Comparative analysis of fire-adapted models for the shear buckling strength of web-posts in castellated steel beams

Web-post buckling by shear is one of the typical failure modes of beams with sequential web openings, as well as the preponderant failure mode in fire. With the increase of the temperature, the modulus of elasticity of steel reduces faster than its resistance, so the beam becomes more susceptible to failure due to instability. This paper presents a comparison between existing formulations for determining the shear buckling strength of web-posts and validated numerical results. The objective was to assess if they are valid in fire conditions, with the modification of the modulus of elasticity and yield strength of steel according to each temperature considered in the analysis, using the statistical evaluation method present in EN 1990:2002. It was evident that the formu-lations analyzed are satisfactory at ambient temperature but most of them need adjustments when applied in fire.