钢管约束的钢管混凝土轴压短柱长期变形性能

Deformation behavior of steel tube-confined concrete-filled steel tube columns under sustained axial compression

摘要:

为分析钢管约束的钢管混凝土柱在长期荷载作用下的变形性能,进行了16个钢管约束的钢管混凝土短柱和2个钢管混凝土短柱的长期持荷试验,持荷时间为350 d。主要研究参数核心混凝土应力比为0.35、0.50和0.65,双层钢管总含钢率为5.8%、10.5%和15.0%,内层钢管与外层钢管含钢率比值为0.30、1.25和2.23。基于素混凝土的长期变形理论计算模型,通过分析施加纵向长期荷载时构件的受力机理,推导出适用于钢管约束的钢管混凝土轴压短柱长期变形的理论计算方法。试验结果表明:长期变形随核心混凝土应力比的提高而增大,随总含钢率、内层与外层钢管含钢率比值的增大而减小。理论计算曲线与试验数据曲线的对比和分析表明:长期变形随相对湿度的减小而增大,采用不同混凝土收缩徐变模型时,相对湿度的影响程度不同,其中CEB-FIP 2010模型的吻合效果最好。建议采用CEB-FIP 2010模型并取相对湿度为100%来计算钢管约束的钢管混凝土柱的长期变形。

Abstract:

Long-term tests under axial compression were carried out on 16 steel tube-confined concrete-filled steel tube columns and two concrete-filled steel tube columns for 350 d to investigate the long-term deformation performance. The main research parameters were stress ratio of the core concrete (0.5,0.50, and 0.65), total steel ratio of the inner and outer steel tubes (5.8%, 10.5%, and 15.0%), and the steel ratio between the inner and outer steel tubes (0.0,1.25, and 2.23). The working mechanism of the steel tube-confined concrete-filled steel tube columns under long-term axial compression was analyzed, and a theoretical calculation method for long-term deformation of steel tube-confined concrete-filled steel tube columns was established. Results show that the long-term deformation increased with the increase in the stress ratio of the core concrete, and decreased when the total steel ratio and the ratio between the inner and outer steel tubes increased. The comparison between the theoretical and test results shows that the long-term deformation increased with the decrease in relative humidity. When different concrete shrinkage and creep models were used, the influence of relative humidity varied, and the CEB-FIP 2010 model had the best performance. Therefore, the CEB-FIP 2010 model with 100% relative humidity is recommended for the calculation of steel tube-confined concrete-filled steel tube columns under long-term deformation.