The roof and the giant dish are supported on huge pylons, with services and circulation, such as escalators and stairways, accommodated in the cruciform-shaped zone, defined by the four raked pylon structures.
The design is based on a series of separate and complementary structural systems which allows a variety of activities and user requirements to take place on different levels inside the building. The dish supports the cupola/dome, creating an open and flexible space. Its columns travel down to ground level within the four atria; bridges, lifts, escalators and walkways either pass through these columns or on either side of them. This also allows for an open, column-free space at level 4 and removes the need for any structural members to pass through the cinema spaces below at levels 2 and 3. These cinema spaces are formed by large steel cantilevered boxes that effectively constitute a separate, self-contained structural system within the building and rest on a concrete base at level 2.
From level 2 downwards, a more conventional concrete column and floor slab construction has been used for the retail areas. The design of the column layout has provided the spaces required by the client for different retail zones; these columns continue into the four levels of car park below, creating a logical layout for vehicle access and parking.
Additional, separate structural systems support the existing façade of the historic bullring (providing maintenance, fire escape, services and access gantries) and the adjacent Eforum, which connects with the retail at ground level and also with the car park and basement ramps. Between the bullring façade and the Eforum is a services spine and large goods lifts, with other services for the bullring complex placed on the roof of the Eforum.
The 96-metre diameter roof dome is finished with a beige plastic coating. This complements the adjacent roofscape and also helps to reduce glare from reflected sunlight. The relatively shallow dome rises only ten metres from its perimeter to the centre. While this geometry is structurally challenging, with its susceptibility to buckling and large deflections, the dimensions were non-negotiable, having to keep within an envelope agreed during the initial planning consent. The maximum crown height was fixed to reduce the visual impact of the roof from a nearby historical fountain.
The dome complements the adjacent roofscape and also helps to reduce glare from reflected sunlight. Natural daylight is utilised throughout with glass facades to the four entrance spaces surmounted by corresponding glazed zones in the dish roof above to illuminate the central space. High performance thermo-solar energy collector panels are used to harvest solar energy to provide hot water for the building.
Large external landscaped areas surrounding the bullring provide high-quality public open space that also serves to connect the building to the metro station and the adjacent park. The roof-top piazza and the viewing platforms provide additional public space with spectacular views over the city.
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