A £10m Transport Scotland investment package to replace nine bridges along the A830 has seen contractor Bear Scotland shift to using stainless steel reinforcements.
Speaking to Transport Network, Richard Cook, scheme delivery manager for Bear Scotland, said it was the first time the company had used stainless steel reinforcements throughout the whole of a bridge.
He added they would be using it throughout each of the further eight replacements and 'as much as possible' in the future.
The first of the nine structures to be replaced by Bear Scotland was the new Dearg Bridge west of Glenfinnan, where final reinstatement was completed early this year. Bear Scotland will now move on to replacing the next bridges at Garbh and Utha with works due to begin this spring.
Mr Cook said: ‘In the Dearg Bridge, we used stainless steel reinforcement instead of normal carbon steel. We have used stainless steel in parts before but I think this is the first time we constructed a whole bridge using it.
‘As a result the bridge should not need any maintenance to its concrete throughout its lifetime. As its stainless steel you don’t get issues of corrosion of reinforcement and swollen concrete.’
Mr Cook added: ‘We will definitely be using stainless steel on all the other eight bridges and as much as possible in the future.’
The Dearg Bridge has been built to last 120 years and replaced the old structure with a new 6 metre wide carriageway, 1 metre hard strips and 1.5 metre verges and masonry parapets.
Bear Scotland used recovered stone from the old bridge to help the design blend with its Highland surroundings.
Mr Cook explained how the project expanded in scope after initial plans were limited to basic road safety improvements.
‘The A830 route didn’t have a very good safety record and there was quite a lot of pressure from local communities. The Government made a commitment to improve the route. So there was a series of works to provide additional signage, lighting and high friction surfacing. But they also made the commitment to improve vehicle restraint systems along the route, including safety barriers and the upgrading of these nine bridges,' he said.
‘Initially it was a vehicle restraint improvement project but when we looked at the bridges they were all sub-standard. The carriageway width was narrow, and all the safety barriers were sub-standard.
‘In trying to improve the vehicle restraint systems it escalated from there and we looked into widening and strengthening but when we looked at the structures they weren’t really suitable for that so it has evolved into these bridge replacement projects.’
The Dearg Bridge project also saw a new system applied when a temporary bridge was used to prevent any traffic delays.
Mabey Bridge was employed to install the temporary bridge for the project. They constructed it from its component parts adjacent to the watercourse on a temporary road and then used a crane to lift it into position over a period of four or five days.
However when it came to removal, the subcontractor TSL removed it themselves in two days using a temporary propping system.
‘It’s a panel bridge of six panels so they split it down into the six panels rather than right down to component parts. It was a lot quicker and cheaper to do that than bringing a crane back on site,’ Mr Cook said, adding that this system was likely to be employed on the other eight bridges too.