Cultural and Congress Centre in Lucerne, Switzerland
Set in the city centre on the shores of Lake Lucerne, the various volumes of this complex are united by a striking roof structure. The roof extends out freely over the upper floors on the lake side with a cantilevered section 45 metres long on the diagonal. The top of the roof is structured by copper-clad steel girders. The broad roof projection visually reduces the size of the forecourt and serves to integrate this space into the building. Views of the lake can be enjoyed from the various terraced areas laid out at different levels beneath the cantilevered structure. The surface of the water is complemented by the smooth metal soffit of the roof, in which the surroundings are reflected. The cantilevered roof, supported without constraint by pot bearings on slender columns and individual walls, consists of a square lattice grid of welded steel girders up to 3.7 m deep and tapering to a point at the outer edge. The axes of the grid are at 5.4 ? 5.4 m centres. Additional stiffening is provided in the form of diagonal girders at the north-east corner. The copper roof covering is laid on wood boarding on timber beams. Deformation had to be kept to a minimum to ensure that the 7,000 m2 aluminium sandwich-panel soffit remains level. Spanned across the concert hall, therefore, are 32-metre-long trussed girders. The main beams over the museum tract consist of rolled steel sections up to 27 m long. The roof space is naturally ventilated. The edge of the roof can be heated to avoid the formation of icicles.