HQ right on cue
A timely return to form for the England Rugby team is being echoed by the construction of a new South Stand at England’s home. Mark Hansford reports from Twickenham.
On the pitch, English rugby may owe its return to rude health to one man – the heroic Jonny Wilkinson – but at its spiritual home, Twickenham, it is a very different story. The fact that a full house of 82,000 was able to witness the great man’s return in the opening two matches of the Six Nations, not to mention the four Wilkinson-free autumn internationals, owes much to the team efforts of Carillion, the contractor rebuilding the stadium’s South Stand.
Completion of the new stand is the final piece of the Twickenham jigsaw. The North, East and West stands were rebuilt during the 1990s and the new 40m tall South Stand will make the whole arena a three-tiered bowl, the largest dedicated rugby stadium in the world.
But smashing down the 10,000 seat, 26 year old post-tensioned concrete South Stand, with its cable stayed barrel vault roof, and replacing it with an £80M, 17,000 seat stand made of, precast concrete, insitu concrete and structural steel was never going to be easy.
Work is taking place while the stadium is in operation and contractor Carillion must enable it to operate at a minimum capacity of 65,000. And this minimum is being increased incrementally as the new stand develops in line with demands from client the Rugby Football Union (RFU).
The new structure also incorporates a four-star hotel, conference centre, health and fitness club and a 400 seat performing arts centre.
Carillion took over the job as part of the portfolio of projects it acquired when it bought Mowlem in early 2006. Mowlem won the fixed-price contract in early 2005 and arrived on site on 18 July 2005, eight days after Controlled Demolition had blown down the original stand. Time was of the essence, as the RFU wanted the 7,600 seat lower tier available for the opening Six Nations match with Wales on 4 February 2006. “Unlike many other buildings, if this one was not complete it would be noticed – international rugby matches don’t get rescheduled because the contractor wasn’t ready. It had to be there,” says Carillion project director David Goward.
Mowlem had rebuilt the other three stands in the 1990s with insitu concrete, but this stand, with its wrap-around “commercial building” was a different prospect.
“The commercial building has made it different in a number of ways,” says Goward, himself a veteran of Mowlem’s previous Twickenham work.
“For a start we couldn’t have tower cranes sat back – they had to come up through the building – and on the back of the other stands there are staircases. We have got spiral ramps (one on each corner). They are not unusual, but they do take up a lot of space.”
Each spiral is in a 25m diameter insitu C35 concrete drum. “They work as shear cores for the predominantly steel-framed commercial building,” says Goward. The commercial building is designed to work independently of the stand itself, with a lift core between the two drums providing a third shear core.
The other three stands were little more than tin shacks before they were rebuilt. “It was going to take longer to clear and we were going to have piling to do, the obvious way to save time was to use precast concrete for the lower tier,” says Goward. This was designed, supplied and installed by ABC Structures (see box); the tier was ready for the Wales game. So far so good.
The next milestone was to have the second and third tiers – along with the roof – ready for the autumn internationals, starting on 10 November against Australia. “That was a big target for us,” says Goward.
The middle and upper tiers are steel framed with the same precast concrete terracing, the roof is a steel truss infilled with purlins and a translucent cladding. They are cantilevered off an insitu concrete Vierendeel sway frame.
Named after Belgian engineer Arthur Vierendeel, this truss has rigid upper and lower beams, connected by vertical beams. At Twickenham the vertical beams are a massive 1,500mm by 750mm at 7m centres. The joints are also rigid. In this statically indeterminate truss, all members are subject to bending moments. By eliminating diagonal members, the creation of rectangular openings for windows and doors is simplified since this truss can reduce or eliminate the need for compensating shear walls.
Unfortunately construction did not go smoothly. “There had been some problems,” says Goward. “The west drum was to be built on the site of an existing electricity substation that we were going to rebuild and incorporate into the drum’s core.
“We built the new substation, but there was quite a long delay in getting disconnected and reconnected. That delay meant we couldn’t start piling or anything,” explains Goward.
The delayed construction of the concrete sway frame in turn delayed Cleveland Bridge, which was contracted to erect the steel frame and precast concrete terracing for the middle and upper tiers. “We needed the three cranes being used to erect the concrete frame gone, so we could erect Cleveland’s larger cranes,” says Goward. “This was going to delay them.”
Carillion decided to ask the RFU if it could install two additional tower cranes so Cleveland Bridge could get started on the middle and upper tiers while the concreting work was finished off.
“Running with five tower cranes was difficult, but we managed,” he says, ruefully adding that the RFU was about to crank the pressure up further by springing a surprise rugby fixture on the contractor.
“We had the date of 10 November originally, but then the client asked if he could arrange another match. We said ‘when?’; he said ‘5 November’. We said ‘okay’, but then the RFU started to bill it as the grand opening of the stand, against New Zealand, with fireworks!
“We didn’t want to become the next Wembley, so we put in a huge effort,” says Goward. And the team made it, with the last section of precast concrete terracing going in on the Monday before the game. England were hammered, but Goward’s team were still jubilant.
“We all got a lot of pleasure from meeting the deadline. The feeling is like the Oxford and Cambridge boat race. Both teams have rowed the course, but one team is elated and the other flat. We were elated.”
That said, Goward knows there is still no room for complacency, with a 41m cantilever roof still to go on and a hotel to complete. The steelwork should be up and the cranes down by the end of April. The roof cladding will be installed by the end of May. “We are pushing on with the roof and you will see a lot of difference by the time of the France game [on 11 March],” says Goward. If England triumph in Dublin this weekend, that will be a Grand Slam decider.
A revitalised Twickenham eagerly awaits.