‘Weak beam caused mall collapse’Comment on this story
Durban - A beam that had insufficient steel reinforcing bars and an unbonded concrete joint probably led to the Tongaat Mall collapsing, an expert engineer testified on Monday.
Dr Piet Pretorius told the department of labour's inquiry into the collapse that he did not believe that two columns, identified as columns 243 and 319, were responsible for a portion of the mall collapsing.
Two people were killed and 29 others were injured in the collapse in November last year.
Pretorius said the beam, identified as “beam seven”, had only six steel bars, and the concrete making up the beam was not poured in one session. One portion of the beam had been allowed to dry for two weeks before the rest of the beam was poured, creating a “cold joint”.
He said that there had been no bonding of the cold joint. He described it as a “bond failure”.
Pretorius, who was asked by design engineer Andre Ballack's firm Axiom Consulting Engineers to have a look at Ballack's design of the mall, said: “With only six bars it fails immediately.”
He said that had the beam not failed, column 319 would have failed.
He did not believe it had failed as it was still supported by scaffolding.
Beam seven, he said, failed when the form scaffolding - the scaffolding holding up the beam and concrete slab - was removed.
He said that as the scaffolding was removed the beam was required to support a weight of 150 tons - a weight it could not carry because of the weaknesses of the beam.
The steel that had been used had not failed, but it had been insufficient to handle the stresses caused by the 150 tons. He said this was evidenced by the fact that the steel did not break, but “the steel was pulled straight out of the concrete”.
Pretorius said Ballack's firm Axiom had been involved in the construction of numerous shopping malls.
He said that consulting engineers often have to deal with clients who change plans.
“The wish of the client is to do business. Changes (to plans) are the origins of problems,” he said, adding that often design changes were made as construction proceeded.
The inquiry continues on Tuesday.