Roof of $10m stadium sagged during construction

Stadium Southland's collapsed roof. Photo / NZPA

The roof of Stadium Southland, which was lowered 15 metres and had its pitch reduced to appease neighbours, suffered sagging problems during construction.

Demolition crews are looking to clear the remains of the $10 million, 10-year-old stadium after what may have been the heaviest snowfall in 50 years caused its roof to collapse on Saturday morning. Questions are now being raised about its strength.

Representatives from both the Invercargill City Council and the Southland Indoor Leisure Centre Charitable Trust, which owns the stadium, met this afternoon to discuss the incident.

Trust chairman Acton Smith told the meeting that it had appointed local engineer Graham Cole to undertake a "thorough, independent structural engineering review" during the coming weeks to ascertain the cause of the roof collapse.

"It will be some time before we know the cause," said Invercargill Mayor Tim Shadbolt.

He said he had received support from several builders and engineers for comments he made to media, expressing concern about the initial construction of Southland Stadium.

He said rumours had been rife around the city for several years about the quality of the work.

Media reports from 12 years ago show plans for the stadium had to be revised to appease disgruntled neighbours, who were concerned about shading the height of the building would cause to their properties.

As a result, the roof was lowered 15m and the vertical shading angle reduced to below 20 degrees.

Then, during construction, there were problems with the roof when several of the huge steel trusses across the community courts - the area where it collapsed at the weekend - had sagged following installation.

At the time, trust chairman Ray Harper said the movement was slight - less than 10cm in the worst case - and was not unusual in such a large project. He said there were no safety concerns because the problem was not serious and it had been detected early.

"It will be perfect when the job is finished; it has to be to have certification, anyway."

But in a letter to Mr Shadbolt, structural engineering expert John Scarry, of Auckland, said a modern design should not need structural strengthening at all.

In 2002, Mr Scarry wrote an "open letter" in which he exposed "the parlous state of the structural engineering profession and the construction industry in New Zealand".

He told Mr Shadbolt several major stadia had been on the verge of collapse during or immediately after construction, under no snow loading at all.

"These include the Waitakere Trusts Stadium, which was overstressed 900 per cent at its main support points, and the Vector Arena which had, I believe, three major defects, two of which almost caused total collapse."

Mr Scarry claims one of the major defects related to eccentric steel cleat connections which, until recently and almost universally, had been under-designed in New Zealand, causing several to fail as a result.

He says improvements were made after the Heavy Engineering Research Association investigated Vector Arena, which was closed in 2005 during construction, for emergency repairs.

"The near total failure of the eccentric cleat joints was identified and strengthening designed and installed."

- NZPA

* An earlier version of this story wrongly described Calder Stewart Construction as engineer of Invercargill's Southland Stadium. NZPA apologises for the error and any distress caused. Calder Stewart Construction was involved in the construction of the neighbouring Southland Velodrome, which came through the snowstorm undamaged.