This thesis studies the buckling behavior of I-shaped steel columns under the effect of thermal gradients. The mechanical properties of steel decay signicantly with increasing temperature. Therefore, in case of a re, the buckling resistance of steel columns is considerably reduced due to the decrease in the modulus of elasticity and yield strength. Furthermore, in a realistic re scenario, temperature gradients develop throughout the cross-section and throughout the column's length. However, the design guidelines in Eurocode 1993-1-2, as well as in other leading construction codes, specify that in the case of a non-uniform temperature distribution the column's buckling resistance must be determined by considering a uniform temperature distribution considering the maximum temperature in the cross-section. The objective of this thesis is to assess the reliability of the provisions given by the Eurocode for elevated temperature design in the presence of temperature gradients. A series of finite element models were created for five different cross-sections and analyzed at room temperature, uniform elevated temperature and non-uniform temperature along the cross-section. From the uniform elevated temperature analysis, a buckling curve for elevated temperature was derived. The finite element analysis results for the models under the effect of temperature gradients showed better agreement with this FEM-derived buckling curve than with the Eurocode provisions, which were shown to be over-conservative for the case of a temperature gradient along the column's weak axis. The FEM results were also compared to the results obtained with the American and Australian building codes….