Waterloo International Terminal
Waterloo Station, London
YRM Anthony Hunt Associates
Sir Alexander Gibb & Partners
1991 - 1993
photo Jo Reid and John Peck, courtesy Grimshaw
Waterloo International Terminal opened in 1993, heralding a new phase of rail travel in the UK. Built adjoining the existing mainline station, it was designed as the first London passenger hub for the Eurostar rail service using the newly completed Channel Tunnel.
The new station became a London landmark and a symbol of modern engineering. Its most striking feature is the 400m long roof that runs the entire length of the curving platforms, across the width of five new rail tracks.
The roof is a series of steel flattened arches that together hold more than 2,520 panels of glass. These overlap to accommodate both the longitudinal curve and the arch itself. However, spectacular as the roof is, 90% of the £120m budget was in fact spent on the lower level structures. Ticketing, security, passport control, waiting and concourse areas, arrivals and departures — all are accommodated at lower levels
Existing brick vaults below the station were repaired and improved, and a new, reinforced concrete box was built as the foundation of the new building, and to provide carparking space above the existing London Underground lines. On top of this, five two-storey viaducts carry the new rail lines and the 800-tonne trains, and must also bear their braking force.
The five viaducts are supported by a grid of cylindrical concrete columns that rise up from the carpark level, through the circulation levels to the platforms. A structural glass wall separates old Waterloo Station from the new.
However, it's the train shed roof that's the undoubted star. It comprises 36 three pin arches of spans varying from 32.7m to 48.5m. It curves in two directions, narrowing towards the far end. This allows for wider platforms closer to the station entrance/exit, where passenger density is greatest. The curvature of the roof is steeper on the western side and here the trains pass close to the structure.
The arches are made up of two dissimilar curved trusses, triangular in section, with compression booms of tubular steel (CHS) and tension booms of solid steel. The arches are asymmetrical, with the longer sides to the east, supporting solid roof areas. This disposition meant the eastern trusses needed two compression beams on their outer sides, with a single tension boom below. This results in horizontal thrust through the pin joints to the shorter trusses on the west side.
The bending moment patterns are reversed in the shorter trusses, where single compression booms are required on the inside and a pair of tension booms on the outside. The diameters and wall thicknesses of the compression booms vary in accordance with the bending moments, with the smallest measurements close to the pin joints. This was achieved by telescoping one tube into another, and slitting tubes and rewelding them to form tapers during fabrication.
Truss dimensions and configurations vary with bending moment requirements too. The trusses are deeper and wider at the centre of the spans. Both compression and tension members are curved — structural engineer Anthony Hunt described the trusses as "banana shaped". Curved, tapering trusses were later used to great effect at Galpharm Stadium in Huddersfield.
A secondary tubular steel structure provides line bracing between trusses and supports the cladding and glazing. This structure is in turn cross-braced by steel tension rods with forked connectors design of which was derived from yacht rigging components.
The roof glazing is held in place by aluminium sash bars, slotted to reduce their weight. On the western side, the glazing has a transverse pitch, directing rainwater to collection points at the bases of the trusses. The solid areas of roof cladding consist of stainless steel panelling, laid in a herringbone pattern and attached to the outside of the trusses. The pattern is an echo of the rhomboid shapes that allowed flat panels to form a curved plane at the Great Conservatory at Chatsworth House (Decimus Burton and Sir Joseph Paxton). The steel-clad areas too are pitched.
The train shed is an impressive piece of design, one that pays homage to the engineering of the railway age. Hunt's experience with using a few varieties of batch-produced structural components to achieve a complex result really shows here. The structure is unitised but not uniform. The logical rectilinear structural grid accommodates a complex, snaking tapering plan-form.
In 2008, the Channel Tunnel to central London section of the high speed rail link was completed. This line uses the new terminal at St Pancras Station, rendering Waterloo International Terminal obsolete. A new use will need to found for the structure that delighted rail passengers for just 15 years.
Architect: Nicholas Grimshaw & Partners
Quantity surveyor: Davis Langdon & Everest
Services engineer: J Roger Preston & Partners
Main contractor: Bovis Construction
The Architectural Review, Vol CXCIII No. 1159, September 1993