Comparative study of analytical formulae for the fire resistance of steel beam-columns

This paper investigates the difference between the buckling formulae published in the
Eurocode 3 part 1.2 and the recommendations made in the final report of the Buckling Curves
in Case of Fire (BCCF) research project. This study compares the critical temperatures
obtained with both formulations to assess the impact on the fire endurance of steel columns
subjected to axial compression and bending. An extensive comparison of the ultimate
temperatures obtained with both formulations has been performed (382 profiles, buckling
about the strong and weak axis, 12 column lengths, 6 M/N ratios and uniform and triangular
bending moment distributions). Failure temperatures between 400°C and 860°C have been
considered. The formulations are also compared with Finite Elements (F.E.) calculations
performed for a S235 HEA 200 at 600ºC. This analysis shows that for buckling about the
strong axis the BCCF method is better than the EC3 but for buckling about the weak axis the
EC3 predicts failure temperatures closer to the F.E. model than the BCCF formulation.
Finally, the ultimate temperatures predicted by the two formulations have also been compared
with experimental results from the database SCOFIDAT. This comparison shows that there is
no major difference between the two formulations for small and large bending moments. This
study concludes that the EC3 and BCCF formulations are generally equivalent and that either
formulation can be used.