The arch is not an architectural folly - it plays a key structural role, holding up 60% of the roof. On the north stand, towards which the arch will permanently lean, it picks up a perimeter truss at the rear and a truss at the front.
This holds up four trusses spanning the pitch from the south stand, needed to support the moving roof when the stands have to be covered over. Loads from the front truss are transferred via cables to the arch. Total weight to be supported by the arch will be 7,000t.
Deflection of 600mm is expected when the arch is fully loaded.
Trusses spanning the pitch have been designed to minimise shadow effects on the pitch such as the 1986 World Cup 'spider' shadows. The moveable roof will not enclose the whole stadium, just the fans - the players deserve to get wet.