HIGH WINDS have torn a hole in the fabric roof of Canada's main stadium for the 2010 Winter Olympics, causing the air supported structure to deflate.
BC Place stadium in Vancouver is due to host the opening and closing ceremonies for the 2010 Games. Constructed in 1983, the roof is reaching the end of its 25 year design life.
It was designed by structural engineer David Geiger and has his signature low-profile cablerestrained air-supported roof.
The 190m by 231m superelipse structure has a 4ha surface but requires just 0.24kPa of air pressure to rise 27m above a reinforced concrete compression ring.
Last month a section of the 60,000 seat stadium's Teoncoated fibreglass roof tore away from the compression ring, forcing engineers to deate the structure.
'Because of the tear, we activated a controlled deflation of the stadium roof, ' said BC Place general manager Howard Crosley.
Deflating the roof caused three more tears in the fabric.
Crosley would not conrm the cause of the initial tear but ruled out snow loading, adding that the stadium's roof was draining normally without large accumulations of snow at the time.
Millennium Dome designer Ian Liddell said that the failure was likely to have been caused by a combination of factors, including snow and high winds.
'Snow load acts against the inflation pressure, reducing the tension in the fabric and making it more unstable in winds.' Winds reaching 115km/h tore through British Columbia on Friday and Liddell added that a very strong gust could have caused the initial tear.
'The building is surrounded by high buildings that were not there originally and these bring high winds down to ground level with strong turbulence, ' he said.
'Normally if there are high winds you can increase the air pressure in the roof to combat that, but a strong gust passing through the high buildings could have hit the roof with the force of a tornado. It would have been too quick for the guys in the stadium to do anything about it.' Crosley said that two panels of the roof would need to be replaced, with smaller tears repaired without replacing further panels.