LEGAL RESTRICTIONS on the disclosure of the final report into the disastrous 1996 collapse of the Koror-Babeldoab bridge in the western Pacific are threatening plans to catch up lost time on the Kingston Bridge strengthening project in Glasgow.
A senior Scottish Office spokesman confirmed this week that approval of revised strengthening plans for Kingston Bridge had been delayed as it had been unable to obtain the results of the investigation (NCE 5 May). Continuing legal action in the tiny Republic of Palau where the bridge collapsed means the results remain secret.
'We certainly can't approve any new proposals on the Kingston Bridge until we are convinced they are safe,' he said.
After the Palau collapse on 16 September 1996 - which killed two people - it emerged that the 241m span concrete box girder structure had been strengthened only three months previously. The technique used, running additional unbonded post-tensioning tendons inside the box girder, was similar to that proposed for Kingston. The specialist contractor responsible was also part of the same international group as the post-tensioning contractor at Kingston.
Kingston main contractor Balfour Beatty is already at least 17 months late on its £14M contract after major problems with software controlling 128 jacks under the main deck. These are intended to lift the deck, so that new piers can be constructed below, and move it 65mm south towards its original location.
But problems ensuring failsafe operation meant jacking was abandoned until at least September this year (NCE 5 February). Balfour Beatty now wants to tension 82 new tendons inside the box girder this summer, before lifting the deck, rather than after as originally planned.
'It was thought that the state of the rocker bearing on the northern pier made it dangerous to stress the deck before it was lifted and moved,' the Scottish Office spokesman explained. 'But now the bearing has been exposed, some believe the deck could be stressed earlier.'
Evaluating proposals will be difficult without information from Palau. Bridge experts are already warning that the collapse proves the accidental release of unbonded post-tensioning tendons inside a box girder liberates massive strain energy that can cause catastrophic damage to the main structure.
Palau government officials are currently considering a £10.6M out of court offer from the companies and consultants involved in the strengthening. A source in the US Department of the Interior suggested that non-disclosure of the results of the investigation might be one condition of the offer.
It is understood that the Scottish Office was initially kept well-informed on the progress of the investigation by the US government, which administered Palau as a trust territory until 1994. But since the Palau government launched claims for £60M compensation this information has dried up.