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Wembley Arch
Introduction The "new" Wembley Stadium was built between 2003 and 2007. The stadium was jointly designed by Populous and Foster + Partners. Engineering by Mott MacDonald. The stadium was built by Brookfield Multiplex. The stadium cost nearly eight hundred million pounds to build and was jointly funded by the English FA, London Development Agency and the UK Department for Culture Media and Sport. The seating capacity for football matches is ninety thousand. With every seat covered by a sliding roof, no other stadium has more seats undercover and protected from the elements. Wembley also holds the record for the most toilets in a sports stadium, the exact number is two thousand six hundred and eighteen. The original stadium's signature was it's twin towers. Prior to breaking ground in 2003, there was a national campaign to retain the twin towers or rebuild some replicas for the "new" Wembley. Neither campaign was successful, instead of the twin towers the new iconic feature for Wembley stadium would be a circular arch. The designers, Foster and Partners, had planned a four-mast design before the arch, but felt the 'circus tent' look lacked a unique appeal. The arch design used a third less steel than the mast design, and did not add further costs to the project. (mast design pictured below, click to enlarge). The Wembley arch is currently (2009) the world's longest single roof structure. The arch is illuminated at night, and is dramatically visible from across London. This is achieved by two hundred and fifty eight floodlights (halide) which have been placed within the arch. Structure The exact statistics of the arch are as follows, Span - 315 metres Structure - Mott Stadium Consortium The arch's function is not solely cosmetic, it also helps support the
complete weight of the north roof and sixty percentage of south roof's
weight. Mineral Star, a small roofing company based in Northamphamshire
were tasked with completing the roof of Wembley Stadium. The structure
of the arch was fabricated onsite, and covered a ten month period. Sheds
were erected where the Wembley pitch is, and used to construct thirteen
steel modules, these were eventually connected to make up the arch. The
company tasked with the work was Cleveland Bridge, who used British steel.
One of the milestones of building the "new" Wembley Stadium was in the positioning the arch. Nobody was exactly certain whether the concept would work, so a certain amount of anticipation and nervousness was generated before the final positioning was completed in 2005. The initial lifting of the arch was scheduled for March 2004, but was delayed, due to minor defects being discovered in the steel Therefore, the arch was finally lifted into position in June of 2004. The process was controlled by computers, with the arch gradually winched to thirty, sixty five, one hundred and finally one hundred and twelve degrees to vertical. The process was far from simple, and involved cranes and massive computer controlled jacks (from Fagioli PSC) placed on struts. The arch incorporated temporary pin joints, which allowed it to rotate while being erected. The pins were welded in place after the arch was lifted. It was only until late 2005 that the whole procedure was complete. It
took a year for the load tonnage to be transferred from five temporary
retraining cables. During this time new backstay cables needed to be connected
to a perimeter truss, a permanent cable net and eye brow catenary cable
were put in place, and the arch was finally rotated to take the roof load.
Why did it takes so long?, it appears that the positioning of the arch
was only conducted during the weekends, which allowed construction of
the stadium to continue during weekdays. The structure of the arch is a latticework. A lattice is described as "crossed strips of metal or wood, arranged in a pattern to form a structures". The key advantage of latticework is the low wind load it incurs. With the Wembley arch being so high and long, the danger of high winds damaging the structure was a key concern. The Wembley arch latticework is composed of forty one steel rings. As the above image displays, you can see three of these rings highlighted. The rings are connected through tube chords which spiral around the structure. As the above image displays, the base of the arch tapers to 1.5 metres in diameter as it enters the ground. The base is supported by hinges, which are in turn supported by a concrete base. The concrete base is founded upon piles which reach thirty five metres into the ground. You may faintly beable to view the backstay and forestay cables attached to the arch. These are the cables which connect to the stadium's roof structure. They are placed in a diagonal system which spreads the load and helps avoid bending and buckling. A catenary cable was a primary component in fixing the position and load sharing of the arch. The arch is positioned one hundred and twelve degrees to vertical. One reason why the arch is positioned at an angle, is so that it will not cast a shadow onto the pitch during daylight matches. The arch nearly breaks the height allowed for buildings in it's area, the reason is due to low flying aircraft's, therefore, the arch has an aircraft safety light at it's top. Reception The first time fans were allowed to browse the new stadium was on the 18th of March, 2007. An open day was provided to local residents and England supporters, numbering 60,000. No official figure of how many attended was announced. One fan noted the excellent view from any seat. No comments on the arch were printed in major publications during the community day. The arch had been on view for a few years before the stadium's community day. The first time the arch was lit was to mark England’s victory over Croatia, and progression to the Euro 2004 quarter final versus Portugal. The arch will be lit for every England night game played at Wembley. The arch has been likened to a giant halo or beacon. On a clear night, when the arch is lit, it can be seen for thirteen miles across greater London. Whether the arch will become a much loved iconic like the twin towers is still up for debate. But few people will doubt the dramatic effect it lends to the stadium and local area.
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