Calculating the buckling strength of steel plates exposed to fire

The local buckling capacity of fire-exposed steel cross sections is affected by the reduction in strength and stiffness associated with an increase in steel temperature. Using a stress-based approach, simple continuous equations that account for these reductions are proposed in this paper to calculate the ultimate strength of thin steel plates (i.e. idealized webs and flanges) at elevated temperature. Calculations made using the proposed equations show good agreement with computational results for a range of temperatures, boundary conditions, and loading scenarios. Comparisons with the results of previously published experiments show that the proposed approach provides a conservative prediction of experimentally measured buckling strengths of heated steel sections with thin plates. The proposed equations for calculating ultimate plate strength at elevated temperature offer a significant improvement over current AISC methods, which do not include an explicit temperature-based reduction of buckling capacity. The proposed equations are also a slight improvement over current Eurocode methods, which may become discontinuous for smaller values of plate slenderness. The proposed approach also has greater similarity to current North American standards than those of Eurocode.