Local buckling studies of cold-formed steel compression members at elevated temperatures

• Local buckling tests of cold-formed steel columns were conducted at ambient and elevated temperatures up to 700 °C.
• Suitable finite element models were developed and validated using test results.
• Test and FEA results were compared with local buckling capacity predictions from available design rules.
• Ambient temperature design rules can be safely used at elevated temperatures with appropriately reduced mechanical properties.
• Current design rules can be improved by including the effects of non-linear stress-strain characteristics at elevated temperatures.

Cold-formed steel members have been widely used in residential and commercial buildings as primary load bearing structural elements. They are often made of thin steel sheets and hence they are more susceptible to local buckling. The buckling behaviour of cold-formed steel compression members under fire conditions is not fully investigated yet and hence there is a lack of knowledge on the fire performance of cold-formed steel compression members. Current cold-formed steel design standards do not provide adequate design guidelines for the fire design of cold-formed steel compression members. Therefore a research project based on extensive experimental and numerical studies was undertaken to investigate the local buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. First a series of 91 local buckling tests was conducted at ambient and uniform elevated temperatures up to 700 °C on cold-formed lipped and unlipped channels. Suitable finite element models were then developed to simulate the behaviour of tested columns and were validated using test results. All the ultimate load capacity results for local buckling were compared with the predictions from the available design rules based on AS/NZS 4600, BS 5950 Part 5, Eurocode 3 Parts 1.2 and 1.3 and the direct strength method (DSM), based on which suitable recommendations have been made for the fire design of cold-formed steel compression members subject to local buckling at uniform elevated temperatures.