ABSTRACT

To illustrate the methodology proposed by the author the case of unrestrained and simply supported steel beam is analysed in detail. The permanent load g and only one variable load q, both uniformly distributed, are applied to the beam. Member resistance is proportional to the steel yield point, being the random variable with log-normal probability distribution. Steel yield point is reduced if the beam is subject to fire exposure (reduction factors ky,# are assumed according to the standard EN 1993-1-2). Moreover, it is assumed that the steel temperature monotonically rises during fire; nevertheless, at each particular fire moment the member temperature distribution is

always uniform both in considered cross-section and along the beam length. The bending modulus Wpl as well as the reduction factor ky,# are treated as deterministic parameters; however, their variability is added to the global coefficient of variance υR calculated for the resistance:

4 OBTAINED RESULTS

Evaluations of beam critical temperature, completed in the considered example for the ordinary required safety level, are presented in detail in Figure 1.