FASTER THAN expected completion of last weekend's lift of Glasgow's 52,000t M8 Kingston bridge deck has prompted engineers to reconsider traffic ban plans for the second stage of the jacking operation this Saturday.
It is hoped to halve the planned 35-hour weekend bridge closure and reopen the 268m long deck of Europe's busiest motorway crossing by Sunday afternoon, easing inevitable congestion.
'Even though last weekend's lift was one of the most complex of its type ever attempted, it went without a hitch and we allowed the bridge to reopen 17 hours early,' said Glasgow City Council engineering manager Ian Telford. 'Our only surprise was to discover that the deck is 2,000t heavier than we thought.'
The council is acting as the agent for bridge owner the Scottish Executive.
The 15mm lift was carried out by specialist VSL for main contractor Balfour Beatty Construction. The operation was needed to enable weak piers and bearings to be replaced. The £21M lift is two years late, following safety concerns about the computerised jacking system (NCE 21 October).
This weekend's repeat bridge closure will enable the deck, displaced by a tilting bridge pier, to be pushed 30mm back into position. To ease the push, a row of old pin bearings beneath a raised pier must be removed.
The task was expected to be tricky but, by Tuesday, half had been forced out and plans for an emergency night-time mid-week deck closure had been scrapped.
The deck, which will be held on 178 jacks for seven months while the piers are replaced, is being monitored by a network of 200 instruments recording every 0.1mm movement.