DELAMINATED SURFACING on London's troubled Hammersmith Bridge is being investigated just six months after the entire carriageway was relaid.
The polyurethane based antiskid thin surfacing has broken up in several places on the bridge deck but so far engineers from the London Borough of Hammersmith & Fulham have been unable to identify why.
The current three month bridge closure, required for repairs to last month's bomb blast (NCE 6 July), is being used to tackle the latest problems and repairs should be complete before traffic is allowed back on the bridge at the end of August.
Resurfacing work was carried out as part of the bridge refurbishment by specialist contractor Makers and completed in December last year. The work involved bolting 850 steel plates to the bridge deck and then applying the 7mm thin surfacing layer. Problems with the latex backing on the steel plates originally caused delays reopening the bridge (NCE 11 November).
The current problem, which has occurred within the contractors' defects liability period, appears to be caused by a breakdown in the bond between the steel plates and the thin surfacing. Delamination - the largest area being around 3m 2- has occurred mainly at the joints between the plates in the centre of southbound lane, rather than in the traffic wheel paths.
'We don't know if we will have to relay the whole deck, ' said director of Highways at Hammersmith & Fulham Roger Khanna. 'In some areas it hasn't stuck.'
Before laying, the decking system was tested at Imperial College and on a experimental section of the bridge, where it was trafficked for 15 months.