M180 Moor Road Bridge Partial Deck Replacement
Client: Aone+ (ASC for Highways England Area 12)
Works Commenced: April 2017
Works Completed: September 2017
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Moor Road Bridge was constructed in 1978 as part of the M180 scheme, linking the M18 near Doncaster to Grimsby on the east coast and providing access for major routes to Humberside Airport, Immingham and Hull.
Moor Road Bridge is a two span over-bridge concrete structure carrying the unclassified Moor Road over the M180. The bridge consists of precast, pre-stressed concrete beams composite with in situ concrete slabs supported on abutments and a central pier. Each deck spans 24.07m over the M180 carriageways.
In August 2014, Moor Road Bridge suffered from vehicular impact damage to its east elevation above the M180 westbound carriageway; part of the bridge deck was subsequently demolished for safety reasons. The width of the carriageway on the bridge has since been reduced to 4.0m, with a temporary vehicular restraint barrier and edge protection system on the east side of the bridge deck.
The Moor Road Bridge partial deck replacement scheme involved the replacement of the partially demolished bridge deck and the upgrade of the remaining existing road restraint system, over the bridge, to current standards.
Due to the complex nature of the re-construction work, Freyssinet was engaged in the Early Contractor Involvement process.
The scope of the Works included:
- Pre-casting of the replacement beam and cantilever slab as a single unit off site. The replacement pre-cast section had to replicate both the vertical and horizontal profile of the original structure.
- Re-alignment of the temporary Varioguard vehicle barrier on the Moor Road to provide safe working area.
- Installation of additional Combisafe edge protection to the remaining existing deck, in order to provide a safe environment in which to undertake the works.
- Scaffolding over the M180 westbound verge/embankment. This entailed geotechnical investigation and foundation design, a temporary works AIP submission and the design and check of the scaffold itself.
- Design and installation of a temporary restraint system to the existing bridge beam (retained beam 2) prior to the commencement of hydro-demolition in order to maintain structural integrity during the reconstruction process. Wedge-jacks were used for this purpose, and were found to be an effective and practical solution.
- Hydro-demolition of part of the existing bridge deck slab to provide an adequate length of existing reinforcement to stitch to the reinforcement of the replacement precast deck unit. This process involved the design of a suitable hydro-dem enclosure to fully contain the debris.
- Preparation of the existing bearing plinths, on top of the south abutment and central pier, to receive the replacement bearings and precast deck unit.
- Installation of the replacement bearings to the line and level of the new precast beam section.
- Delivery/installation of the replacement precast deck section. This process involved a full weekend closure of the M180 to facilitate the 500 tonne crane used to lift the 70 tonne precast beam section.
During the precast beam installation process, temporary restraints were installed in order to tie the replacement precast deck unit back to the existing deck slab. The restraints were designed and fabricated specifically for the scheme.
Once the beam had been installed to line, levelled and stabilised using the restraint systems, temporary formwork was installed between beams for stitching the deck slab between the precast unit and existing slab. This formwork system was designed specifically for the Works and was installed during motorway closures from a scissor lift, as access from above was restricted by the existing reinforcement.
Reinforcement was then fixed and concrete poured during night time closures of the M180 motorway.
Following the necessary curing period, the formwork was removed and the deck waterproofed before kerbs and surfacing work was undertaken, and expansion joints were replaced. The existing road vehicle restraint system (bridge parapet and safety barrier) was removed and replaced.
After the re-construction work, Moor Road Bridge will be returned to its original state prior to the bridge strike, and will fully re-open for public use in September 2017.