Коэффициенты учета влияния теплотехнических характеристик арматуры на огнестойкость сжатых железобетонных элементов

Abstract

Предложено модифицировать методику расчета огнестойкости железобетонных конструкций с учетом влияния на показатели их огнестойкости теплотехнических характеристик арматуры. В основу модификации методики положены корректирующие коэффициенты К1 и К2, полученные в результате экспериментальных исследований и численного анализа. Доказано повышение огнестойкости железобетонных элементов при увеличении содержания в них арматуры от 3,5 до 8,0 %. Methods of calculation justification of the bearing capacity of columns, with different percentages of reinforcement, have been developed, tested and fixed in domestic and foreign design standards. The calculation of the fire resistance of columns with small percentages of reinforcement has also been tested and is performed in accordance with the methodology. However, for columns with an increased percentage of reinforcement (more than 3.5 %), the use of the standard technique can lead to excessive reserves and overspending of materials, since when determining the cross-sectional temperature fields for calculating fire resistance, the method does not take into account the thermal influence of reinforcement. Previously conducted by the author experimental studies of cross-section heating temperatures and fire resistance of compressed reinforced concrete elements allowed a comparative analysis of the studied parameters with the results of numerical calculations, the obtained comparable convergence allowed further calculations of reinforced concrete elements in the Abaqus software package with different geometric dimensions and percentage of reinforcement. According to the results of the numerical study, it was determined that when reinforcing reinforced concrete elements up to 3.5%, the influence of thermal characteristics on the strength resistance of reinforced concrete elements under fire is practically absent, but when reinforcing from 3.5 % to 8 %, the greatest influence of thermal characteristics of reinforcement inclusions on the bearing capacity of the elements is manifested. At the same time, it is also recorded that this positive effect disappears when reinforcing elements of more than 8 %, which is due to the significant bearing capacity of reinforcing bars (when compared with concrete), which is 50 percent or more.