Author – Andrew Watts

In his book ‘Modern Construction Case Studies’, Andrew Watts of Newtecnic describes the design of the structural envelope for Istanbul City Museum:

The structural envelope is composed of a continuous framed wall which is designed to accommodate are sharp folds that define both the internal and external architectural surface, which closely follows the same geometry. The structural concept for the framed wall follows the direction of the frame elements in each facet to form we folded surface, as well as the structural depth of the wall required to achieve sufficient stiffness. The structural depth of the cold pressed steel members is balanced with the spacing between them as well as the ability of the wall framing to incorporate connections with the exterior aluminum rain-screen cladding.

Two layers of the outer wall are used: a framed backing wall and an outer rain-screen cladding which is supported on rails. The external open-joint-ed cladding is set out along diagonal lines and supported on aluminum rails, which are fixed to the framed wall in order to minimize the lumber of penetrations of both thermal and waterproofing envelope. The framed wall construction provides the required global stiffness to support the cladding. Localised forces, which result from the use of thin pressed sections, are accommodated at folds in the facade.

The continuous framed wall envelope is top-hung from the slab edge of the highest floor and is restrained by slab edges on floors beneath, as well as at the interface with the ground floor-grazing. At these points, the restraint is only for out-of-plane movement and allows the hanging folded facade to move freely.

The framed wall incorporates movement joints only at corner locations, in order to allow unrestrained thermal movements to be accommodated for each side of the building. Framing members run in the two perpendicular directions within the plane of each facet, which introduces diaphragm action and provides global stability to the envelope. The setting out and installation of the framed wall is performed through semi-prefabricated modules, where thermal insulation, membrane, and interior finishes are site-assembled. The rails are fixed directly to the framed wall trough adjustable thermally broken brackets in order to support aluminum panels along the long edge.