JUSTIFICATION OF THE METHOD OF IDENTIFYING THE MECHANICAL CHARACTERISTICS OF CONCRETE OF REINFORCED CONCRETE BEAMS ACCORDING TO THE RESULTS OF FIRE TESTS
Abstract
Concrete is the most popular and widespread building material in the world. No construction of a private house or the construction of monolithic reinforced concrete structures is complete without concrete. The strength characteristics of concrete are slightly inferior to natural stone, and in some parameters even exceed it.
The purpose of the work is to clarify the mechanical characteristics of concrete during its heating under conditions of exposure to the standard fire temperature regime. The proposed method of identifying the mechanical characteristics of concrete is based on the reproduction of the temperature distribution in the cross-sections of reinforced concrete beams based on the results of point temperature measurements during fire tests. In this method, the equations of equilibrium are used, compiled using the deformation mathematical model of the stress-strain state. Based on the obtained experimental data, the temperature distributions were reproduced using the proposed interpolation method. According to the obtained temperature distributions and the proposed mathematical apparatus, the coefficient of reduction in the concrete strength of reinforced concrete beams during fire tests was identified, the maximum deflection of two sample reinforced concrete beams was determined, and using a deformation model based on the use of equilibrium systems of internal layers in the cross section of reinforced concrete beams, the coefficient of reduction of strength of concrete under the condition of exposure to the standard fire temperature regime was specified. The presented curves of the value of the coefficient of reduction of concrete strength according to the proposed method and according to the recommendations of Eurocode 2 indicate the presence of a deviation between these indicators. The resulting refined dependence of the concrete strength reduction factor is the basis for improving the calculation method for assessing the fire resistance of reinforced concrete crossbars based on deformation models.
