The thesis discusses the calculation of fire resistance of a steel portal frame; in terms of the content, it is divided in two sections. In the first section fire resistance of a structure is determined in line with the simplified calculation method in accordance with the SIST EN 1993-1-2 standard and by applying the software SCIA Engineer 16.0. In the second section, fire resistance of a structure is verified against the advanced method, by the use of software POŽAR. In both analyses, fire resistance has been calculated for a standard-temperature fire scenario ISO 834 and a "natural" (parametric) fire scenario. Parametric fire curves have been determined by applying software Ozone V2.2 for two fire sections, specifically, for warehouse premises and for offices. Several situations are examined which include analyses based on ISO 834 fire curve and parametric fire curves. The aim of the thesis is to present any potential differences between the simplified and the advanced calculation method and to present the impact of input parameters for the calculation of parametric fire curves in regard to fire resistance of the steel construction in question.