The interior of the church expresses a contemporary interpretation of the liturgy with a centrally positioned altar. The conical building envelope clad on the outside with wooden shingles encloses the church’s interior and is both a roof and a wall. The rooflight and flat side window, as planar interface surfaces, differentiate themselves from the geometry of the building’s basic form and bring the 20 m high space to life with an exciting combination of light entering vertically and horizontally. After the dedication of the church, scheduled for March 2018, the community will have access to a sacred space with a special aura.
Two different structures
Although the church and the chapel are both inclined truncated cones, their load-bearing structures are remarkably different. The main structural element of the chapel comprises glued laminated timber (GLT) beams running in the principal direction of fall of the cone sides and restrained by a flexurally stiff ring at the crown of the roof. The system is stiffened by wood-based board external cladding. At the large window opening, the beams are not supported on the ring foundation, but are connected to a parabolic, block-glued GLT arch. The arch’s horizontal deflection was calculated using a 3D analysis to design the components and their connections. The result was that GLT rings, flexibly stiff to resist transport loads, were attached at the beam third points to stabilise the main structure of the chapel.
Church main load-bearing structure
The church is elliptical in plan with a diameter of approximately 34.5 m and 21.6 m high. The structure is terminated at its highest point with an inclined rooflight constructed from a slender steel grillage. The dissolved, exposed shell construction is composed of GLT struts, which form triangles and therefore fulfil stiffening and load-bearing roles. The corners of the triangles meet at nodes at the intersections of the fall lines of the cone with the differently inclined intersection planes. Thus the structure has approximately 350 of these nodes, which are normally a mirrored arrangement of two adjacent triangles. The elliptical rings within each intersection plane are one-piece, curved GLT beams with flexurally stiff joints. The diagonally running struts were initially idealised as members of a pin-jointed truss in the early 3D calculation model. However, they were predominantly loaded in compression and therefore later modelled as pure compression members that would fail under tension, in order to optimise the connections. The diagonals are kept in place by steel tie rods spanning between two adjacent rings at regular intervals and following the principal direction of fall lines.
Node connection design
As a result, the connections at the nodes could be designed to transfer the normal forces in the diagonals by contact pressure only. At the standard nodes, steel wedges were welded onto the steel baseplates on the top and bottom faces of the rings. The ends of the diagonals, on the other hand, were shaped to the negative form of the steel connection surface by CNC machines. Fabrication drawings were produced by the timber construction company based on a 3D computer model containing not only all the timber components, but also all the steel parts and fastening materials, to ensure that the required extremely high degree of accuracy of fit was achieved. Steel cylinders through the rings connect the baseplates and transfer the forces from the upper to the lower diagonals. For aesthetics and fire protection – an R30 rating applied to the load-bearing structure – all the connection fittings were concealed.
Special solutions
The timber construction company submitted a special proposal for the upper, more lightly loaded nodes. This enabled 245 of the “steel” nodes to be replaced by prefabricated pieces of beech laminated veneered lumber (LVL). The roof elements were also prefabricated to minimise the possible effects of the weather.
