Experimental investigation of post-fire mechanical properties of cold-formed steels |
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| Affiliation: | 1. College of Civil Engineering, Tongji University, 200092 Shanghai, China;2. Department of Structural Engineering, Faculty of Civil Engineering, Delft University of Technology, P. O. BOX 5048, 2600GA Delft, The Netherlands;1. State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China;2. College of Civil Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China;1. State Key Laboratory for Geomechanics & Deep Underground Engineering, CUMT, Xuzhou 221116, China;2. Key Laboratory of Building Fire Protection Engineering and Technology of MPS, Tianjin, 300381, China;3. School of Civil Engineering, Southeast University, Nanjing 210096, China;1. State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin 300072, China;2. Key Laboratory of Coast Civil Structure Safety of China Ministry of Education, Tianjin University, Tianjin 300072, China;3. Department of Civil Engineering, Tianjin University, Tianjin 300072, China |
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| Abstract: | Cold-formed steel members are widely used in residential, industrial and commercial buildings as primary load-bearing elements. During fire events, they will be exposed to elevated temperatures. If the general appearance of the structure is satisfactory after a fire event then the question that has to be answered is how the load bearing capacity of cold-formed steel members in these buildings has been affected. Hence after such fire events there is a need to evaluate the residual strength of these members. However, the post-fire behaviour of cold-formed steel members has not been investigated in the past. This means conservative decisions are likely to be made in relation to fire exposed cold-formed steel buildings. Therefore an experimental study was undertaken to investigate the post-fire mechanical properties of cold-formed steels. Tensile coupons taken from cold-formed steel sheets of three different steel grades and thicknesses were exposed to different elevated temperatures up to 800 °C, and were then allowed to cool down to ambient temperature before they were tested to failure. Tensile coupon tests were conducted to obtain their post-fire stress–strain curves and associated mechanical properties (yield stress, Young׳s modulus, ultimate strength and ductility). It was found that the post-fire mechanical properties of cold-formed steels are reduced below the original ambient temperature mechanical properties if they had been exposed to temperatures exceeding 300 °C. Hence a new set of equations is proposed to predict the post-fire mechanical properties of cold-formed steels. Such post-fire mechanical property assessments allow structural and fire engineers to make an accurate prediction of the safety of fire exposed cold-formed steel buildings. This paper presents the details of this experimental study and the results of post-fire mechanical properties of cold-formed steels. It also includes the results of a post-fire evaluation of cold-formed steel walls. |
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| Keywords: | Cold-formed steel structures Post-fire mechanical properties Exposed temperatures LSF walls and floors |
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