Ove Arup & Partners
The buildings were always conceived as long buildings three storeys high and about 15 metres wide. The design generators were low energy, a curved plan form, simple repetitive cladding and the need for flexible partition arrangements. The structure also had to be low-cost and imply a small storey height.
The chosen option for the floors was a 275mm-thick in-situ concrete flat slab supported by columns set into the perimeter wall, and an internal row of central columns at approximately 6 meter centres. The in-situ concrete slab was constructed in Grade 35 concrete, cast on standard sheets of plywood shuttering. The soffit has been painted. The floor finish is carpet on screed.
The columns in the wall are rectangular, 200mm thick and of variable length. The columns at mid span are circular and 350mm in diameter.
Transverse stability is provided by shear walls some 50m apart at the end of each block. Longtitudinal stability is provided by the columns in the perimeter wall frame acting as a moment frame with those in the centre of each building being longer and therefore stiffer than those at the ends. This arrangement was chosen because of the comparatively long distance between expansion joints.
The roof structure is structural steelwork with 356mm or 406mm deep ubs clear spanning across each block.
The ground slabs were all cast on the ground. Where they were cast on exposed original Keuper Marl clay they have been designed as ground-bearing and are 175mm thick. Elsewhere they are designed to span and are 275mm thick.
The foundations are simple strip-and-pad footings formed on the underlying Keuper Marl clay with a bearing capacity of 250kN/m2.
The external wall of the building is constructed of render on insulation on a secondary structural sub-frame which spans between the slabs and columns in each panel of the elevation.