Balfron Bridge on the A81 was closed in September 2016 after the arm on an earth mover, which was being transported by a heavy goods vehicle, struck the bridge between Balfron Railway Station and Ballat crossroads. The structure holds seven mains water pipes which carry water from Loch Katrine to Glasgow. As a result of the collision, the bridge required additional supports. Various repair options were considered before the decision was made that the existing bridge should be removed and a complete new structure installed. The new bridge would be designed and built to match the style and appearance of the existing structure with riveted connections.
Millar Callaghan were awarded the contract to fabricate and install the new bridge structure. After a full site survey of the existing steelwork, our fabrication department went into full production on the new bridge. Removal of the old bridge took place whilst this fabrication was being carried out, with the water pipes being supported from the ground up to ensure that the supply of water to Glasgow was not affected by the works.
On completion of the shop fabrication a full trial assembly took place at our Irvine workshop, before the completed structure was disassembled and sent for blasting and painting to a full highway specification. Whilst the main structure was being painted, our engineers and installation team positioned the fourteen new bridge bearings onto the new bridge abutments. The new sections were then assembled around the water pipes and the temporary pipe supports. When the bridge was fully assembled and resting on the new bearings, new pipe support hangers were installed to support the weight of the seven water pipes. With the new pipe hangers in place the temporary supports could be removed. In addition to these works, a 17-tonne collision protection barrier was installed in front of the bridge to prevent any similar bridge strikes in the future.
