Typical applications
The range of application of cold-formed steel structures is considerable and increasing.
The low cost, ease of manufacture and controlled quality encourage the development of innovative uses. The use of factory manufactured building components is one of the principal agents in the industrialisation of the construction industry, characterised by the shift from site based operations to prefabrication and on-site assembly.
The development of new manufacturing processes offer the opportunity for larger structural frames and volumetric or modular buildings
Typical applications of cold-formed steel in buildings:
- cladding panels and decking
- light weight structural sections
- stud frames and other fabricated structures
Cladding panels and decking
Cladding panels and decking are the most widespread uses of cold-formed products.
Corrugated sheeting is perhaps the oldest use of cold-formed steel sheet used in buildings. The flat sheet is folded into a series of ribs forming troughs and crests to produce lightweight load bearing panels.
Roll forming now is used to produce a wide range of profiles for both cladding and decking. With regard to structural behaviour both applications are identical, however the details may change for other reasons. For example: in the use of profiled steel sheet in low pitch roofing protection of the side lap against water penetration may be critical whereas in composite steel decking a shape that bonds effectively with concrete is more important.
Brake pressing is also used to produce other cladding panels, such as cassettes. Individual sheets are notched at their corners and folded into panels with return edges.
The roll-forming process may also be incorporated with other processes to produce composite panels, where an insulated core is used to bond an inner and outer steel sheet, creating a very rigid cladding panel with a high thermal performance.
The steel decking used in composite floor construction has revolutionised the construction of multi-storey steel frame and is a critical part of fast track building. Innovation in this are continues with the development of deeper and longer spanning decks.
Lightweight steel sections
Lightweight cold-formed steel sections are used as secondary steel sections and as primary elements in fabricated steel panels and trusses. Typical sections are C or Zed shaped.
Next to cladding lightweight structural sections Zed and C-sections form the other major use of cold-formed steel in buildings. These are used extensively as purlins and sheeting rails to support cladding and in fabricated structures: stud framing for houses, partitions, trusses and frames. Cold-formed steel purlins have replaced the use of hot rolled steel and timber in metal clad buildings.
These are now standard components. Many of the sections that are now used have been carefully developed to optimise both structural performance and construction. Purlins range in depths from 120 to 340 millimetres and can span up to 15 metres between primary structures.
Structural sections are also used in curtain walling in multi-storey buildings. A big advantage is the replacement of the masonry back up wall, used to support the cladding panels with a lightweight stud frame. The total load on the structure is reduced and a wet trade is eliminated and the installation of the cladding is faster. The ICMB building at Edinburgh University is a good example.
Fabricated structures
Cold-formed steel elements are also used to produce larger fabricated structures.
Cold-formed steel elements, C sections and Zed sections, are often used to produce larger structural units such as wall panels. As the elements themselves are light and efficient the fabrication methods become a particularly important part of the overall cost. The stages in the fabrication process are:
- Cutting, notching and drilling of cold-formed steel elements.
- Assembly of components in jig for connection.
- Connection elements together
- Removal of fabricated structure from jig
- Additional corrosion protection (if needed)
