Design expression for calculating the resistance of an axially or eccentrically loaded steel column at high temperature

Purpose In this paper a new design expression for calculating the resistance of a steel column under fire exposition has been proposed. The intention is to provide a generic expression valid for column both axially and eccentrically loaded. In addition the novelty and importance of the proposed expression is that it is conservative (unsafe predictions, UP < 5%), and it is especially easy to apply for technicians. Design/methodology/approach The methodological approach was the following: (1) to include in a single expression (that was above all simple) theoretical considerations on different aspects relating to the behavior of a steel column subjected to high temperatures; (2) Evaluate the reliability of the expression found not only with respect to the experimental results, but also in comparison with other calculation expressions also provided by the codes. Findings The author’s aim is also to give a formula which is easy to apply and therefore widely usable by engineers, as the already existing design equations. From the comparison with the test results found in the literature the here proposed expression has found to be (among the expressions considered) not only the most consistent, but also the most conservative, providing 95% of safe predictions. Research limitations/implications In this paper a new design expression for calculating the resistance of a steel column under fire exposition has been proposed. Obviously, the model has some limitations mainly due to the assumptions made: (1) temperature constant across the section and along the length of the steel column, (2) absence of initial curvature, (3) absence of imperfections and (4) absence of local buckling phenomena. Another limitation is the approximation of the buckling length (as a consequence of the constraints). Practical implications It must be highlighted that the novelty and importance of the proposed expression, here proposed as a “design” expression is that it is conservative (unsafe predictions, UP < 5%) and it is especially easy to apply for technicians. Originality/value The value of the research described in this manuscript is, above all, the fact that it has been proposed as an expression that is easy to use also for practical engineers (not only for university researchers). Despite this, it is very accurate, because it was obtained from a careful analysis of different aspects related to the behavior of a steel column when exposed to high temperatures.