The underlying ground conditions on the site suggested that traditional spread footings would be suitable. Given the concentration of loads under isolated columns, reinforced-concrete pad footings were used.
The main superstructure elements consist of precast, prestressed concrete slabs, supported on precast concrete beams and columns.
The ground-floor slab at datum level consists of a ground-bearing, mesh-fabric reinforced concrete slab built directly off the ground and supported on hard core. Throughout the ground floor, precast concrete columns based on a 10 x 10m grid were provided to support the first-floor slab at level +5.5m.
The first-floor slab, level +5.5m, consists of 450mm-thick prestressed concrete double-T slab units spanning 10m between primary floor beams. These primary floor beams again are single inverted T-sections, having an overall depth of 450mm, and span between columns.
Movement joints are provided within the structure at intervals of about 50m to minimise the effects of movement caused by shrinkage, temperature variations, creep and settlement.
The structure is framed on both sides of the joints by means of nibs or corbels provided off the walls and columns, with a sliding bearing to support the slab or beam to one side. The area of first-floor slab, which cuts across at an angle in front of the main entrance, has a clear span in excess of 45m. The floor-slab construction in this area consists of a series of trapezoidal precast concrete segments, which vary in depth from 3.5m to 4.5m. These precast-concrete segments, each 2.4m in length, were constructed initially on falsework and coupled together using hightensile prestressing strands that were posttensioned and grouted to form a continuous beam. Five raking thin columns cluster together to form an A-frame support at one end of the span, while a simple vertical wall incorporated into the adjacent car-plant building provides support at the other end.
In-situ reinforced-concrete walls surrounding the stair and lift cores act as main bracing elements to assist lateral stability loadings from the structures at each level. These walls also provide vertical support to the first floor and roof-slab elements.
The roof structure generally consists of precast double-T units supported on precast beams based on a 10 x 10m grid and supported on columns. However, in certain areas a lightweight roof consisting of a steel space frame structure is provided. This lightweight roof consists of elongated hexagonal cells constructed from hollow-section steelwork.
Isolated columns continuing up from the firstfloor slab provide vertical support to the roof on a 20 x 30m grid spacing.