City to review technical assessment after stadium roof bolts show ‘distress’

THE STRUCTURAL integrity of the Cape Town stadium’s roof is not under any threat of failure or collapse, says the city, despite routine inspections having revealed “certain bolts showed signs of distress”.

The discovery has prompted the city to commission two technical assessments and a forensic inquiry so far this year.

The technical assessment, carried out by the original professional team who built the roof, a joint venture by US tensile structure experts Birdair and German rope and cabling engineers Pfeifer, revealed small bolts had been subjected to “excessive stresses” over time.

Acting mayoral committee member for finance Johan van der Merwe said yesterday despite the problems, the structure was not at risk of “failing”.

The structure’s complex design and construction made it difficult to determine the exact cause and extent of the defects, and it was necessary to carry out further assessments, he said.

“It must be noted that the failure of any of these bolts would not cause any structural element or fixture in the roof to collapse. Nevertheless, they form part of the roof structure and need to function in an optimal manner.”

The original contractors have since carried out the repair and replacement work as part of its duties and liabilities under the original contract.

Still, the city has appointed an independent firm of engineers and technical specialists Arup (Pty) Ltd – a global company with

a Cape Town office – to review the technical assessment, conduct an independent forensic investigation and provide expert guidance on issues of liability.

In July, the city manager issued a public notice that the contract’s original expiry date of June 30 had been extended for a year.

The reasons for this, given by the city’s supply management in a report to the mayoral committee on October 4, were due to the scope of work and the confirmation of the contract sum, estimated at R627 000.

At the time of its construction in 2009, the stadium’s over 30 000m2 tensile roof was the largest of its kind in the world.

Made of translucent PVC and glass and a combination of steel and radial cables, it’s designed to allow for maximum light and to dampen noise.

Rainwater and storm water is also harvested on the roof as part of green building practices.

Yesterday the city said: “Although the city has confidence in the professional team and contractor, it was felt prudent, due to the structural complex nature of the roof, to appoint independent experts, who were not involved in the original design and construction, to conduct a further technical assessment.

“It was deemed sensible to ensure that all aspects had been covered as identified by the first assessment and that this be done while the roof is still under guarantee,” said Van der Merwe.

The city could not immediately say when the guarantee expires.

According to the supply chain management report, the independent forensic inquiry was required to “provide expert guidance around the question of liability in relation to other defects”.

“With the reason(s) for the defects and the extent of the defects, or the potential extent and risk of re-occurrence, not obvious, it is very difficult to pre-empt which party would be liable for the cost of repairs, especially in the possible event of any recurrence,” said Van der Merwe.

Arup specialises in the failures of engineering structures, contractual claims and dispute resolution. It has also been involved in the design of many stadiums and airports around the world.

Its assessment review is due to be completed within the next three months.