The model fire test of reinforced concrete components often necessitates a furnace temperature-rising curve markedly exceeding that of the prototype, as prescribed by conventional similarity theory. Nonetheless, this prerequisite may occasionally render the model fire test unfeasible due to exceeding the heating capacity of the furnace. In response to this challenge, the present study conducts finite element analysis (FEA) on geometrically similar, reinforced, square concrete columns of various sizes exposed to fire from two or three sides, using the ISO 834 standard fire curve for all columns. The fire resistance results from FEA are utilized to derive similarity relationships for the time scale of the model to prototype columns. The similarity in the thermal-mechanical response of the model and prototype columns under the proposed time scale is evaluated and validated using experimental data from this study and previous research. The findings indicate that good similarity between the mechanical response and fire resistance of the model and prototype columns can be attained by normalizing the time scale using s1.19 for 2-sided heating and s1.29 for 3-sided heating, where s represents the geometric scale factor of model to prototype, the data from the model column under standard fire effectively predicts the axial deformation development and fire resistance of the prototype column.