and supplier of most of the componentry withdrew from the project just five months prior to the proposed completion date.
A team was assembled by Multiplex, free from any contractual constraints, to develop a system in the time available, bringing on board Sinclair Knight Merz and engaging Structural Systems to procure the parts.
Each tier is 100m by 30m, of post-tensioned cast insitu concrete on steel and concrete columns, with the concrete column bases designed specifically to allow sliding assemblies to be installed. Both were extensively strengthened following the Olympics.
Insitu prestressing was specified to ensure that the inclined deck, which acts as a stiff diaphragm does not crack during repeated movements.
Each tier moves on 14 support raker beams each with three bogies. On the lower level the bogies run on a single common rail with two wheels per bogie.
The upper level bogie is two wheeled, running on a common axle on twin rails.
One of the most innovative aspects was marrying the bogies to the columns which was done using Epirez 'chocolate orange' epoxy, a substance normally used for setting marine engines in super tankers.
'The bogies on each stand are powered by 14, 1.1kW electric motors, ' Kleindienst explains 'with all the assemblies locked in place with earthquake restraints. The system is controlled using an intricate computer system that ensures all the bogies are moving at exactly the same rate and remain parallel.'
When in the forward position, the 15.575m gap behind the stand must be bridged. At lower level a steel framed gallery is suspended from the stand with a trailing ramp, at the entry point which runs over the concourse slab. At the upper level a bridge, stored flat under the stand in the closed position, comes into play.
When the stand is retracted the rails encroach on to the larger pitch, so to avoid injury to players they are set in trenches below the pitch surface. These are then covered by sod pans, shallow boxes filled with soil and grass sitting between locating angles fixed to the concrete trenches. Currently pans are placed on a trolley to be moved manually, but an automated system is planned to speed up the operation.
At the same time, the north and south ends, in effect constructed as temporary stands for the Olympics, have been completely renovated. The post Olympic plan was to complete the circular external form of the building, moving the lower sections 15m closer to the field, and cover with a roof spanning the main arches.
As soon as the games were finished the corner sections of the stands were removed, and the ground beam extensions constructed. The upper bowl was then demolished.
Consultant Sinclair Knight Merz, who has been the stadium's structural, civil and building services engineering designer from day one, came up with a system using technology derived from incremental bridge launching and slid the lower bowl forward.
The column bases were originally built with a removable stub. Once the ground beams were completed, the stubs were removed and a sliding shoe with a stainless steel sole installed.
The whole structural segment was then securely braced and jacked forward over rubber backed Teflon pads laid along the newly cast ground beams.
The work has lead to a reduction in the number of seats in the two ends from 53,000 to 43,000.
Later this year work will begin constructing a roof for each of the two ends, which will connect in to the existing side stand roofs extending protection from the weather to 90% of the seats. It will also ensure that any crowd noise generated will be better contained creating an electric atmosphere at top events.
Stadium Australia should provide the sports mad Australians with a state of the art sporting venue for many years to come.