Introduction
Cold-formed steel is used for many applications in construction and building.
A large number of proprietary products use cold-formed steel. For example; cladding and decking, purlins and lintols. Cold-formed steel forms the basis for a number of lightweight pre-fabricated structures such as trusses, stud frame panels and portal frames.
The term cold-formed distinguishes this category of material from hot rolled steel sections, typically universal beams, columns, angles etc., by the manufacturing methods used. Cold-formed sections are produced by bending and shaping flat sheet steel at ambient temperatures.
There is great flexibility in the design using cold-formed steel. A number of innovative engineers and architects have been very successful in producing systems that are both innovative and practical.
Cold-formed steel in either flat plates or coils is the primary raw material for a wide range of industries. We are surrounded by applications, in washing machines, filing cabinets, storage systems, heating and ventilation and cars. About 40% of sheet steel production is used in the construction industry, in cladding, light structural frames and components such as purlins and lintels. The steel sheets can be cold-formed into many different shapes and forms by a variety of manufacturing processes. The different fabrication and forming processes available allow great flexibility in the design of both standard and customised building components and systems. The use of cold-formed steel has played a major part in the development of Hi-tech architecture. Many contemporary architects were greatly influenced by the work of innovators such as Jean Prouvé earlier in this century. In the sixties, systems developed by Eherenkrantz, Williamson and others demonstrated the potential of cold-formed steel in building systems. Steel stud framing is a large and developing area for the use of cold-formed steel.
Ezra Eherenkrantz studied carefully the relationship between the manufacture of building products and their optimum use in buildings. By understanding the discipline and needs of manufacturers and combined with a careful analysis of user requirements he was able to design a series of efficient building systems that took advantage of cold-formed steel structures. Most notable was the SCSD system used for schools.
Eherenhrantz recognised that the performance of off the shelf, standard building components, designed to be used in a range of building types, did not often match the needs of individual buildings. Architects were however limited in their in power to get manufacturers to modify their systems for individual buildings. Eherenkrnatz tackled this problem in the design of the SCSD (Southern California Schools Development) system. He formed a consortium of school authorities, whose combined building programme was large enough to justify the development of components and elements specific to their needs. He designed a system for schools working with manufacturers, to produce tailor made components which optimised both cost and performance. A considerable degree of flexibility in layout and servicing was essential and the structure therefore became a critical part of the development integrating with the air conditioning, lighting and partitions. Welded cold-formed steel trusses were supported off cruciform section columns. The cruciform section was developed to deal with the 'inside-outside' corner detail, using the same connection. The trusses were fabricated from C sections and could span between 9.2 and 23 metres. The depth of the truss was constant to accommodate the services, although the steel thickness reduced as the span reduced. The profiled steel roof deck was attached to the truss during fabrication, folded against the web. On site the deck was opened out and welded to the top of the truss and was used as the top chord of the truss. The system was used on a large number of schools.
During the 60s Gerald A Williamson was responsible for the design and development of innovative cold-formed steel structural systems that combined structure and cladding and used deep profiled steel deck.
The consulting engineers Gerald A Williamson and Partners developed a series of prototype building systems for schools and hospitals. Three important criteria were established, flexibility in planning, integration of cladding, structure and services and the use of industrialised production methods.
In the Computer Centre for the Steel Company of Wales prefabricated panels 4 feet (1.22 metres) wide by 25 feet (7.62 metres) high using cold-formed steel mullions at 2 feet centres combined both structure and cladding. 200 mm deep profiled steel decks, were produced for the floors and were supported on these panels, spanning 4.26 metres onto internal beams and columns. The internal columns were manufactured from four cold formed steel angels, connected to form a lattice arrangement. The overall dimensions of the column were large enough to allow the passage of return air. Thus integrating the structure and services.
