The response of high strength S700 MC steel after fire exposure

High-performance steels are widely utilized in bridges and high-rise buildings since they have superior properties such as a high strength/weight ratio and good earthquake resistance. However, exposure to high temperatures affects the strength and stiffness of these materials. For this purpose, the assessment of post-fire behavior of highperformance steels is a crucial issue from the standpoint of safety. Thus, a combined experimental and parametric study was performed to evaluate the fire damage of buildings made of high strength steels. First, tensile test coupons cut from high strength S700 MC steel sheets with thicknesses ranging from 2.5 mm to 15 mm were subjected to different temperatures up to 1200 degrees C. These specimens were then released to cool to normal room temperature by natural air cooling before being tested. A series of tensile tests was conducted on these coupons to identify the parameters of post-fire mechanical behavior such as the elastic modulus, yield strength and ultimate tensile strength. Test results demonstrated that the mechanical behavior of high strength S700 MC steel after exposure to fire changed considerably when the heating temperature exceeded 600 degrees C. Thus, based on experimental findings, a new set of equations has been developed to estimate changes in the mechanical parameters of high strength S700 MC steel. These novel predictive equations allow the accurate evaluation of buildings made of high strength S700 MC steel after exposure to fire events. Furthermore, these proposed empirical equations are general and are valid for high strength steels with yield strengths of up to 700 MPa. The proposed equations are presented in a form that is immediately useful for adoption into practical design standards.