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Body building Dome

MILLENNIUM DOME; A modern version of the Statue of Liberty is taking shape in Greenwich. Dave Parker reports from the Millennium Dome.

Towering over every other structure inside the Millennium Dome, the 27m high Body Zone represented a unique challenge for structural engineer and contractor alike. Zone architect Branson Coates partner Doug Coates says: 'It's basically a nine-storey high body-shaped building, half male, half female.

'This is a long way from the original concept, which was little more than a simple statue with nothing inside it.'

Once the decision was made to turn the Body into an exhibition venue in its own right, it soon became obvious that more habitable space was needed than an erect figure could provide. 'Laying it down created the space - and made things like wheelchair access much simpler,' Branson reports. 'The final design was worked out by hand on a small clay model, which was then scanned by laser and the results fed into the computer.'

The task of turning the concept into a structure which would be able to support not only itself but the people and equipment inside fell to Buro Happold. Project engineer Andrew Best says that two main structural options were considered.

'We first looked at a grid shell design, where the skin would take all the loads. The problems were that every structural member would be different, every structural member would be curved, and the whole thing wouldn't be stable until the last member was in place.'

Another consideration was the short timescale of the project. Buro Happold finally decided to go for a steel endoskeleton supporting an unstressed skin, with the main structure made up almost entirely of straight elements.

Branson says that at this point there had been no final decision on what the skin would be. 'It could even have been papier mache as there is no need for water resistance inside the Dome.'

Although the 120 figure forming hoops would catch the eye once construction began, these have only the secondary structural function of supporting the skin. The main load bearing structure comprises a main platform - which will take the visitor loads - a sloping tower reaching up into the head area, and two horizontal 'booms' - one at the shoulder level and one to support the heads.

A mixture of standard steel beams and tubes was used for this part of the structure, all straight. The cone-shaped male foot, which cantilevers 15m out from the main Body, uses structural hoops bent to skin profile welded to the primary structure to form a Vierendeel truss.

'Otherwise the tubular skin supports were fairly light sections, which were easy and cheap to bend,' says Best.

'The only problem was the flexibility of the steel structure. If we chose a relatively stiff skin, live load stresses would be transferred into the skin - which would have to be designed to take them.'

The biggest problem in the choice of skin material was accurately reproducing the curves and undulations of the clay model on the full size figure. Structures like the Body are rare, to say the least, although there is a tradition of novelty restaurants in the shape of lobsters or chickens in countries such as the US.

Recently, in Singapore, a 35m high figure of a 'Merlion' was successfully skinned with glass fibre reinforced cement. When the Body team contacted Glenn Industries, the Australian spraying specialist concerned, they found the answer to their reproducibility problem. Glenn's system is based on the use of modern surveying technology linked to the CAD model of the original figurine. Lengths of 20mm rebar are welded to the hoops every 600mm. These project beyond the limits of the skin until the exact length is set bya sophisticated mobile workstation which orients itself from reference points set up around the periphery of the zone.

The surplus bar is clipped off and a short length of 10mm bar welded on at right angles. A 300mm grid of 10mm bars is then woven around these support bars, and covered by lightweight expanded metal sheeting.

'The setting out includes allowance for deflections, but the final alignment of the expanded metal is down to two sculptors working for Glenn,' Branson explains. 'Overall, the standard of workmanship on the skin has been superb.'

More than Australian know-how has gone into the 15mm of GRC that forms the 4,200m2 of the Body's skin. Glenn has also imported the pure silica sand needed from Australia as well.

'Grading curve, particle shape and moisture content are critical,' explains Glenn project director Glyn Sennar. 'Finding an identical sand here would be very difficult and trial mixes would take too much time. It's easier to stick with the sand we know.'

The 'very low water/cement ratio' mix contains 3.5% by weight of glass fibres, which are chopped into 38mm lengths at the spray nozzle. Glenn approached specialist Putzmeister to supply the necessary spraying stations, which had to be positioned on and moved around the surrounding scaffolding birdcage erected by Kwikform. Putzmeister's answer was to adapt its portable S5 EV/CMP station, normally used by the steel industry to reline tundishes.

Senner says that application rates of up to 200m2 a day have been achieved. Final finish is achieved 'by mitten' - two men wearing mittens carefully smooth the surface down. This got the tabloids excited. When the secondary sexual characteristics on the female half of the figure were being smoothed, several sent photographers. Unfortunately for them, the density of the scaffolding around the torso spoilt the pictures.

As the GRC cured, specialist tiling subcontractors followed with the finishing touch. Specially manufactured, overlapping 'lenticular' plastic tiles, which appear either pink or gold depending on the angle of view, are now being glued on.

Best says Glenn is slightly ahead of schedule 'and has done a fantastic job'. Even when the other 13 zones are complete none is likely to be as immediately dominating as the Body. With less than three months to go, the Body is on course to be the star attraction of the Millennium Experience.

Inside the Dome, work on the 17 themed zones is in full swing. Each zone is a construction site in itself, with individual teams of contractors, consultants and architects beavering away under the vast Dome canopy.

Faith

Theme: religion

Status: 17m high arches which will support six canopies enclosing the zone substantially complete.

Structural engineer: Techniker

Sponsor: Religious organisations and Laing family

Home Planet

Theme: Travel and discovery

Status: Blue, lozenge shaped advanced composites structure nearing completion.

Structural engineer: Buro Happold

Sponsor: British Airways, BAA

Journey

Theme: Journeys

Status: Erection of 25m high angled fin structures for this zone has just begun.

Structural engineer: Buro Happold

Sponsor: Ford

Learning

Theme: Education

Status: 11m high structural steel frames supporting rotating tryptich boards complete.

Structural engineer: Buro Happold

Sponsor: Tesco

Living Island

Theme: Environment

Status: Steelwork in place

Structural engineer: Buro Happold

Sponsor: To be announced

Mind

Theme: The human mind

Status: Steel frame for suspended structures under construction. When this is finished it will be clad with glass reinforced plastic panels.

Structural engineer: Ove Arup

Sponsor: British Aerospace, GEC

Money

Theme: Money's impact on the world

Status: Ground floor steel superstructure in place

Structural engineer: Atelier 1

Sponsor: City of London Corporation, financial institutions, De Beers, Royal Mint

Play

Status: Steel superstructure under construction

Structural engineer: Buro Happold

Sponsor: To be announced

Theme: Future of recreation

Rest

Theme: Relaxation and contemplation

Status: Ground works complete. Superstructure work to start soon.

Structural engineer: Buro Happold

Sponsor: To be announced

Self Portrait

Theme: Celebrating Britain

Status: Steel superstructure complete

Structural engineer: Buro Happold

Sponsor: Marks & Spencer

Shared Ground

Theme: Local communities

Status: Recycled cardboard columns 14m high, under construction

Structural engineer: Buro Happold

Sponsor: Camelot

Talk

Theme: Communications

Status: Steel frame complete

Structural engineer: Buro Happold

Sponsor: BT

Work

Theme: Future of work

Status: Steel frame

Structural engineer: Buro Happold

Sponsor: Manpower

Our Town stage

Theme: Town life

Status: Groundworks complete ahead of construction of tented structure

Structural engineer: Buro Happold

Sponsor: McDonald's

Skyscape

Status: 122m long, 56m wide and 21m high superstructure almost complete.

Structural engineer: Edwin Shirley Staging

Sponsor: Sky

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