Winter Sports
Image 1: Up close and personal - measuring light and turfgrass quality in the ETFE test rig at the commencement of the winter trial (April 2008)
from a turf perspective.
Three conclusions were particularly important:
- The pitch design should focus on growing turfgrass in the stadium as opposed to relying on any turf replacement for areas that might get worn out (it was also at this point that the Desso GrassMaster turf reinforcing system was first recommended)
- The pitch should be designed with a perimeter of artificial turf to eliminate the significantly worse turfgrass growing conditions that would be found around the edge of the pitch
- The pitch construction budget (which had been set well in advance of any turf work commencing) was realistic
Developed design - Preliminary design was completed in May 2008 and moved straight into developed design. This stage required much more coordination with the wider design team to select the most appropriate pitch design option commensurate with the available budget. This was clearly no ordinary ‘off-the-shelf’ pitch - its design did not need to follow those used for conventional outdoor stadium pitches - and some fairly important design questions had to be asked, including:
- What type of rootzone, irrigation, and drainage systems would be best suited to the permanently-roofed stadium design?
- How would the environmental conditions within the stadium bowl be monitored and linked to pitch maintenance?
- Would the proposed design stand up to
Image 2: Computer modeling of predicted light levels was undertaken by Aurecon using Ecotect software. Computational fluid dynamics modeling (CFD) was also used to model wind movement and CO2 levels
international peer review?
By the end of the developed design stage in October 2008, design components for building the pitch including subgrade and surface shape, subgrade drainage design, rootzone selection and profile design, irrigation system design, turfgrass species selection and establishment were complete. Serious consideration was also given to establishing the surface using turf harvested from Carisbrook as a contingency in the event of construction delays, but a decision was made in late 2009 to establish the surface on site from seed.
There were two other important components of the developed design stage. The first was international peer review, both at a scientific level and at a practical turf management level. This review included using the Sports Turf Research Institute in Bingley to benchmark the predicted light levels for the stadium against northern hemisphere stadia known to suffer from turfgrass decline during the winter period. The second important component of the developed design stage was a visit to the Etihad Stadium in Melbourne to gain a better appreciation of turf management challenges in a stadium with a retractable roof, which was then followed by a visit to the Eden Project in Cornwall, one of the most successful facilities growing plants under an ETFE structure.
Detailed design - The final section of the pitch design stage involved the preparation of specifications and schedules for tender, which were completed in February 2010. By this stage the stadium was about eight months into
the building contract. The essential design components of the pitch were:
- a 300mm deep sand profile placed over a drained subgrade, with the top part of the profile being made up of a sand/soil/compost rootzone specially blended off-site
- a strategically located zeolite-amended sand rootzone layer
- sub-surface irrigation as well as a conventional pop-up irrigation system
- buried soil moisture sensors for optimum soil moisture management
- Desso GrassMaster turf reinforcement - the first stadium in Australasia to use such a system
- a 3m wide perimeter boundary of artificial turf that was to marry seamlessly with the natural turf (total pitch dimensions are 132m by 81m)
Construction facts and figures
The space age EFTE roof was originally developed by German chemical company Hoescht in the 1970s as a film for solar collectors, because of its unique properties and resistance to UV radiation and atmospheric pollution. The oldest ETFE structure in the world is the Mangrove Hall at Burger’s Zoo in Arnhem, Netherlands, which was completed in 1982.
ETFE roof structures are made up of inflated ‘cushions’. The material is extruded into thin films and supported in an aluminium frame, which itself is supported on the building frame. A typical ETFE cushion weighs 2-3.5 kg/m2 and the cushions are inflated to about 220 Pa to give them structural stability. The
Image 3: Assembly of the final arch truss in November 2010 58 PC OCTOBER/NOVEMBER 2011
Image 4: Commencement of subgrade preparation in October 2010
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