Construction defects, design flaws, and snow caused the collapse of a New Zealand sports stadium, a report has found.
Following heavy snowfall, the Southland Stadium at Invercargill collapsed on 18 September 2010.
An investigation commissioned by the Department of Building and Housing (DBH) and jointly conducted by independent experts Hyland and StructureSmith found that four key factors contributed to the collapse.
Along with heavy snowfall, these included problems associated with remedial works during construction, construction defects, and design problems. The report found that the volume of snow on the roof did not exceed the snow loading standard at the time and that the snowfall, while certainly not helping matters, would not in and of itself have been sufficient to cause the collapse.
Instead, the investigators discovered that remedial works, including steel fabrication and welding carried out during construction in response to observations of a sagging roof, were not sufficient to ensure the integrity of the stadium.
Southland Sports Stadium collapse such a deficiency, the Department says, demonstrated inadequate supervision of the remedial construction work. “If the stadium had been constructed in accordance with the design documents for remedial works and construction standards of the time, it is unlikely it would have collapsed under the snow, sleet, and rain on 18 September 2010,” the Department says in a statement.
DBH Chief Executive Katrina Bach says the department has accepted a recommendation in the report that it provides guidance on the design of roof structures that are subject to snow loading. Bach says the Department is looking into a recommendation that building owners install snow alarms on steel structures over 20 meters long to warn occupants in case of excessive snow loading, adding that the Department would issue a Practice Advisory to Territorial Authorities to encourage building owners to regularly inspect such ‘long span’ steel structures for possible defects. “As a matter of course, responsible building owners regularly inspect and maintain their building stock and the Practice Advisory will provide additional guidance on what they should be looking for in those inspections,” Bach says.
DBH’s Deputy Chief Executive of Building Quality, David Kelly, says the department which has referred the investigation report to the NZ Police and the Department of Labour, is already implementing changes to design, construction, and quality assurance processes as part of its response to the Canterbury earthquakes. Improvements, he says, will come through training, building code adjustments, risk-based consenting, and – when they are introduced – design and feature report.
“We’re working with the industry to highlight the importance of skills, competency, and training to ensure all commercial buildings are built right the first time,” Kelly says.
Mayor Tim Shadbolt had declared that there had been prior concerns about the stadium’s roof structure. The roof was told to be too flat. The Ministry of Business, Innovation, and Employment reported that the roof collapse is accounted for heavy snow and defects in the construction of the steel tube trusses in the roof. The report has found that the collapse has likely started in one of the roof’s beams which is a chain reaction passed through other trusses. The spine trusses then fell to the ground and the support columns collapsed. The same report also highlighted concerns about areas of the stadium that involved design and construction modifications and welding on site.
There were several investigations into the damage, construction defects, and material deficiencies that were identified as contributors to the collapse. The New Zealand Police Department involved in the investigation did not file any charges, no criminal liability was found. A new stadium renamed ILT Stadium Southland was opened in 2014.