24 February 2006
24 February 2006
The third phase of strengthening West London’s extremely busy Hammersmith Road Bridge, has just been initiated by refurbishment Contractor Concrete Repairs Limited (CRL).
The 105 years-old, three-span structure, which carries traffic over two Network Rail and one London Underground railway lines, is located on the A315, close to Olympia. Originally constructed with thirteen longitudinal cast-iron girders per span, supported by brick and piers, the bridge is currently well below the required capacity for accommodating 40-tonne vehicles. As a result, restrictions to both the number of lanes on the bridge and vehicle weight limits have been in place, which was an unacceptable long term situation given the traffic volumes being carried by this bustling thoroughfare.
Because of the massive disruption that would be caused (to say nothing about the financial implications), the construction of a replacement bridge was simply not an option. Neither was the installation of a steel/ composite alternative, since the solution needed to be both as light in weight as possible and quick to install.
Several alternative methods were considered, but the method finally chosen was the installation of carbon fibre reinforced polymer (CFRP) plates, a technique that has been employed on nearly four hundred sites over the past ten years in the UK. A bespoke design was produced by Mouchel Parkman Advanced Engineering Group and independently checked by Tony Gee & Partners. It demanded specialist design and installation but in comparison to steel plate bonding, the CFRP system offered several advantages. Unlike steel it will not corrode, is considerably stronger and will not confer significant additional dead load to the structure. It is also easier to install due to its lightweight nature.
The installation work was procured by The London Borough of Hammersmith and Fulham through their term contractor Colas. Specialist installer CRL is bonding the plates to the lower flange of each beam, using a two-part cold-cure epoxy adhesive. No additional mechanical fastening is employed. The contract is being undertaken by CRL under tight programming conditions to meet specified and very limited rail closures. Intensive preparation and professional management has ensured that the work has proceeded to programme.
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