A90 Finavon Bridge

Tender description

The A90 Finavon bridge is a three span structure spanning over the River South Esk and consists of a pseudo-slab deck of inverted prestressed concrete Tee beams and in-situ reinforced concrete infill. The beams bear onto concrete abutments and two intermediate piers founded on shallow spread foundations. The A90 520 South Esk Bridge is a simply supported single span composite deck consisting of in-situ reinforced concrete on two weathered steel plate girders. The deck is supported on reinforced concrete abutments with spread footing and return cantilever wingwalls. The retaining wall supporting the farm underpass access at the north abutment of A90 510 Finavon Bridge failed during Storm Babet in October 2023. Emergency works are currently in place to provide stability to the structure. The emergency works, immediately post-storm, included infilling the undermined section of the north abutment with mass concrete and placing rock bags and rock mattresses in the riverbed to raise the riverbed to acceptable levels. 2-tonne rock bags were also placed on the northern footpath to provide a surcharge to the north abutment to satisfy the geotechnical bearing pressure checks. Due to the failure of the footpath, traffic restrictions on abnormal loads (SV150 & SV196) were put on the bridge. The aim of this project is to provide stability to the existing structure, prevent future scour damage and allow for the removal of the abnormal load restrictions. The proposed scoping includes the installation of a secant piled wall with reinforced concrete pile caps at both the north and south channels under A90 510 Finavon Bridge and to provide stability to the abutments, as well as protecting from scour under both structures A90 510 Finavon Bridge and A90 520 South Esk Bridge, during future storm events. The secant piled wall will also allow for the footpaths to be reinstated with mass concrete to provide additional surcharge. To protect the riverbed and mitigate any future scour to the structure, concrete mattresses will be installed along the entire riverbed area, including the underside of the A90 520 River South Esk bridge