约束钢筋混凝土框架的耐火性能试验研究

Experimental Research on Fire Resistance of Restrained Reinforced Concrete Frames

开展了3榀单层双跨约束钢筋混凝土框架在ISO834标准升温过程下的明火试验,考察了框架的高温反应及其破坏形态,分析了约束钢筋对框架耐火性能的影响。试验结果表明:(1)由于框架梁的高跨比较大,框架在荷载和高温作用下的破坏形态主要表现为框架梁的剪切破坏,破坏区基本集中在加载点与柱顶之间的斜向区域;(2)在框架梁破坏的最后时刻,由于其跨中挠度急速增大,梁内纵向钢筋将以类似悬链索的形式发挥作用;(3)约束钢筋虽然在升温中、前期对左、右框架边柱顶端之间相对距离的增大效应具有一定抑制作用,但对框架的耐火极限影响不大。

Three specimens of one-storey double-span reinforced concrete frames subjected to ISO-834 fire are tested in this paper. The fire responses and failure modes of the test frames are investigated, and the influence of the restrained steel bars on fire behaviours of the test frames are also studied. Test results show that： （ 1 ） because the height-span ratios of frame beams are large, the main failure mode of the test frames subjected to vertical loading and high temperature is shear failure of frame beam, and the failure zones are mainly located in the slanted region between the loading points and the column upper ends ; （2） at the failure stage of frame beams, the mid-span deflections of beams increased rapidly, the longitudinal steel bars in beams may behavior by catenary action; （3） although the restrained steel bars can inhibit the increasing of the relative displacement between two side-columns to some extent, they have little effect on the fire resistance of frame.