高温下钢筋混凝土异形柱空间框架的试验研究

Experimental Study on RC Space Frames with Specially-Shaped Columns Subjected to Elevated Temperature

开展了3榀足尺钢筋混凝土异形柱空间框架在ISO834标准升温过程下的明火试验,考察了荷载水平和梁柱刚度比对框架破坏形态、关键部位变形历程以及耐火极限的影响.试验结果表明:破坏阶段框架梁呈现出类似悬链索的受力形态;框架节点不同方向水平线位移和该方向相邻框架梁的轴向膨胀量密切相关;框架梁不变、梁柱刚度比增大时,在升温中、后期异形柱空间框架的节点转角呈现更为明显的减小甚至反向趋势;较大的荷载水平会使框架更容易达到其耐火极限,但梁柱刚度比却对框架耐火极限影响不大.研究表明,从结构层次进行抗火研究可以更全面地把握结构及其各组成部分的火灾行为.

Three full-scale reinforced concrete space frames with specially-shaped columns were tested following the ISO834 standard heating process, and the influences of loading level and beam-to-column stiffness ratio on the failure mode, displacement-time curve and fire resistance of the specimens were investigated. Experimental results show that （1） the frame beams in the failure stage reveal a force pattern similar to catenary action; （2） the horizontal linear displacement of the frame joints in different directions are closely related to the axial expansion of the adjacent frame beam in the same direction; （3） when the frame beam keeps unchanged, the rotation of beam-tocolumn joints obviously decreases and even becomes opposite with the increase of column stiffness ratio in the middle and later stages of the test ; and （4） high loading levels make the specimen reach its fire resistance more easily, but the beam-to-column stiffness ratio has no obvious ,effect on fire resistance. It is thus concluded that the research on the fire resistance of a total structure is more convenient to the investigation of fire performance of the structure and its components.