The importance of carrying out bearing and expansion joint inspections by proficient and competent engineers who understand their functionality can often be key to maximising a structure’s lifespan and avoiding major, unexpected, emergency repair costs.
USL Ekspan have carried out a number of projects for swing bridges and foot bridges. From design, fabrication of all structural components, to trial erection and final installation. Details of these type of bridge installations can be supplied on request.
The A689 River Eden Bridge formed part of the Carlisle Northern Development Route (CNDR), a constructed 8.25 kilometre, 2-way single carriageway bypass road located west of Carlisle - built to provide a better transport link from West Cumbria to Scotland and the North East and relieve traffic congestion through Carlisle’s city centre.
The bridge crosses over River Eden to carry the A689 road, adjoining the CNDR’s new highway. Approximately 158 metres long, the structure is a 4-girder composite steel bridge deck supported on a central concrete pier and abutments. The central pier bearings, 4no BS5400 pot bearings of which 3 are free and 1is fixed, showed signs of wear and tear in varying degrees and locations. Further investigation was therefore required to assess the condition of each bearing and the remedial works required to ensure correct bearing functionality.
USL Ekspan’s Workscope
USL Ekspan were contracted by Balfour Beatty Civil Engineering to replace the central pier bearings. Prior to bearing removal an initial bearing inspection was undertaken for analysis of bearing defects, dimensions and approvals for bearing and temporary works design and to identify jacking locations for bearing replacement.
USL Ekspan’s inspection identified defects on each bearing such as vertical and diagonal cracking on the bearing plinth beams; vertical distortion to lower adaptor plates; over rotation and misalignment of plates and exceeded bearing transverse translation capacities. The conclusive decision to replace like for like all 4 BS5400 pot bearings was deemed best for the structure’s whole life longevity, rather than a part replacement where over time component parts functioning at different wear rates could potentially affect the bearing performance.
Prior to commencement, access to site via a dedicated track through boggy farmland had to be prepared. A 40-ton stone bund ramp was built and interlocking road mats installed, allowing clear plant and vehicle access.
Works on this project included: bearing inspection; bearing design and manufacture; design and installation of temporary works; design and manufacture of jacking stools; bridge jacking; removal of existing bearings and plinths; sequential installation of new bearings; reinstatement of bearing concrete plinths; de-jacking of bridge and removal of temporary works.
USL Ekspan successfully completed installation phases safely and to programme.
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