Firms building the London 2012 stadium were warned against complacency this week as they prepared for the project’s biggest technical challenge so far.
Construction of the key Olympic venue has just entered its second year on schedule, but Olympic Delivery Authority chairman John Armitt warned that erection of the £496M stadium’s cablenet roof was a major risk to the success of the project.
“Everybody in construction knows that a successful project is only ever a hair’s width away from a serious problem that can have serious consequences on your time, cost or quality,” said Armitt, writing exclusively for NCE (see ‘Expert Opinion’).
“The roof, which will cover 60% of spectators, carry lighting and cameras and play a vital role in the opening and closing ceremonies, is one of the major challenges ahead for the project as a whole. As with the rest of the building, a stadium roof has never been designed or built in this way before.”
Temporary crowd cover
Twelve of 28 steel sections of the roof’s compression truss have been lifted into place and are sitting temporarily on the stadium terrace’s steel rakers. Each of the steel roof sections, fabricated by Watson Steel, weighs 85t and is 15m high by 30m long.
“A stadium roof has never been designed or built in this way before.”
John Armitt, Olympic Delivery Authority
Over the next few weeks the remaining sections will be lifted into place and the truss will then move from its temporary support to independent steel support columns.
Once in place, strand jacking of the cablenet roof and membrane cover will begin to create a structure with a 28m overhang for the duration of the Olympics. It will provide cover to 60% of the stadium’s 80,000 capacity crowd in games mode, before being dismantled along with the steel raker terraces after the games to leave a 25,000-seater roofless stadium.
At the same time as preparing for the roof erection Team Stadium − the consortium building the structure that includes contractor Sir Robert McAlpine, structural engineer Buro Happold and architect HOK − has already begun internal fit-out of over 700 internal rooms.
In the first year of construction work on the venue, more than 4,500 reinforced concrete columns have been installed into the ground, all 112 steel rakers have been fixed to act as the terracing supports to hold the 55,000 seats in the upper tiers and 5,200 of 12,000 pre-cast concrete terracing units by Tarmac for the seating have been put in place.
The first permanent foot bridge to the stadium, which is located on an island in the south of the Olympic Park in Stratford, has been lifted into place and work on the abutments of the other four bridges are complete.