Light gauge steel sections (also known as cold-formed
steel sections) are formed by cold rolling thin steel sheet into
shape. Thin steel sheet is typically 0.4 to 3.0 mm thick and
pre-galvanised, such as with a zinc coating, for corrosion prevention.
Light gauge steel sections can be produced in
a large variety of sections and profiled sheeting. In building
construction, traditionally, the commonly used sections are “C” or “Z” shapes
used as roof purlins and side rails to support the cladding in
industrial buildings. Nowadays, light gauge sections have been
widely used as steel frames, trusses, wall partitions, lintels,
floor joists and storage racking etc.
In general, light gauge sections have the advantages
of lightness and high strength-to-weight ratio at ambient temperature.
The strain-hardening caused by the cold-working process increases
the yield strength and ultimate strength of the materials. However,
these characteristics make them more vulnerable to a fire attack
compared to hot rolled sections. Light gauge sections possess
little fire resistance because they would heat up quickly if
directly exposed to fire due to their high section factors. The
increase of mechanical strength, due to strain-hardening, will
also be removed quickly during heating.
However, at present, the performance of light
gauge steel in fire is only briefly described in Eurocodes and
Bristish Standards. This section presents the basic design information
of light gauge steel, followed by some background research studies.