Experimental and numerical studies of fire exposed lipped channel columns subject to distortional buckling

• Published in: Fire safety journal Vol. 70; pp. 34 - 45
• Main Authors: Gunalan, Shanmuganathan, Mahendran, Mahen
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2014; Elsevier
• Subjects: Ambient temperature; Applied sciences; Building structure; Building technical equipments; Buildings; Buildings. Public works; Channels; Cold-formed steel structures; Columns (structural); Construction (buildings and works); Distortional buckling; Exact sciences and technology; Exposed temperature; Exposure; finite element analysis; Fire behavior of materials and structures; Fire protection; Fires; High temperature; mechanical properties; Metal structure; Post-fire mechanical properties; prediction; residential housing; Residual strength; steel; Strength of materials (elasticity, plasticity, buckling, etc.); Structural analysis. Stresses; Structural steels; Cold-formed steel structures; Exposed temperature; Post-fire mechanical properties; Distortional buckling; Metallic structure; Cold forming; Mechanical properties; High temperature; Steel; Experimental study; Forecast model; Finite element method; Column; Fires; Numerical simulation; Buckling; Comparative study; Ultimate load
• ISSN: 0379-7112
• DOI: 10.1016/j.firesaf.2014.08.018

Cold-formed steel sections are commonly used in low-rise commercial and residential buildings. During fire events, cold-formed steel structural elements in these buildings are exposed to elevated temperatures. Hence after such events there is a need to determine the residual strength of these structural elements. However, only limited information is available in relation to the residual strength of fire exposed cold-formed steel members. This research is aimed at investigating the residual distortional buckling capacities of fire exposed cold-formed steel lipped channel sections. A series of compression tests of fire exposed, short lipped channel columns made of varying steel grades and thicknesses was undertaken in this research. Test columns were exposed to different elevated temperatures up to 800°C. They were then allowed to cool down at ambient temperature before they were tested to failure. Suitable finite element models of tested columns were also developed and validated using test results. The residual compression capacities of tested columns were predicted using the ambient temperature cold-formed steel design rules (AS/NZS 4600, AISI S100 and Direct Strength Method). Post-fire mechanical properties obtained from a previous study were used in this study. Comparison of results showed that ambient temperature design rules for compression members can be used to predict the residual compression capacities of fire exposed short or laterally restrained cold-formed steel columns provided the maximum temperature experienced by the columns can be estimated after a fire event. Such residual capacity assessments will allow structural and fire engineers to make an accurate prediction of the safety of buildings after fire events. This paper presents the details of these experimental and numerical studies and the results. •Conducted distortional buckling tests of cold-formed steel columns after being exposed to elevated temperatures.•Developed suitable finite element models and validated using test results.•Columns were able to regain 90% of their original capacities if the exposed temperature was below 500°C.•Ambient temperature design rules can be safely used to predict the residual capacities using post-fire mechanical properties.•Proposed a new set of equations to predict the residual distortional buckling capacities.