考虑海洋环境钢筋锈蚀的混凝土轴压柱受火性能试验研究

Experimental research on fire resistance performance for RC columns under axial compression with rebar corrosion damages caused by marine environment

为研究受海洋环境钢筋锈蚀后混凝土柱的抗火性能,设计了5根足尺寸钢筋混凝土轴压柱进行试验。采用通电加速氯离子迁移的方式使混凝土柱锈胀开裂以模拟海洋环境损伤,以锈胀裂缝宽度作为损伤指标,控制通电时间使各柱锈胀裂缝宽度分别达到0.05,0.10,0.15,0.20 mm,并对各柱进行使用荷载下的四面受火试验。试验研究表明:在轴压比不变(本文中为0.2)的情况下,柱的裂缝宽度越大,其极限耐火时间越短;裂缝对试件截面经历的最高温度基本无影响;假定等温线与等温线间距正比例分布,基于此假设,对锈蚀钢筋混凝土柱高温下的轴心受压承载力进行计算,计算结果与试验实测值基本一致。

In order to study the fire resistance performance of reinforced concrete( RC) columns with damages caused by marine environment,five full-scale RC columns under axial loading were selected as the research objects and the concrete crack width was defined as the damage index. The accelerated chloride ion migration tests with different energized time were carried out to simulate marine environment,which can rescult in different initial crack width range from 0. 05 mm to 0. 20 mm in the surface of RC columns. The experimental results show that the fire resistance time of the specimen with lager crack width is much shorter than that of less crack width at the same axial compression ratio;concrete crack width even has less influence on the highest temperature of the cross-section. Based on the assumption that section temperature is linearly distributed between the isotherms,a simplified calculation formula taking into account the marine environment for RC columns' bearing capacity under fire was put forward,the calculated results matched the experimental data very well.