ACCIDENT INVESTIGATORS in Bangladesh are still trying to discover why nearly 5km of 750mm diameter gas pipeline ripped away from the new Jamuna Bridge on 11 June, less than two weeks before the official opening.
Bangladeshi sources said the gas main was being filled with water in preparation for hydraulic pressure testing. The main, which was suspended under the concrete box girder bridge deck, broke away along the whole 4.8km bridge and disappeared into the river, which is now in full flood.
Exactly why the pipeline's supports failed remains unclear but local press reports have alleged that the main cause of the collapse was a failure to allow for the weight of the water in the pipe during testing.
Joint venture supervising consultant High-Point Rendel, NEDECO of the Netherlands and Bangladeshi Consultants immediately launched an investigation into the accident, supported by a High-Point Rendel team which flew out from London next day.
After an initial inspection, which apparently showed no significant damage to the box girder, the bridge was opened by Bangladeshi prime minister Sheikh Hasina on 23 June as planned. A High-Point Rendel spokesman said this week that the joint venture was still waiting for a report on the incident from main contractor Hyundai.
The £154M crossing was built to an alternative design drawn up by Hyundai's San Francisco-based structural engineer TY Lin, rather than one of the two design options produced by the joint venture (NCE 18 June). High Point Rendel this week refused to confirm that the JV had retained responsibility for checking TY Lin's design.
But sources close to the project suggested the checks were actually carried out by Glasgow-based Cadogan Consultants, acting as subconsultants to the JV. Cadogan director Rod Wilkie would say only that Cadogan representatives were now in Bangladesh.
However TY Lin senior principal Mirek Olmer said that the practice's calculations had been checked by the JV several years ago but said that there had been no contact between his office and Hyundai since the collapse.
Olmer added: 'We designed the brackets and anchors, not the pipeline itself, but without more information from Bangladesh I can't comment further.'
Officially dubbed the Bangabandhu Jamuna Multipurpose Bridge, the structure is designed to carry 232kV power lines, a metre gauge railway and telecommunications links as well as road traffic and the gas main. The bridge is the first fixed link across the Jamuna river which divides Bangladesh in half.
River training works costing another £167M were carried out by HAM-Van Oord to keep the normally unpredictable Jamuna in one channel under the bridge.
High-Point Rendel said last week: 'The gas pipeline was not intended for immediate use. It will take future gas supplies across the river once the land infrastructure is in place.
'It is anticipated that restoring the pipeline and subjecting it to the rigorous testing programme will not in practice delay the supply of gas to the western zone of Bangladesh.'