Post-fire behaviour and improving the performance of hot rolled open sections subjected to standard fire exposure

This paper presents an experimental and numerical analysis considering the effect of standard fire conditions on the post-fire strength of hot rolled hollow steel sections, where the influence of passive protection, cooling conditions and micro structural changes were also analysed with precision. Square, rectangular and circular shaped specimens were considered for the investigation. Cementitious perlite coating was used to improve the fire resistance of sections exposed to elevated temperature following the ISO 834 standard fire curve. Investigations were performed to evaluate the influence of fire conditions on the axial load capacity, deformation, stress-strain behaviour, yield stress, ultimate stress, and elastic modulus of sections. Finite Element Models (FEM) were developed and validated with experimental results. A detailed micro structural analysis was done with keen observation to assess the physical characteristics by scanning electron microscope (SEM) and image analysis. As expected, passively protected specimens show significantly higher post-fire resistance. In the case of water cooling, the post-fire capacity of sections decreased by approximately to 10–15%. Micro cracks were identified along with a greater proportion of pearlite in the micro structures of water cooled specimen