钢管混凝土柱低温轴压性能研究

Studies on axial compression behaviors of concrete-filled steel tubular columns at low temperature

为研究应用于寒区工程结构的普通及高强钢管混凝土柱的轴压性能,对15个采用普通及高强钢管混凝土柱开展低温轴压试验,研究其在低温环境下的轴压破坏形态、荷载-位移曲线、荷载-应变曲线、受压承载力、初始刚度及位移延性系数等性能指标,分析低温水平(20、-30、-60、-80℃)、钢材强度(Q235、Q690、Q960)对组合柱轴压性能影响。结果表明:-30~-80℃低温环境下,组合柱破坏形态为钢管端部或腰部鼓曲、角部焊缝撕裂及核心混凝土压碎等。低温下组合柱的荷载-位移曲线与常温下的相似,包括弹性、非线性段以及峰值荷载后的退化段。低温水平对组合柱受压承载力及初始刚度均有提高,但削弱其延性。随着钢管材料强度增大,钢管混凝土柱低温下轴压性能有所改善。最后,通过对我国现行GB 50936—2014和新加坡BC 4-2015中钢管混凝土柱受压承载力计算方法进行对比分析,结果表明,GB 50936—2014承载力设计公式偏于不安全因素较大,规范BC 4-2015较为保守。

The axial compressive behavior of concrete-filled mild/high-strength steel tubular composite columns under low temperature was investigated,which was developed for the arctic engineering infrastructures.Axial compression tests on totally 15 concrete-filled mild/high-strength steel tubular composite columns were carried out.The mechanical behaviors of these composite columns were revealed,including failure mode,load-shortening curves,load-strain curves,ultimate compression capacity,and ductility ratios etc.The influences of low temperatures(20,-30,-60,-80℃)and strength of steel(Q235,Q690,Q960)on compression behavior were analyzed.Test results indicate that failure modes from-30℃to-80℃,e.g.,local buckling of steel tube,weld fracture at the corner of steel tube,and concrete crushing,are observed.The load-shortening behaviors of these composite columns at both ambient and low temperatures are close,which include elastic,nonlinear,and recession stages.Low temperatures improve the ultimate compression capacity and stiffness of the columns,but compromise their ductility.Increasing the strength of steel tube improves the low-temperature compressive behavior of the columns.Finally,the prediction methods of ultimate compressive resistance of current codes are compared and analyzed,and the validations against test results show that the design formula of bearing capacity in the GB 50936—2014 is unsafe,and the code BC 4 is conservative.