O2 Link Bridge, Slough Berkshire
Client: ISG InteriorExterior PLC
Engineer: Adams Kara Taylor
Architect: TP Bennett LLP
Value: £1.3m
Period: December 2008 - April 2009

Description:

This project was for the supply and installation of a feature link bridge between the new head office and existing offices for O2 in Slough Berkshire, with the head offices remaining operational for O2 throughout the onsite works.

The initial design was for simple "V" support CHS columns to the bridge deck, following design team meetings the final design comprised of complex "tree" CHS columns the majority with double branches whilst the main two at the east end having 4 branches, none of the columns are vertical the angles in both directions differ for each set of columns. The 4 branch columns ending up weighing 9t as an assembled unit.

The design and selection of the column CHS sections was made harder by the use of smaller CHS sections for the lower portion and larger CHS sections for the upper sections of the columns. The aim and criteria here was that the end product onsite for the columns had feature shapes to their lower sections whilst looking the same diameter up to the upper side of the bridge.

The head of every column had very large moments and in order to accommodate these GWS designed sections of the main bridge floor beams as plate girders to allow the connections of incoming members as the 914UB's designed by the engineer failed at the connection points, these were fabricated as part of the upper CHS column. This made for challenging detailing and fabrication to ensure the geometry was correct to allow onsite erection. This issue was made harder with the design constraints set by the architect as all steels needed to stay within the timber cladding zones which were very tight to the steel lines.

Along with the link bridge GWS were contracted to supply and install a housing frame that enclosed the bridge from the new head office to the existing head office. This comprised of 15m long CHS columns with 18m long 914UB roof beams. On the outside of each of the CHS column machined support brackets were site welded in order to take the specialist glazing system. GWS undertook the engineering of these with the Glazing supplier as these had to be within 2mm in each direction in each location.

The contract comprised of 270t steelwork with some 1,300 members.