This was a particularly challenging underbridge reconstruction due to the extremely restricted access to the site. The bridge is located in the bottom of a steep sided valley, with access at the toe restricted by the river, and only a narrow single track lane leading down to the site, unsuitable for heavy goods vehicles. The reconstruction also took place during a particularly cold winter, with over 6 inches of snow on the ground during the critical works.
- A cantilevered scaffold was attached to bridge pier of the existing structure, accessed via a “bridged” scaffold to the opposite pier. Walkways were also extended around the piers to gain access from above for the use of site personnel.
- Removal of the existing cast iron and steel bridge deck. This was lifted out in five sections by a 125ton Kirow rail mounted crane and taken clear of the site to be cut up for loading on to rail wagons for recycling.
- Reduce level excavation and cast new insitu concrete impost bases.
- The new steel bridge beams were then craned in using the Kirow crane.
- Pre-cast concrete deck units installed on to the new bridge beams.
- Water proofing to bridge deck.
- Install new hand rail and safe access system.
- Existing stonework was then reduced as indicated above to accommodate the new reduced width bridge deck which was “sunk” into the stonework and situated on a concrete pad on either abutment. Stonework was then suitably reinstated.
- The track superstructure was then reinstated over the new structure.