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Keeping it simple

Stadiums - Arsenal football club's stunning new stadium has nished early and under budget. Ruby Kitching meets its construction manager.

Accompanying the cheers at July's Dennis Bergkamp testimonial match was a more restrained celebration from the team which built Arsenal's new Emirates Stadium.

Safe completion of the match marked the end of a series of tests held to ensure the stadium is signed off by the police and re brigade in time for the start of the football season last month.

Contractor Sir Robert McAlpine's construction manager Andrew Veness was there to raise a glass to ve years of working with client Arsenal Football Club, engineer Buro Happold, project manager AYH and architect HOK.

So how did he make sure the project did not enter extra time?

'By keeping it simple, ' is the succinct reply from the 45 year old chartered civil engineer. He adds that necessity drove the need for simplicity when funding for the project was looking shaky in 2003.

Wembley had just got its funding, and the banks were not keen on spending money on another stadium. So some funding for Emirates was cut.

Veness explains that each stage of the construction process was analysed in consultation with subcontractors and suppliers to minimise risk and secure programme and costings to get it built.

'The most impressive thing about the stadium is its sheer simplicity, ' he says.

'There isn't a single wowfactor element. It doesn't get much more interesting than the inclined curtain walling near the entrance, ' he says modestly.

The new stadium is located on a triangular 7ha browneld site in North London, hemmed in on two sides by railway lines.

McAlpine's brief was to demolish existing buildings, clean up the ground, install 1,400 piles, erect two bridges over the railway, and build a new waste facility for Islington Borough Council.

Oh, and build a world class 60,000 seat stadium, all for ú390M ($741M). Simple.

The project was procured as a two-stage, lump sum, guaranteed maximum price, design and build contract with full t out and building services.

Or more plainly, McAlpine would take construction risk but have the opportunity to firm up the design before agreeing to a price.

The first stage involved submitting brief method statements, a construction programme and initial cost estimates.

Veness joined the project when McAlpine was asked to continue to the second stage of the contract, where risks and costs were defined in more detail. The McAlpine site set up was almost self sufficient; the planning programming, procurement, design and costing was all site based.

The stadium roof posed a significant design risk due to the long lead-in time for fabricating, transporting and erecting components.

And working with subcontractor Severfield Reeve/ Watson Steel before signing the second stage contract led to the method of erection being completely revised to make it easier to build (see box).

Other mplifications to stadium construction included stripping out thinner posttensioned concrete slabs for the internal floors. These could have created more space to accommodate services, but using traditional reinforced concrete made it easier to detail box-outs when more information came in.

'We've had to drill hundreds and hundreds of holes to accommodate services ? we didn't try and cast them before because this would have just held back concrete pours, ' says Veness.

Using precast concrete terracing instead of casting it insitu and using traditional jumpform methods instead of continuous slipforming for the internal cores were also adopted to keep things 'straightforward'.

The project was priced using open book principles.

This is not to say that there was less pressure on McAlpine to keep costs down. Where Veness' team came in under the guaranteed maximum price, McAlpine stood to share half the savings.And if the stadium went over budget, it would take the sting.

To the project's advantage, the design team was novated to McAlpine from the client. This meant no time was lost bringing a new team up to speed when the second stage of the contract was underway.

However, no project which has been going for nearly five years is completed without a few blips.

The biggest came in April 2003 when planning and land acquisition delays held up stadium construction, pushing the anticipated completion date back from 2005 to 2006.

This coincided with the project's funding stalling, plunging the scheme into limbo.

But instead of sitting back and waiting for the project to sort itself out, McAlpine diligently worked away on parts of the site it could.

By February 2004, the project was back in action, and this time with the client adding an extra ú35M ($66.5M) to spend on upgrading catering, toilet and hospitality facilities.

'But this had the knock on effect of increasing the power requirement from 7MW to 14MW, ' says Veness.

This meant cabling and ductwork took up more space, requiring larger service voids in more locations.

The client took on the design risk of this extra work and made sure that queries were dealt with quickly as they arose.

'The client would tell us what he could afford and we'd try and work within that budget, realising that any savings would benefit us in the long run.' 'The client knew that if he changed the scope too much, it would come back and hurt later.' And the success of the project certainly speaks for itself. Key deadlines, such as the major footbridge slides across neighbouring railway lines and roof truss de-jacking, were met and the stadium was finished two and a half weeks early.

The stadium was also completed under budget, in stark contrast to Wembley, that other north London stadium.

Roof steelwork To save vital time the roof construction method was changed so that tubular steel trusses could be bolted together 'in the air' rather than being welded.

Primary trusses supporting the roof run north-south, while secondary trusses run east-west. All are connected back to a perimeter roof truss via tertiary trusses.

The two 204m long primary roof trusses were built side by side in two halves using the pitch area as an assembly yard. This took place while work was underway on the surrounding stadium bowl.

Originally the whole primary truss was to be assembled on the floor in one piece, but the ends would have encroached on parts of the construction area for the stadium bowl. This would have meant that some parts of the bowl would have had to be delayed until the trusses had been lifted.

Each primary half-truss was lifted by crawler cranes onto a temporary platform at one end and concrete core at the other.

Services were installed on the trusses prior to lifting, to save time.

To save vital time the roof construction method was changed so that tubular steel trusses could be bolted together 'in the air' rather than bein g welded .

Primary trusses supporting the roof run north-south, while secondary trusses run east-west. All are connected back to a perimeter roof truss viatertiary trusses.

The two 204m long primary roof trusses were built side by side in two halves using the pitch area as an assem bly yard. This took place while work was underway on the surrounding stadium bowl .

Originally the whole primary truss was to be assembled on the floor in one piece, but the ends would have encroached on parts of the construction area for the stadium bowl. This would have meant that some parts of the bowl would have had to be delayed until the trusses had been lifted .

Each primary half-truss was lifted by crawler cranes onto a temporary platform at one end and concrete core at the other.

Services were installed on the trusses prior to lifting, to save time.

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