ABSTRACT
The results of research pertaining to the determination of imperfections influence on failure temperature for non-uniformly heated steel plate girders with Class 4 sections are presented in this paper. Considered girders are characterized by high total section height to width ratio, remaining between 3.7 and 5.2. At the same time, analyzed beams are unrestrained and susceptible to lateral-torsional buckling. Three different cross-sections and two common steel grades (S235 and S355) have been taken into consideration. Load level equal to 50% of load bearing capacity at room temperature has been applied and this study is limited only to beams subjected to uniform bending. Additional comparisons have been provided depending on whether load bearing capacity at ambient temperature was calculated using FEM or according to standard recommendations. Finally, considered beams have been analyzed assuming various amplitudes of geometrical imperfections and various levels of residual stresses. Based on conducted experimental and numerical studies, influence of imperfections on failure temperature of non-uniformly heated steel plate girders is discussed. It is shown that for some cases analyzed imperfections have significant impact on failure temperature and that they cannot be neglected. At the same time, high quality execution of steel structure may result in increased fire resistance.
