London Underground Limited – carbon fibre bridge strengthening project
Pipe Crossing PC44 is an underline bridge that supports the District & Circle line. The cast iron troughs that support the tracks gave cause for concern in that they could fail without warning due to severe corrosion.
Clancy Docwra installed 84 innovative carbon fibre plates to strengthen the underside of the crossing ensuring long-term structural integrity.
Initially the structure was grit blasted to remove the de-laminated cast iron and prepared to a SA2.5 bare metal standard. The carbon fibre plates were then applied to the structure using a high strength resin and held in place between shifts to cure using a jacking system.
Challenges: Access to PC44 was difficult as it was via the tidal-affected Fleet Sewer that was only accessible by either side entry manhole on Bridge Street or a shaft manhole on the green outside Blackfriars Station. With access hindered by the River Thames tidal flows, works had to be planned to coincide with low tide. Access into the sewer was classed as a high risk confined entry which meant that all operatives had to be NVQ confined space trained and passed as medically fit to complete the works.
Key Achievements & Innovation: This project was delivered on time and on budget by Clancy Docwra. The end product is a structure with an extended design life that reduces expensive and dangerous cycical inspections and represents value for money for client and taxpayer. Not only did the chosen delivery method cause no disruption to the underground system, but there was only minimal disruption to the road users.
The success of the scheme was recognised by the Institute of Civil Engineers (ICE) Civil Engineering Awards 2014 as a nominated project and received a ‘highly commended certificate’.
Client: London Underground
Completion: December 2013