Finite Element Investigation on the Behaviour of Open Web Steel Beams Subjected to Fire

This paper presents a numerical investigation on the behaviour of open-web steel beams under high temperatures rise due to fire using finite elements simulations with ANSYS software. Cases of study for solid parent steel elements as well as castellated and cellular beams are considered and take into account uniform and transient temperature rise, material and geometric non-linear behaviour. Input fire is the standard temperature-time curve ISO834 fire model and thermal and mechanical analyses are done using the effect of temperature dependent material properties according to Eurocode3 part1--2 recommendations for mechanical steel properties reduction. FE models which estimate failure temperatures are presented for two most commonly used types of web opening shapes including, hexagonal and circular for simply supported beams under uniformly distributed mechanical loading. The study shows that the numbers of web-openings and cells as well as their shapes are critical for the behaviour of castellated steel beams under fire conditions. Results are related to temperature profiles in steel beam cross-sections, variation of displacements with respect to temperature change and critical temperatures.