Abstract
Methods for calculating the fire resistance of steel-reinforced concrete slabs made using profiled steel sheets under the influence of a standard temperature regime for more than 120 minutes are considered and analyzed. Research has been carried out to determine the heating parameters and the stress-strain state of steel-reinforced concrete slabs made using profiled steel sheets under fire conditions for more than 120 minutes. The results of this study allow to obtain indicators of temperature distribution for assessing the fire resistance of such structures for fire resistance classes above REI 120. Accordingly, the results obtained are a scientific basis for improving the existing method for calculating the fire resistance of steel-reinforced concrete slabs made using profiled steel sheets. The temperature distribution in the cross-section of structures was obtained using a general theoretical approach to solving the problem of heat conduction using the finite element method. Using the obtained temperature distributions, the parameters of the stress-strain state were determined based on the method of limiting states. To carry out the calculations, appropriate mathematical models were created that describe the effect of the standard temperature regime of a fire, to determine the temperature distribution at every minute in the sections of steel-reinforced concrete slabs with profiled steel sheets. A method is proposed for dividing the section into zones to take into account the decrease in the indicators of the mechanical properties of concrete and steel. A simplified method for the design assessment of steel-reinforced concrete slabs made using profiled steel sheets is proposed, which is consistent with the current EU standards and can be effectively used to analyze their fire resistance when establishing their compliance with the fire resistance class REI 120 and higher.
Highlights
The current state of the construction industry is characterized by the intensification of the development and implementation of innovative technical solutions in all areas of construction
For the analysis of the onset of loss of integrity, such methods are generally limited and insufficiently developed [11]. This largely applies to steel-reinforced concrete slabs with profiled steel sheets, the design of which determines that the profiled sheet is directly exposed to fire and this affects their bearing capacity in such conditions
The following objectives were set: – to investigate the nature of the time of the onset of the limiting state of thermal insulation capacity in steel-reinforced concrete slabs with profiled steel sheets using a simplified method; – to calculate the temperature distributions in the sections under the thermal effect of the standard temperature regime of the fire according to the refined calculation method; – to construct regression dependences for assessing the fire resistance of steel-reinforced concrete slabs with profiled steel sheets according to the limiting state of the loss of bearing capacity
Summary
The current state of the construction industry is characterized by the intensification of the development and implementation of innovative technical solutions in all areas of construction. The danger of fires at construction sites is characterized by the risk of the appearance and action of dangerous fire factors, with which it is associated and which directly relates to the possibility of destruction of building structures or their loss of their enclosing functions In such conditions, the fire resistance of building structures plays an important role in the overall assessment of the fire safety of construction facilities. For the analysis of the onset of loss of integrity, such methods are generally limited and insufficiently developed [11] This largely applies to steel-reinforced concrete slabs with profiled steel sheets, the design of which determines that the profiled sheet is directly exposed to fire and this affects their bearing capacity in such conditions. For the use of steel-reinforced concrete slabs with profiled steel sheets in fireproof floor structures with increased requirements for their fire resistance, it is relevant to study and develop simplified calculation methods for assessing their fire resistance
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