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Analysis | Forth Road Bridge points to maintenance challenges

Analysis bridges

In among all the noise surrounding the nightmare problems to hit the Forth Road Bridge in recent weeks appeared one particularly frustrating tidbit.

Engineers had five years previously recommended total replacement of the problematic truss end links. Yet no such work was undertaken.

The works, set out by consultant Fairhurst, were never approved. The operator feared the required long closures and hedged its bets that work could be held off until the new Queensferry Crossing opened – scheduled for the end of December.

But, as if to prove it was creaking at the seams, the 50-plus year old road bridge showed one crack and then a second, forcing the bridge’s total closure. Engineers scrambled to make inspections and come up with a longer-term fix.

The words ‘false economy’ spring to mind. And what is confusing is that despite work that Fairhurst carried out, and despite strengthening plates attached to highly stressed sections a decade ago, the first crack came as a surprise to the maintenance team, the section having previously been assessed as not highly stressed.

It goes to highlight the complexities of managing an aging asset – even one where its limitations appear to be well understood. But what are our expert engineers to do about those assets whose condition is less well understood?

And we’re not talking about in far-flung places, with questionable governments.

A report in 2014 by the American Road and Transportation Builders Association found that more than 63,000 bridges across the US were in urgent need of repair, with most of the compromised structures featuring on its major highways.

In the UK, an RAC Foundation report two months ago revealed that over 2,000 road bridges on mainland Britain were not fully usable – some were built to old design standards, while others had deteriorated through age and use. The body estimated that it would cost £328M to bring them all up to perfect condition.

The overwhelming scale of work needed and the cost is no doubt a prohibitive factor in the problems being dealt with overnight. But reactive repairs to prevent a significant failure are almost always more expensive.

Engineers have a tough gig. Their role is too often reactive and there is a limit to their capacity to get ahead of all of the threats – even when the clients are ready and willing to commission their expertise.

And the challenge is growing. As a senior executive running one of the world’s most esteemed engineering firms challenged us recently: New Civil Engineer must ask what our industry’s plans are for solving the looming threat to the world’s suspension bridges. How is it going to be possible to replace the multiple critical cables and ensure the longevity of such structures can be preserved? A threat and one he believed none of the best engineering minds had yet even begun to resolve.

So the gauntlet has been laid down – can engineers head off disaster with exceptional asset management skills and make sure the people holding the purse strings sit up and listen to their advice?

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