Grimshaw’s reorganised London Bridge station is unified by a street-level concourse larger than the pitch at Wembley

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Rick Roxburgh

Historically, London Bridge has been confusing for passengers to navigate, especially those less familiar with the station. Not least of the reasons for this was the division in access to the through tracks and the terminating platforms.

London Bridge is the fourth busiest station in the country, and the cornerstone of the Thameslink improvement project, the main line that runs from Bedford to Brighton through the City. While providing additional capacity for around two thirds more passengers to use the station, the redevelopment scheme has had to ensure that this major interchange forms seamless and sympathetic connections with the neighbouring infrastructure of underground station, bus station and streets. The experienced team, including architect Grimshaw, has worked together to achieve what it regards as a new station typology.

Thanks to a complex reconfiguration of space, in particular amendments to the tracks, 80 per cent of Thameslink’s capacity will be unlocked to help develop more connections between the north and south of the UK. The five year redevelopment, due for completion in summer 2018, has required extensive coordination to ensure that the final design unifies the site. A new concourse, bigger than the pitch at Wembley, has been built beneath the tracks at street level and is now in use. The number of terminating platforms has been reduced from nine to six and the number of tracks going through the station is being increased from six to nine.

The 15 tracks and platforms span the new concourse via 29 bridge decks, comprising steel plate girders typically 970mm deep by 600mm wide. These form a composite deck with a 250mm reinforced concrete slab. Unusually, the steel girders have been encased in concrete to give enhanced acoustic performance on the concourse below. Weathering steel was used for the exposed bottom flanges to eliminate the need for maintenance painting.

The bridges are designed to take LM71 loading, in accordance with Eurocodes, and a Kirow KRC1200 rail-mounted crane, which weighs 116 tonnes unladen. The reinforced concrete columns and crossheads were formed with prefabricated reinforcement cages which were temporarily supported on a sacrificial steel dolly.

The design of the bridge decks involved close coordination. Midspan deflections of up to 40mm have an impact on platform and canopy designs, and required pre-assessment of the serviceability of the materials to be used. Bridge deck loads have had to be compiled quickly to enable the buttress mini piling designs to progress to AFC Issue. This has included rail structure interaction analysis using LUSAS software to model the traction and braking effects transmitted through the rails to buttress and column foundations. Drainage and services running both along the tracks and transversely had to be carefully coordinated, while liaison between the civil engineer and architectural team helped ensure the crossheads could carry the pot bearings whilst retaining their aesthetic character.

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