高温火直接作用下钢梁抗火性能试验研究

为研究高温火直接作用下钢梁的抗火性能，对其进行了高温火直接作用试验；同时，以受热时间作为变化参数，对比分析了高温火直接作用和按ISO 834标准升温过程钢梁的轴力、跨中挠度及耐火时间。结果表明：高温火直接作用与按ISO 834标准升温下，钢梁破坏端面的微观组织及升温过程的受力和变形存在明显差异；无论有无防火涂层的保护，当温度800℃时，高温火直接作用下钢梁的最大轴力比按ISO 834标准升温的增大76.9%以上；同时，防火涂层厚度对钢梁的耐火时间也有影响，无防火涂层时，钢梁的耐火时间小于20min；有防火涂层保护时，随防火涂层厚度增厚，两种高温作用下，钢梁的耐火时间相近，但防火涂层厚度不足15mm时，耐火时间相差20%以上；当防火涂层厚度为15mm时，在温度约800℃高温火直接作用下，其耐火时间为26min。

Experimental research on fire resistance of steel beamdirectly acted by fierce fire

To investigate the fire resistance of steel beam directly acted by fierce fire, fire tests were conducted considering various heating time. The axial force, deflection at mid-span and the fire resistance time between directly acted by fire and at elevated temperature according to ISO 834 standard were compared. The results show that there are large differences in microstructure, axial force and deformation between steel beams under direct fire and standard ISO 834 heating procedure. Whether there is a protective coating or not, the maximum axial force produced by the direct action of fire at 800℃ is over 76.9% larger than that when heated according to ISO 834 standard. Meanwhile, the thickness of the protective coating also has a large effect on its fire resistance. For a steel beam, when there is no protective coating, its fire resistance time is less than 20 minutes. When there is protective coating for the beam and the thickness of coating is increased, their fire resistance time is close, but the difference is more than 20% when the thickness of protective coating is below 15mm, and the fire resistance time is 26 minutes at 15mm of proptecting coatings when the beam is directly acted by fire at about 800℃.