Stressed Skin Membrane. The SSM-System varies depending on material type. An incredibly light single skin system uses a single layer of ETFE with biaxial tension applied by low force perimeter tensioning. The perimeters and panel intermediates are realized from aluminum extrusions which are anodized, or powder coated. The intermediates often use internal guttering. Additional transverse load transfer can be provided by thin prestressed stainless-steel cables in ETFE pockets on the lower side of the surface. Cable spacing is determined from environmental loads and the drainage needs very careful planning as the ultra-light system is flexible and deflects easily. Typically, the cables are one directional and spaced at around 2’ (600mm). The weight is below 1 psf (0.05 kpa) making it arguably the lightest enclosure system on the market. Where smaller pre-made aluminum framed panels are feasible, cables are eliminated and the system is unitized. ETFE in a single skin system has a very nominal thermal performance and shading is best accommodated by using colored, solid or translucent material.
The SSM-System for more robust designs using PVC and PTFE materials require higher prestress which is applied using heavier edge profiles. Typically, the materials are stretched over spaceframe grids or stiff steelwork to limit membrane spans so that cables are not required, and tension forces are held within the steelwork. Once stressed, clamping bars are applied as required to prevent uplift. PVC and PTFE materials vary in opacity, but are not transparent.
Applications include canopies, small span ribbon skylights, screens, walkway covers, shade covers and green areas.