Strengthening of bridge foundations and abutments in Essex
Constructed in 1925 and comprising a reinforced concrete monolithic structure using the “Hennibique” system with three clear spans of 4877mm, Langford Bridge carries the increasingly busy B1018 between Hatfield Peverel and Heybridge over the River Blackwater at Maldon.
The structure was found to be incapable of sustaining 40 tonne loading due to insufficient strength in the transverse pier beams. Additionally, a further investigation established that the bridge foundations were being undermined by serious river scour.
Working for their client Essex County Council, Mouchel Consulting Ltd identified five options to resolve these issues, and proposed one which minimised construction hazards, excessive disruption, legal constraints and undue costs whilst minimising the key stakeholder objections.
The proposed cost -effective option had the benefit of keeping two lane traffic flow during the remedial works which were planned to take 23 weeks.
The main contractor Alfred McAlpine Asset management Services subcontracted all works except TM to Topbond plc Group.
Topbond completed the following works:-
• Replacement of the original reinforced concrete apron slab with a substantial reinforced concrete raft foundation.
• Construction of new reinforced concrete abutment lining and intermediate corbelled pier walls.
• Strengthening of the existing bridge deck with a combination of longitudinal parallel flange channels and transverse universal beams bearing on the new abutment walls and pier walls.
Several novel working methods were required to complete works within the height restrictions under the bridge. Successful communications and a pro-active relationship between Mouchel, Alfred McAlpine and Topbond was established throughout the project. This allowed prompt resolution of the unexpected – in particular, the various obstructions and voids encountered during removal of the existing riverbed and concrete apron and abutment works, which required decisive agreements on design and method changes. This approach minimised delays without compromising original design requirements.
Consequently, the project was completed to the satisfaction of all key stakeholders.