The procedure of fire-resistance calculation for compressed reinforced concrete elements

Abstract

Fire-resistance calculations adopted in the regulatory system (both in the Russian and in European) are based on calculations of isofields of section heatup of structural elements. Heatup isofields for reinforced concrete elements specified in the regulatory system have been obtained by the concrete section calculation not considering inclusions of reinforcement bars. But it is known that accuracy of the fire-resistance calculation of reinforced concrete elements depends on performance accuracy of a thermotechnical calculation. Having performed this calculation the temperature field distribution by element section and strength characteristics depending on it are determined. Temperature distribution by element section depends on such parameters as heat-absorption capacity and thermal conductivity of section parts, section humidity. Within the work the approach to solving the problem of consideration of the actual temperature field when calculating fire-resistance of reinforced concrete and steel-reinforced concrete elements has been reviewed. Calculations of fire-resistance at temperature fields not considering inclusions of reinforcement bars (concrete section) as well as at temperature fields considering reinforcement bar inclusions have been performed. Additional coefficients introduced in the fire-resistance calculation when using Russian and European methods have been calculated for the reviewed section with 600×600 overall dimensions. According to calculation results the change of section bearing capacity upon the calculation considering thermotechnical characteristics of the reinforcement bars has been observed.