Refining a tabular method for assessing the fire resistance of reinforced concrete structures

This paper reports the analysis of fire resistance assessment methods of building structures. Based on the results, it was established that conducting fire tests is not expedient and harmful to the environment. The use of estimation fire resistance assessment methods for reinforced concrete staircases is not considered possible due to the lack of appropriate tables with fire resistance classes for the tabular method. The use of the estimation zone method is also impossible because of the lack of temperature nomograms of temperature distribution during exposure to the standard fire temperature regime. There are also no described procedures for applying the estimation refined method for reinforced concrete staircases. So, using mathematical models, the existing type of reinforced concrete staircase was reproduced. Employing the finite-element method, the behavior of reinforced concrete stairwells under the influence of fire was investigated. Based on the results of these experiments, it was analyzed which structural geometric parameters of reinforced concrete stairwells have the greatest influence on their fire resistance. In this way, three independent, most significant geometric parameters of reinforced concrete stairwells were established – the height of the solid base, the thickness of the protective layer of the lower row of reinforcing bars, and the length of the span. Therefore, the ranges of the most significant structural geometric parameters of reinforced concrete stairwells were used to build a regression dependence of the fire resistance limit on these parameters in order to design a full factorial numerical experiment. After proving the adequacy of the results obtained according to the regression dependence, tables were constructed with the geometric parameters of reinforced concrete stairwells to determine the compliance of these structures with the required fire resistance class. The use of these tables will make it possible to reduce the risks of threats to human life and health during a fire by determining the possibility of using these structures with a guaranteed fire resistance class during desig