THE OFFICIAL inquiry into last year's Injaka bridge collapse in South Africa has heard of errors in the deck-launching procedures and that cracks in the deck were ignored.
Fourteen people died when the incrementally-launched second span of the seven span concrete box girder crossing collapsed last July. Shear failure of the lower flange over temporary bearings at the second pier has been blamed (NCE 21 January). Under questioning last week workers from main contractor Concor Construction admitted that Teflon pads were sometimes fed into the bearings the wrong way round because it was easier.
These 600mm by 350mm pads were meant to move with the deck over the 1m by 1m bearings and allow it to slide smoothly. The pads should have been inserted with the long side at right angles to the deck. However, workers said that on occasions the pads were rotated by 90degrees and fed in lengthways, halving the area of contact with the support and doubling the pressure on the underside of the deck.
The inquiry was also told this week that cracks in segment two of the deck, which was resting over an intermediate support at the time of the collapse, were ignored by designer VKE.
Concor contract manager Lesley Wardaugh said he had pointed out to VKE a series of 0.5mm wide cracks in the segment's internal diaphragm wall.
The inquiry heard that assistant resident engineer Marelize Gouws, who died in the collapse, told bridge designer Johan Bischoff about the cracks but was instructed over the telephone to carry on with the launch. She was then told to release four of the segment's 18 prestressing cables the next day to close up the cracks.
This week the South African Department of Labour's investigating expert Andries Oosthuizen will take to the stand. He is expected to agree with experts appointed by VKE and Concor that the trigger for the collapse was the failure of the deck's flange over the intermediate support. But sources claimed he was also likely to point out 'more fundamental errors'.
The inquiry, held at Council of Scientific & Industrial Research offices in Pretoria, is expected to continue until 19 February.