The fire resistance of reinforced concrete columns can be checked, according to EN 1992-1-2 [1], considering three methods presented in the form of tables: Method A, Method B and Method C (or Method of estimated curvature). In this paper is presented a study developed in order to verify the influence of two parameters required for the application of these methods: the reduction factor, ηfi, and the load level at normal temperature conditions, n. The methods referred in the previous paragraph were applied to the 14124 reinforced concrete columns inserted in the structures of 63 buildings, designed for different types of occupations and licensed before 2007, in Portugal. The fire resistance classes, defined for the different occupations, vary from R30 to R180. The reduction factor values were calculated for each project and the load level for each column. As it was observed, the reduction factor values vary between 0.58 and 0.68 (0.58≤ηfi≤0.68) in ordinary buildings. So, it is recommended the use of values in this interval for the calculation of the axial design load in fire situation, NEd.fi, determined from the design value of the column’s resistance, NRd, namely for the quantification of the initial load to be applied to the columns in experimental tests. Comparing the results, considering the reduction factor, nfi, with design values and with ηfi=0.7, a recommended value in EN 1992-1-2 [1] that can be used as a simplification, it was found that using the second value led to a lower number of columns that satisfied the required fire resistance, corresponding to a percentage between 1,4% and 4,4% of the columns. Regarding the load level, n, calculated for each column, it was found that the most frequent values vary between 0.2 and 0.4.
