螺旋箍筋约束高强混凝土柱轴心受压性能试验研究

Experimental Study on Axial Compression Behavior of High-strength Concrete Columns Confined by Spiral Stirrups

为探究螺旋箍筋约束高强混凝土柱的轴心受压性能,开展了42根螺旋箍筋约束高强混凝土圆柱的轴压试验,研究了混凝土标准立方体抗压强度(58.0~90.6 MPa)、箍筋屈服强度(480~1219 MPa)、体积配箍率(1.00%~1.60%)与箍筋间距(45~80 mm)对螺旋箍筋约束混凝土柱受压承载力和变形能力的影响。试验结果表明:箍筋约束混凝土在达到峰值压应力时,约束箍筋可能达不到屈服;约束箍筋的强度和体积配箍率相同时,随着高强混凝土强度的增高,约束混凝土达到峰值压应力时箍筋的拉应变减小;混凝土轴心抗压强度、箍筋屈服强度相同时,随着体积配箍率的提高,约束混凝土峰值压应变增大,相应的横向应变也随之增大,箍筋拉应变也增大。基于试验结果,考察了峰值压应力下箍筋拉应变与体积配箍率、混凝土强度、箍筋屈服强度和箍筋间距之间的关系,建立了峰值压应力下约束箍筋拉应变计算公式。拟合得到了约束混凝土峰值压应力f_(cc)、峰值压应变ε_(cc)、下降段曲线的特征参数(峰值压应力后85%峰值应力下的轴向压应变ε_(c85)、50%峰值压应力的轴向压应变ε_(c50))的计算公式。给出了考虑体积配箍率、混凝土轴心抗压强度、箍筋间距和箍筋屈服强度影响的箍筋约束高强混凝土的轴心受压应力-应变关系模型。

The effects of concrete standard cube compressive strength(58.0-90.6 MPa),stirrup yield strength(480-1219 MPa),stirrup volume ratio(1.00%-1.60%),and stirrup spacing(45-80 mm)on the bearing capacity and deformation capacity of high-strength concrete columns confined by spiral stirrups were studied through axial compression tests of 42 column specimens.The test results show that the confining stirrups may not yield when the confined concrete reaches the peak compressive stress.When the yield strength and volume ratio of the stirrups remain the same,the tensile strain in the stirrups decreases with increasing concrete strength as the confined concrete reaches the peak compressive stress.When the axial compressive strength of the unconfined concrete and the yield strength of the stirrups remain the same,an increase in the stirrup volume ratio causes increases in the peak compressive strain in the confined concrete,the corresponding transverse strain,and the tensile strain in the stirrups.The test results were then analyzed to determine the relationship between the stirrup tensile strain,stirrup volume ratio,concrete strength,stirrup yield strength,and stirrup spacing under peak compressive stress to establish a formula for the stirrup tensile strain.The formulas for the peak compressive stress,peak compressive strain,and characteristic parameters(axial compressive strain at 85%peak stress following peak compressive stress and axial compressive strain at 50%peak compressive stress following peak compressive stress)of the confined concrete were obtained by fitting.The stress-strain relationship of high-strength concrete columns confined with stirrups was finally derived considering the influence of the stirrup volume ratio,concrete axial compressive strength,stirrup spacing,and stirrup yield strength.