高强钢棒螺旋箍筋约束混凝土圆形截面柱受力性能试验研究

为研究高强钢棒螺旋箍筋约束混凝土柱的受力性能，设计了32个约束混凝土柱，对其进行轴心受压试验。试件主要设计参数包括混凝土强度等级为C50、C60、C70、C80，高强钢棒抗拉强度标准值为800、970MPa，体积配箍率为0.9%、1.2%、1.6%、2.0%。试验结果表明：约束混凝土柱在轴向荷载作用下呈腰鼓形破坏或单折剪切破坏，对于确定的非约束混凝土抗压强度和箍筋抗拉强度，约束箍筋体积配箍率较小时发生单折剪切破坏，体积配箍率较大时发生腰鼓形破坏；约束箍筋拉应变随混凝土弹性模量与非约束混凝土抗压强度比值增大而增大，随箍筋体积配箍率增大而减小；约束混凝土柱的体积配箍率大于某一量值时，会出现约束混凝土达到抗压强度时箍筋拉应变小于其屈服应变的情况。基于试验结果，建立了用于判别腰鼓形破坏和单折剪切形破坏的界限，并给出了相应的计算式；建立了约束混凝土柱发生轴压破坏时约束箍筋拉应变计算公式及箍筋受拉屈服对应的最大体积配箍率计算公式，为合理设计高强钢棒螺旋箍筋约束混凝土圆形截面柱提供参考。

Experimental study on mechanical behavior of circular concrete columns confined by high-strength spiral stirrups

In order to observe the mechanical behavior of concrete columns confined by high-strength spiral stirrups, concentric compression test on 32 confined concrete columns was completed. The main test parameters were concrete grades (C50, C60, C70, and C80), standard tensile strength of high-strength steel bars (800 MPa and 970 MPa), and volumetric ratio (0.9%, 1.2%, 1.6%, and 2.0%). The experimental results show that the confined concrete columns exhibit drum-shaped or single-folded shear failure modes under concentric compression. With fixed unconfined concrete compressive strength and stirrup tensile strength, the specimens with lower stirrup volumetric ratios undergo single-folded shear failure while the specimens with higher stirrup volumetric ratios fail in a drum-shaped manner. The stirrup strain increases with an increase in the ratio of the concrete elastic modulus to the unconfined concrete compressive strength, and decreases with an increase in the volumetric ratio. when the volumetric ratio of the confined concrete columns exceeds a certain value, the stirrup can not reach its yield strain even when the ultimate strength of the concrete columns has been achieved. Based on the test results, the boundary values of the two failure shapes are established and the corresponding calculating formula is provided. In addition, a formula for calculating the stirrup strain upon failure of the confined concrete columns under concentric compression, and a formula for calculating the maximum volumetric ratio to ensure stirrup yield, are established. The current study can provides a reference for reasonable design of circular concrete columns confined by high-strength spiral stirrups.