三面受火的方钢管混凝土柱防火保护

FIRE PROTECTIVE COATING OF CONCRETE-FILLED SQUARE HOLLOW SECTIONS BEING EXPOSED TO THREE-SIDE FIRE

实际火灾中钢管混凝土柱可能遭受三面火灾作用。与四面受火相比,受火面的减少将降低构件的整体温度并在构件中产生非均匀温度分布和附加荷载偏心距,使得高温力学性能与四面受火情况有所不同。分析了保护层厚度、荷载比、截面边长、长细比和荷载偏心率等因素对三面火灾作用下带保护层方钢管混凝土的耐火极限的影响。结果表明:保护层厚度、荷载比、截面边长、长细比、荷载偏心率(当荷载偏向于背火面时)是三面火灾作用下影响方钢管混凝土柱耐火性能的主要因素。确定了满足现行规范要求的不同耐火等级的三面火灾作用下方钢管混凝土柱需要的厚涂型防火保护层最小厚度,以供抗火设计参考。

CFST columns may be exposed to three-side fire when they are subjected to an actual fire. The decrease of fire exposure boundaries leads to generally lower cross-sectional temperature, thus inducing an unsymmetrical temperature distribution and additional load eccentricity, which causes fire resistance behaviors differing from fourside fire condition. A series of parametric analysis was carried out for the fire resistance of the columns in three-side fire, in which thickness of fire proof coating, load ratio, cross sectional depth, slenderness ratio and load eccentricity ratio were taken into account. The analysis results indicate that the load ratio, sectional width and slenderness ratio are the main parameters that influence the fire resistance of concrete filled SHS columns. The influence of the loading eccentricity is also obvious when load location leaning to the unexposed side. Hereafter a set of design tables in which minimum thickness of fire-proof coating may be determined, and the tames may provide references for fire design of those concrete-filled SHS being exposed to three-side fire in construction application.