A Scottish Parliament inquiry has concluded that the structural defects that led to the closure of the Forth Road Bridge last December could not have been foreseen.
The Infrastructure and Capital Investment Committee has also concluded that the Forth Estuary Transport Authority (Feta) decision to reprioritise projects within its capital plan following the Spending Review in 2011 – including work on the truss end link mechanism which failed – was an appropriate course of action.
Today’s report follows an inquiry called by the committee which heard from a range of witnesses, including structural engineers and representatives from Feta and Transport Scotland, in January and February.
MSP committee convener Jim Eadie said: “The closure of the Forth Road Bridge led to significant disruption and many legitimate questions have been raised about the nature of the structural problem and whether it could have been avoided.
“All of our witnesses were of the view that the defect which caused the closure of the bridge could not have been foreseen.
“As a result we have concluded that the decision by Feta to reprioritise the proposed work on the truss end links was an appropriate course of action on the basis of both the prevailing financial circumstances and the engineering advice available at the time.”
The committee concluded that the development of the Forth Replacement Crossing would have had an influence on decisions to reprioritise certain capital projects.
“The committee is of the view that Feta dealt with the challenge of reprioritising its capital proposals in a professional and responsible manner,” commented Eadie.
He commended all those who had worked hard to reopen the bridge ahead of initial estimates. However, he said that the committee was also conscious that the impact on the travelling public and businesses – particularly the haulage industry – was significant.
He added that the committee therefore intended to recommend that its successor committee in the new Parliamentary session gave consideration to exploring the issues further.
The enquiry also acknowledged that a previous report, carried out by consultant Fairhurst in 2008, set out results from an assessment that it had carried out on the connections between the stiffening truss and the main and side towers. This included the truss end links.
The Fairhurst report had shown that the welds connecting the bracket at the top of the truss end links to the main towers were overstressed under maximum traffic loading. However the enquiry findings published today said that the previous report “contained no indication that either the links or the pins – the seizing of one of which subsequently caused the defect which led to the December 2015 closure – were found to be overstressed.”
However, work based on the recommendation for total replacement of the problem truss end links made by Fairhurst was never approved.
Today’s report said that: “It is not clear to the committee exactly why the tender exercise was cancelled in early 2011, although it notes that both former Feta and Transport Scotland officials have indicated that it was due [to] affordability issues.”
The Scottish Government’s Forth Bridges Unit took over responsibility for the operation, management and maintenance of the Forth Road Bridge on 1 June 2015 after the dissolution of Feta.
The Forth Bridges Operating Contract was awarded to Amey in December 2014. The contract included the approach roads on both sides of the Forth from M9 Junction 1A at Kirkliston to M90 Junction 3 at Halbeath and will include responsibility for the new Queensferry Crossing when complete later this year. It will run for five years with scope for extending up to a maximum of 10 years.