EXPERTS called to give evidence at an inquiry into the closure of the Forth Road Bridge have agreed that the problem defect would have been difficult to foresee.

The bridge was forced to close for almost three weeks in December after a 20mm crack was discovered in the steelwork, causing transport chaos as commuters were forced to divert via Kincardine or brave heaving public transport.

Last month, the Scottish Government launched an inquiry into the closure and has been probing experts on the structural defects identified on the bridge and whether these could have been avoided or dealt with differently.

At a meeting of the infrastructure and capital investment committee last Wednesday, members were told that it would have been difficult to pick up on the failure before it happened.

Peter Hill, general manager and bridgemaster with the Humber Bridge Board, said: "If we monitored every single element and joint, it is possible that a detailed analysis of the information from every point of the bridge could give some indication of some trouble in some part of the bridge, but that would be a huge exercise.

"The amount of data mining that would be necessary to give the information that would point us to a specific element causing distress would require a very large team of people looking at the results 24 hours a day. That might be possible but it is probably not practical or economically viable."

Richard Fish, an independent engineering consultant, added: "It is difficult to divorce hindsight from all this, because we know what happened and are trying to wind the clock back a couple of months to assess whether what happened could have been anticipated and avoided.

"We can say with hindsight that that should have been examined and that some analysis should have been done to assess the loads in the end posts on the truss. However, the irony is that the Forth Road Bridge is one of the most well-managed bridges in the whole United Kingdom. I have a huge regard for Barry Colford, who had such a thorough understanding of the bridge. It seems unlikely that something would be overlooked and I would have thought that, at the very least, those issues would have been addressed."

John Evans, consultant at Flint & Neill Ltd, agreed with his fellow experts and said: "If the pin jams up and there are internal stresses on the connection between the fabricated bit and the pin, we get no evidence of that. What happens is that an imperfection—I will not call it a defect—becomes overstressed and we can get a sudden failure, which transfers quickly across the weld line and into the material. My experience is that we would not find such a failure until it was there.

"I suspect that the failure happened between the two inspections—the inspection in May and the inspection when it was picked up, in early December. Because of the nature of steel, when an imperfection starts to grow, it grows very quickly."

Mr Evans also praised how quickly a solution was put in place and added: "I am absolutely confident that the work was a remarkable achievement. I have come into this only since the event and I have been following what has been going on. The fact that all 16 end links were dealt with in that time, in difficult conditions in the middle of winter in the middle of the Forth, given the problems with the old steel that we have discussed, makes it a remarkable achievement."