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

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.