Mathematical Description of the Process of Resistance to the Thermal Impact of Reinforced Concrete Columns

The article presents the results of analysis of experimental data on the variation in the degree of section reinforcement, the intensity of power stresses, the width of the column cross-section, the thermal diffusion of concrete under the conditions of exposure to a standard fire, the change in the compressive strength of concrete - on the basis of which a mathematical model of the process of reducing the load-carrying capacity of a column was developed; a mathematical description of the onset of the limiting state of a reinforced concrete column on the basis of a loss of bearing capacity in the conditions of a fire; the poly-parametric equation for evaluating the design fire resistance of the reinforced concrete column has been derived, and the influence of the distinctive design parameters (the degree of reinforcement of the section, the hollowness, the depth of the reinforcement, the longitudinal bending) on the design limit of the fire resistance of the reinforced concrete column of the building is taken into account. Analytical formulas are obtained for estimating the indices of fire resistance of a column from the value of the standard resistance of concrete to compression and the index of its thermal diffusion. (paper)