Bidston Bypass North Bridge
Bidston Bypass North is a three span composite structure carrying the A554 (Bidston Link Road off the M53) over the main West Kirby to Birkenhead electrified railway. In addition to the railway line the bridge also spans a masonry culvert carrying the River Birket under the railway, a cycle path and pedestrian walkway connecting the nearby Bidston Rail Station to a Tesco superstore. A nature reserve, golf course, small housing estate and retail park are also in close proximity to the structure. The bridge is 121m long and 19m wide comprising of 4no steel box girders and two 300mm concrete decks.
The works included :
- Installation and maintenance of temporary traffic management
- Localised concrete repairs to the soffit of bridge deck and installation of hybrid galvanic cathodic protection
- Replacement of joints, kerbs and drainage units
- Replacement of sealant to box girders, expansion joints and abutments
- Repairs to parapet
- Repainting of internal and external box girders and bearings
- Liaison with relevant statutory bodies, Network Rail and local businesses
Eric Wright Civil Engineering held a Principal Contractors Licence and organised possessions to facilitate the works. Works were undertaken during normal midweek hours from fixed design scaffold approved by Network Rail and during weekend night possession and isolations from a combination of tower scaffold and cherry pickers. We managed the liaison process with Network Rail from inception and undertook the temporary works designs and submissions in accordance with Network Rails Forms 001 to 003 procedures. Re-painting works to the areas of the bridge over the live tracks were undertaken using a combination of methods, including access towers and MEWP’s in order to maximise productive possession works.
Corrosion Protection System
A corrosion protection system was installed to provide protection via both hybrid and electrochemical treatment to generate a passive environment around the steel reinforcement and sacrificial anodes places around patch repairs to protect the adjacent steel from corrosion initiation. Duoguard 500 hybrid anodes were installed located either side of the longitudinal joint in the soffit and around water staining to the abutments and Patchguard sacrificial anodes located around the periphery of patch repairs.
A comprehensive Quality Management Plan and Inspection and Test Plan was developed incorporating the specialists Quality assurance testing and monitoring regimes. There was approximately 1000 anodes/cathodes installed and 350m of cabling across the structure. EWCE directly oversaw the installation and testing of all of the above within the contract period.
Hydro demolition was used to remove defective concrete for repair. Given the presence of a sensitive receptor immediately under the bridge, we employed Siltbuster and their innovative concrete wash water unit to manage the waters, allowing the discharge of excess to nearby grass land as consented by the Environment Agency .
Preparation of external steel box girders and bearings was grit blast to SA2.5 standard. Network Rail approved coating system M24-049 Epoxy/Polyurethane was applied consisting of full primer coat, stripe coat, intermediate and finish coat with a polyurethane sealant used for joints and gaps.
A Paint Inspector was present throughout the works to record all soluble salt tests, environmental readings and wet and dry film thickness records.
EWCE were integrally involved at the early post award stage with the client team and suggested alterations for the benefit of the project, namely; An alternative mechanical preparation method and paint system was proposed for use in the confined space of the internal box girders in lieu of the originally specified system which necessitated grit blasting internally. EWCE were concerned over the H&S aspects of this operation and their alternative proposal which yielded the same design life was accepted. Works were undertaken by fully trained confined space ICATS trained operatives, and a dedicated safety rescue team was on site throughout these works.
The original scope of works called for a contractor designed modification to the existing access hatches into the box girders. EWCE recognised that this was a high risk item with associated complex design and effect on the existing box girders. EWCE successfully demonstrated that the hatches did not need to be modified and had no undue effect on the H&S of operatives working in the box girders. The works were subsequently omitted and the savings apportioned accordingly.