Heathrow T5 Techspan Arch (Oct 2001 - June 2003)

Location: Terminal 5, Heathrow Airport, London, United Kingdom
Owner: British Airports Authority.
Client: Freyssinet Group
Value: GBP 600000 (approximately R 7million)

Description: As part of the new Terminal 5 Development at Heathrow Airport, an access tunnel under the so called Welcome Roundabout was required.
The tunnel was constructed using the TechSpan system, a proprietary product of the Freyssinet Group.
It is a tri-articulated system in precast concrete, with the points of articulation being at the foundations and at the crown. It is an adaptable product, whereby it is cast in adjustable moulds so that the profile of the arch can be tailor made to a particular application i.e. it is not a catalogue system with a fixed set of profiles. The profile of the arch is generally a funicular curve, resulting in minimised bending moments. The analysis of TechSpan structures is carried out by means of specialist 2-dimensional finite element software, whereby all construction stages and working conditions are analysed, whilst taking accurate account of soil structure interaction. Design of the concrete sections is in accordance with BS5400.

Services Provided: Exstrado was responsible for the detail analysis and design, layout and reinforcing drawings for this 135m long TechSpan structure, with a span of 17.150m and a rise of 7.14m. The structure comprises 350mm thick elements on spread footings, and is characterised by symmetric truncated ends. Stability of the truncated ends is achieved through fixity of the units at the base and a ring beam connecting them at their apex line.