Finite element numerical evaluation of elliptical hollow section steel columns in fire

To complement previous experimental studies on the performance of unprotected Elliptical Hollow Section (EHS) steel columns, under the hydrocarbon fire curve, a numerical analysis has been performed and outlined in this paper. A three-dimensional Finite Element Method (FEM) model has been developed and calibrated against 12 experiments, comprising of six unrestrained and six axially restrained EHS columns of two slenderness, λz=40.1 and λz=50.8. The EHS temperature profiles and axial displacements, measured under three different loading levels, (αL=0.3, 0.45 and 0.6) were utilised in the calibration process. The mechanical and thermal properties for carbon steel at elevated temperatures, detailed in the Eurocode standard EC3 Part 1–2, design of steel structures [1] have been applied. Axial displacement charts illustrate that a close agreement between the FEM model and the experiment results was achieved, while highlighting how critical the thermal expansion coefficient and geometric imperfection was during the calibration process. Ultimately, the paper will detail appropriate recommendations for the thermal analysis of unfilled Elliptical Hollow Section steel columns, of steel grade S355J2H, and provide the platform for comprehensive parametric fire investigations to commence.

► Experimental study exploring the performance of 12 Elliptical Hollow Section (EHS) steel columns under Hydrocarbon fire.
► Two EHS section types with slenderness 40.1 and 50.1 were compared under three different loading levels.
► The effect of axial restraint was evaluated against unrestrained columns.
► An FEM model was calibrated using Eurocode three parameters and collated experiment data.
► The calibration process is described with thermal analysis recommendations provided for EHS columns.