GEOMETRY OF CONCRETE FOLDED ROOF Author of the text: Jaroslav Hulin The irregular shape the folded roof is inspired by the Krkonoše Mountains. The loadbearing structure consists of folded concrete slab with its underside exposed in the interior. The slab is about 250 millimetres thick. All the above layers like waterproofing membrane, thermal insulation or the sedum layer are folded according to the concrete slab. The sedum layer is divided into triangular faces with metal gutter. The geometry of the roof was designed with regard to the construction process. All the fourteen faces were optimized to have a constant (but sometimes different from each other) thickness of all the layers which lead to substantial saving in the construction costs. Shape of the folded slab before cropping The faces meet in one vertex before offsetting and in multiple vertices after Offsetting an irregularly folded surface brings an immanent problem when a common vertex of multiple triangular faces splits apart into multiple vertices. If you randomly choose a point in space as the new common vertex of the offset surfaces, the triangular slabs will not have the constant thickness. One of the few ways how to achieve a continuously folded offset surface is to offset by a projection. The projection can be “perspective” (single focus) or parallel. The shape of the roof inspired by mountains and somehow spherical was more convenient to offset by a single focus projection. The position of the focus point was optimized in order to minimize the number of different thicknesses and to help the structural behaviour of the folded surface. In the end the fourteen surfaces consisted of only six different thicknesses. The optimization was carried out by proprietary written tools in a 3D modelling software. Common vertices of the faces offset into common vertices again. The slabs have different thicknesses. The selected focus point of the projection was placed about 30 metres below ground The final position of the focus point was optimized in many steps Every edge is emphasized by a metal gutter controlled by the same geometry as the folded concrete slab