网格箍筋约束混凝土柱轴压受力性能试验研究

为研究使用网格箍筋强度不同、素混凝土轴心抗压强度不同的约束混凝土的轴压受力性能，完成了39个网格箍筋约束混凝土方柱的轴心受压试验。混凝土设计强度等级为C20、C30、C40、C50，箍筋分别选用HRB335、HRB400、HRB500、HRB600钢筋，体积配箍率范围为1.0%～2.2%。试验结果表明：约束混凝土压应力达到峰值时，受压试件的约束箍筋屈服；随着配箍特征值增大，网格箍筋约束混凝土峰值压应力和峰值压应变提高幅度增大，受压应力-应变曲线下降段变缓。根据试验结果，通过回归分析获得了网格箍筋约束混凝土峰值压应力、峰值压应变的计算公式；建立了相应的轴心受压应力-应变模型，与几种具有代表性的箍筋约束混凝土应力-应变模型的对比表明，建立的模型与试验结果吻合较好；提出了约束混凝土极限压应变计算方法。

EXPERIMENTAL STUDY ON AXIAL COMPRESSION BEHAVIOR OF CONCRETE COLUMNS CONFINED BY GRID STIRRUPS

In order to study the axial compression behavior of the confined concrete with grid stirrups of different strength and plain concrete of different axial compressive strength, the axial compression tests of 39 concrete square columns confined by grid stirrups were completed. The stirrups are made of HRB335, HRB400, HRB500 and HRB600 reinforced bar. The volume stirrup ratio is between 1.0% and 2.2%. The design strength grades of concrete are C20, C30, C40 and C50. The test results show that stirrups yield under the peak stress of confined concrete. With the increase of the stirrup characteristic value, the increasing degree of peak stress and peak strain of the concrete confined by grid stirrups increases and the descending branch of stress-strain curve become flat. According to the test results, formulas for calculating peak stress and peak strain of concrete confined by grid stirrups are obtained. The corresponding axial compression stress-strain model is established. The comparison with several typical stress-strain models of concrete confined by stirrups shows that: the results calculated by the axial compressive stress-strain model are in a good agreement with the test results, thusly another method for calculating the ultimate compressive strain of confined concrete is proposed.