Fire local stability of steel I-sections under simple load cases

The local buckling behavior of hot-rolled and welded I-sections under simple load cases at elevated temperatures is investigated numerically through extensive numerical analysis. Advanced shell Finite Element (F.E.) models are firstly developed and validated against existing experimental data for I-sections under fire conditions and then further used to carry out extensive parametric studies in order to consider a wide range of cross-section geometries, steel grades and temperatures. The reference F.E. results are subsequently compared with resistances predicted by the current European provisions. It is shown that these design provisions, which rely on similar cross-section classification and on the Effective Width Method (E.W.M.) just as room temperature rules, provide over-conservative and scattered resistance predictions to various extents. Therefore, an alternative design method - the Overall Interaction Concept (O.I center dot C.) - is proposed in this paper for I-sections at elevated temperatures. The O.I.C. is evidenced to provide more accurate, consistent and straightforward resistance predictions than current standards. Eventually, the reliability level of the O.I.C.-based proposals and of the current European provisions is evaluated.