圆钢管钢纤维活性粉末混凝土短柱轴压性能试验研究

Experimental study on mechanical behavior of RPC-filled circular steel tube columns under axial compression

为研究圆钢管钢纤维活性粉末混凝土(RPC)短柱的轴压性能,完成了7根外径219～273 mm的圆钢管钢纤维RPC短柱轴压性能试验,分析了套箍系数、径厚比对轴压试件荷载-应变曲线和破坏特征的影响。结果表明:套箍系数ξ在0.63～0.88时,荷载-位移曲线在峰值荷载后出现下降段,短柱呈现剪切破坏模式;当ξ≥1时,在到达峰值荷载后,荷载下降幅度明显减小或出现回升趋势,短柱呈现腰鼓形破坏模式。在达到峰值荷载的85%之前,试件处于弹性阶段,钢管纵向应变大于横向应变;弹塑性阶段,钢管横向应变增加较快,其横向变形系数超过钢管的泊松比并逐渐增大,钢管对RPC的约束作用不断增强。随着混凝土抗压强度提高,其横向变形系数减小,钢管对核心区RPC约束效果降低。

In order to investigate the axial compression behavior of reactive powder concrete(RPC) filled circular steel tube columns, seven tests on the column specimens that diameter ranged from 219 to 273 mm under axial compression were conducted.The effect of the confinement factor and diameter-thickness ratio on load-strain curves and failure patterns were studied. The experimental results show that the specimens have an obvious descending branch after the peak load and shear failure occurs when the confinement factor ξ ranges from 0.63 to 0.88. The specimens with a confinement factor ξ≥1 exhibit local buckling failure. Moreover, the axial bearing capacity decreases slightly and then gradually regains after the peak load. Before 85% of ultimate load, the longitudinal strain develops faster than the transverse strain in the elastic stage. In the inelastic stage, the transverse strain increases significantly. The transverse stress of steel increases rapidly and the confining force increases because the transverse deformation coefficient of the core RPC exceeds the Poisson’s ratio of the steel tube. With an increase in the concrete compressive strength, the lateral deformation coefficient is decreased, which reduces the confinement effect to the core concrete.