The bridges connect the differing levels of Nos. 1 and 2 New Street Square, built 15 years apart, both part of Deloitte’s central London ‘campus’
The two bridges, intended to be identifiable visual landmarks, link two client-facing areas at first floor level and two staff-only areas at seventh floor level, including the main restaurant.
The team of WilkinsonEyre with engineers Eckersley O’Callaghan came up with the design concept of a switchback ramp to take up the level change within the length of the bridges themselves, resolving accessibility requirements as simply as possible.
So each bridge has a three-way switchback ramp, combined with two flights of steps, and incorporate places to meet, work or just sit and enjoy the view.
The bridges are articulated as linked monocoque structures with stepped steel floors for greater strength and increased rigidity. Built on the ground, they were lifted into place in a single piece.
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The glazing of the bridge walls is also stepped for strength, allowing the glass panels to support the lightweight roof without the need for structural mullions. The roofs are formed from carbon fibre and incorporate skylights to improve the internal environment, while polished mirror on the underside of the decks distort views of the surrounding townscape. The principal external materials of glass and stainless steel were chosen to reduce the need for maintenance.
Timber is primarily used internally, and is intended to create a calm space, with light oak floor wrapping over the terraform surface and the ramps separated by a balustrade of slats of birch plywood, each individually lit. The ceiling is made up of individual slats of timber hiding ceiling-mounted services, while in-built worktops and seating are made of sub-lit blocks of Perspex fitted between the plywood slats.
Localised heating, cooling and ventilation is provided via a series of ‘trench’ units recessed into the floor of each bridge and positioned to help offset cold down-draughts and solar gains.
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We scratched our heads when faced with the challenge; the level change was too great to ramp over the road which suggested awkward ramps on the office floors or an unsightly platform lift, both of which would disrupt people flow, when the brief was to achieve a seamless connection. The solution came in a piece of geometry; a three-way ramp and two flights of steps; ensuring a step-free route as required.
As is often the way, the concept unlocked other design aspects; the floor plate became a monocoque deck rigidised by the folds of the ramps. Similarly corrugated glass façades supported a carbon fibre roof without the need for columns. Furthermore, the ‘landscape’ of the deck became an extension of the floor plate; with places to sit and places to perch with your laptop.
Giles Martin, director, WilkinsonEyre
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Start on site September 2018
Completion date December 2019
Gross internal floor area Lower bridge: 71m²; Upper bridge: 77m²
Form of contract or procurement route Traditional, JCT 2011
Construction cost Undisclosed
Structural/façade engineer Eckersley O’Callaghan
M&E consultant Hoare Lea
Lighting designer GIA Equation
Façades access and maintenance consultant D2E
Accessibility consultant David Bonnett Associates
Planning consultant Avison Young
Fire engineer Aecom
Structural engineer (1 New Street Square) HPM
Structural engineer (2 New Street Square) Pell Frischmann
Project manager Avison Young
Principal designer MLM Group
Approved building inspector GSA
Main contractor Overbury
CAD software used Rhino
Overall area-weighted U-value 0.856 W/m²K (link bridges)
Design life 60 years