Mechanical properties of structural steel exposed to passive fire

Abstract

Non-seismically designed existing reinforced concrete (RC) structures are susceptible to any thermal effect. Indeed, difficulties arise even more in understanding the performance of buildings in fire due to the inherent complexity in the behavior of composite materials at elevated temperatures. This paper deals with the determination of mechanical properties of hot rolled structural steel under thermal effect. A focus on the influence of the passive fire to the structural steel is thus provided. The specimens were firstly heated up to a certain level of temperature (i.e. in a range of 300-700 oC) and then cooled down to room temperature. After that, the dog-bone shape steel tensile test samples were taken from reinforcing bar of RC bond-slip specimens complying with RILEM test method. Dependence of the heating and cooling rate on mechanical properties of S275 type smooth reinforcing steel was identified by either destructive or non-destructive testing methods. Two different techniques including their pros&cons and difficulties in implementing the tests were therefore closely compared. Moreover, major parameters characterizing the behavior of the steel samples exposed to the aggressive fire were compared with the control ones. It is found that not only the ductility in the fire-exposed specimens was essentially different from the ones at ambient temperature but also the deterioration in yield and ultimate strength was considerably affected.