EVALUATION OF THE NECESSARY FIRE PROTECTION THICKNESS FOR STEEL STRUCTURES UNDER DIFFERENT FIRE TEMPERATURE-TIME CURVE
Abstract
The purpose of the conducted research was to identify unsolved issues regarding the assessment of the required fire protection thickness for steel structures under conditions of fire exposure at different fire temperature-time curve and to determine directions for further research. In order to achieve this goal, the task of determining and analyzing the current requirements for the fire resistance of steel structures, the applicable methods for assessing the fire resistance of these structures and the required thickness of their fire protection, the available data on the significance of this thickness, obtained for different fire temperature-time curve, was solved.
According to the results of the research, it was found that in accordance with European and national standards and state building codes, fire resistance requirements and fire resistance classification of load-bearing structures without enclosing functions, such as beams and columns, are established only for conditions of fire exposure under a standard temperature/time curve. At the same time, Eurocodes 1, 3 and national standards provide for assessing the fire resistance of such steel structures also according to the temperature-time curves of hydrocarbon and external fires. Methods of determining the required minimum thickness of fire protection for steel structures are implemented in European and national standards also only for conditions of fire exposure under a standard temperature/time curve. The procedure for determining this thickness for the conditions of fire exposure according to the temperature-time curves of hydrocarbon and external fires is uncertain. Also uncertain is the issue of dependencies regarding the required minimum thickness of fire protection for steel structures that are subject to fire exposure at other than the standard temperature-time curve, nominal fire temperature-time curves, as well as data on the relationship between the values of this thickness obtained under different nominal temperature-time curves. Such uncertainty gives rise to potentially interesting areas of further research, which are focused on identifying the influence of nominal fire temperature-time curves on the required minimum thickness of fire protection for such steel structures as beams and columns, for wide ranges of changes in the thermophysical properties of applicable fire protection materials, the critical temperature of steel, the cross-section coefficient and the time interval of preservation of fire resistance.
