bright zinc-plated steel the SAVARIND concept components manifest specifies Grade 8.8 bright zinc plated (BZP) steel threaded rods, M16 Form G washers, wing nuts and hex nuts. Together they form a demountable structural frame, chosen for its mechanical performance, its resistance to wear in use and the protection it gives to the timber. Grade 8.8 carbon steel has a nominal yield strength of 640 newtons per square millimetre, giving a wide margin between working loads and permanent deformation (Bickford, 1995, pp. 135–142). When tightened to normal clamping forces, the rod remains within its elastic range, so the joint stays rigid. The timber itself will still creep under sustained load and move with seasonal changes in moisture, so joints may need occasional re-tightening, which the system is designed to allow. Grade 8.8 steel is quenched and tempered, giving it a harder, more wear resistant thread surface than austenitic stainless steel, which is comparatively soft and more prone to thread deformation under repeated loading (Davis, 1994, pp. 113–116). Stainless steel fasteners are also susceptible to galling, a form of adhesive wear in which mating threads seize, whereas zinc plated carbon steel is far less prone to it (Budinski, 2001). This allows the joints to be assembled, taken apart and reconfigured repeatedly using standard M16 hex nuts or tool free wing nuts. M16 Form G washers are used to prevent localised crushing of the birch plywood face veneers. A standard washer concentrates the clamping load over a small area, where it can exceed the compressive strength of the plywood perpendicular to the grain. With an outside diameter of 50 millimetres, the Form G washer provides a bearing area of just over 1,700 square millimetres, spreading the load so that the stress remains below the level at which the timber surface crushes or dishes (Porteous and Kermani, 2013, pp. 235–241). In terms of durability, homes, shops and workplaces are low corrosivity environments, in which zinc plating protects steel for many years (Roberge, 2008, pp. 183–195). Specifying A4 marine grade stainless steel would therefore provide more corrosion resistance than these settings require. BZP metric hardware is also widely available, so replacement parts are easy to find, supporting repair over the life of the furniture and the addition of new components to the system. These widely available and recyclable components allow The SAVARIND Concept system to be assembled, adjusted and reconfigured over a long working life, with joints that remain sound through repeated use. References Bickford, J.H. (1995) An Introduction to the Design and Behavior of Bolted Joints. 3rd edn. New York: Marcel Dekker, pp. 135–142. Budinski, K.G. (2001) 'Resistance to adhesive wear of materials', Wear, 250(1), pp. 22–26. Available at: https://doi.org/10.1016/S0043-1648(01)00609-2 Davis, J.R. (ed.) (1994) Stainless Steels. Materials Park: ASM International, pp. 113–116. Porteous, J. and Kermani, A. (2013) Structural Timber Design to Eurocode 5. 2nd edn. Chichester: John Wiley and Sons, pp. 235–241. Roberge, P.R. (2008) Corrosion Engineering: Principles and Practice. New York: McGraw Hill, pp. 183–195.
