Quality in Construction Award, Building of the Year

Bullring Spiral Cafe, Birmingham | Marks Barfield Architects

The form of the cafe is derived from sweeping a Fibonacci spiral to create a shell-like canopy. The structure is contained between the inner and outer curved surfaces of the canopy; it both supports the cantilevering roof and provides accurate formwork from which the rest of the construction can take its shape. The eight structural ribs are arranged radially in plan and each tilts up relative to its neighbour to create the shell-like form. A series of CHSs are set diagonally between the ribs; together they act as a cantilevering shell structure. The ribs are supported at points under the roof of the servery and at the roof level of the rear annexe. Further stiffness is generated by the CHS braces between the ribs, which together act as a cantilevered truss supported at the outer tips of the first three ribs. To simplify fabrication as much as possible, the structure was made from mild-steel plate ribs cut on a computercontrolled plasma cutting machine. This meant that the form of the building could be manufactured easily, with a number of curved ribs defining its shape. Obviously three dimensional modelling was critical to the design. A product design program was used to develop a parametric three dimensional model. The program was used to model all structural elements and many architectural elements, such as cladding profiles and glazing interfaces. As part of the design process, the architect and the structural engineer worked together on the same three dimensional model, taking sections and profiles from it to develop further details that were not modelled three dimensionally. 

Source: Steel Construction