Assessment of mechanical properties of cold formed steel material at elevated temperature

Abstract

Fire accident is considered as the one of most severe environmental hazards for buildings and infrastructures. Cold formed steel (CFS) beam has been used extensively as the primary load bearing structural member in many applications in building construction dues to high production, fabrication and assembling efficiencies in construction. Consequently, material used must show a high level structural integrity and stability throughout a long period of time to perform well in fire incident. Hence, assessments of the materials’ properties are crucial in order to predict the performance of the structure during fire incidents; therefore, the tensile coupon tests of CFS are according to BS EN 10002-1:2001 and the G450 CFS material with 1.90 mm thickness was used in this study. The elastic modulus, yield stress, correspondent percentage strain at yield stress, ultimate stress, and correspondent percentage strain of ultimate stress were 200.30 GPa, 540.50 MPa, 0.478%, 618.80 MPa, and 8.701% respectively. Furthermore, the results of the ambient temperature test were used to assess the mechanical strength of CFS at the elevated temperatures. The discussion of material properties is based on EC3-1-2 and proposed models from other researches, while the main material properties discussed are the stress-strain curve, elastic modulus and yield strength at elevated temperatures was determined. It was found that the actual elastic region was slightly lower than the predicted EC3-1.2 at ambient temperature, but it was well fit with two other studies. Besides that, the actual material properties experienced a strain hardening after yielding and reached a maximum stress of up to 618 MPa while the predicted EC3-1.2 constant value of the yield stress after yield was until 15.0% of the strain, meanwhile, other two studies had fitted the ambient tensile test up to the ultimate stress which fitted until 2.0% strain level.