INVESTIGATION OF THE FIRE RESISTANCE LIMIT OF STEEL BEAM IN CASE OF LOSS OF INTEGRITY OF FIRE PROTECTIVE COATING
Abstract
In this article to solve the main problems the temperature regime of heating the steel beam was determined, which took into account the fact of loss of integrity of the fire-retardant coating due to the thermal effects of fire.
When calculating the temperature, the time of exposure to the standard temperature of fire and the value of the heating temperature of the steel beam with mineral wool coating at which the latter loses its integrity were determined. A graph of the temperature regime of heating a steel beam with mineral wool fire-retardant coating (under the influence of the standard temperature regime of fire) without taking into account and taking into account the loss of integrity of fire-retardant mineral-wool coating is constructed. Starting from 45 s, the temperature of the steel beam noticeably rises and in almost 5 minutes approaches the temperature curve of the standard temperature regime of the fire, which indicates the failure to perform the fire-retardant function of the coating due to loss of integrity.
According to the obtained heating regime, the value of the limit of fire resistance of the steel beam under the condition of loss of integrity of the fire-retardant coating depends on the stress-strain states in the steel beam. Given the geometric parameters of the cross Belichko-Tsai. After the calculation, the corresponding results were obtained in the form of graphs of changes in the maximum deflection of the beam and the rate of increase of the maximum deflection depending on the time of exposure to the standard temperature of fire. The critical values of the boundary of the fire resistance limit on the graph of maximum deflection and on the graph of the rate of increase of deflection are determined. The difference of indicators shows that the time of the limit state of loss of bearing capacity is 70 min less, in case of not taking into account the loss of fire-retardant capacity by mineral wool fire-protection due to loss of integrity.
