Дослідження впливу втрати цілісності вогнезахисного покриття на межу вогнестійкості сталевої балки

Abstract

To solve the main tasks set in the work, the temperature regime of heating the steel beam was determined. The loss of integrity of the fire-retardant coating as a result of the thermal effects of the fire was taken into account. The time of exposure to the standard temperature of the fire and the value of the heating temperature of the steel beam with mineral wool cladding at which it loses its integrity was set. According to the finite element scheme, the steel beam was divided into shell four-node elements of the SHELL type. Five thickness integration points were used in the Belichko-Tsai formulation to calculate the temperature regime. This allowed us to take into ac count the geometric parameters of the cross section of the studied I-beam. After calculation, the obtained results are given 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 the fire. The critical values of the onset of the limit of fire resistance according to the graph of the maximum deflection and the graph of the rate of increase of the deflection are determined. The difference of indicators shows that the time of the limit state of loss of bearing capacity is 70 minutes less, if the loss of fire retardant capacity of mineral wool fire protection due to loss of integrity is not taken into account