Some heavy goods vehicles (HGVs) are to be allowed back onto Scotland’s Forth Road Bridge for the first time since a structural problem was found in early December.
The bridge was closed to all traffic following the discovery of a fracture in a key load-bearing steel element. It reopened to buses and vehicles under 7.5 tonnes a few weeks later; the structural monitoring system shows that a limited number of HGVs can now be allowed to cross.
The phased reintroduction of HGVs is due to begin tonight, with up to 600 allowed to cross northbound in a five hour nightly period, subject to weather conditions.
Relaxing the current HGV restrictions during the night is intended to help to mitigate the impact of the closure, without causing over stressing of the structure. Traffic signals will release HGVs on to the bridge at a rate of one every 30 seconds. The release rate has been calculated by engineers as the optimum to maximise the number of vehicles able to cross whilst minimising the impact on the structure.
The structure will be monitored throughout the process to determine whether the number of HGVs being allowed to cross the bridge can be increased.
Information from the bridge monitoring systems has shown that the second phase of the repair work to strengthen the bridge needs to be completed in full to the main span locations before the bridge can fully reopen to HGVs. Recent high winds have led to closures of the bridge to all traffic and have limited the opportunities to carry out the second phase of the repairs but the bridge is now scheduled to be fully reopened to HGVs with no restrictions by mid-March.
Chartered engineer and Amey’s account director for the Forth Road Bridge, Mark Arndt, said: “During the recent storms, the bridge has been closed to traffic, at times, because wind speeds have been so high and it wouldn’t be safe to have people out working in those conditions. Our teams are working flat out to complete the work necessary to fully reopen the bridge but our timetable is highly dependent on the weather and our priority has to be on safety.”
A video of Arndt talking about the repair work is in Bridgeweb's video section.