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为考察纵筋、箍筋、碳纤维(CFRP)包裹层数、尺寸效应及预设损伤对CFRP约束钢筋混凝土方柱单轴受压应力-应变关系的影响,对边长305mm、高915mm及边长204mm、高612mm共22个CFRP约束钢筋混凝土方柱模型试件进行了单轴受压试验。结果表明:纵筋对应力-应变曲线上的峰值点应力有一定影响,而箍筋对应力-应变曲线形状和应力-应变曲线上的极限点应变均有很大影响,其对应力-应变模型的影响不可忽略;CFRP约束后明显改善了方柱延性,但对峰值点应力提高幅度不大,试验曲线大多存在软化段,为中等约束情况;尺寸效应对CFRP的约束作用有明显影响,已有基于约束比的强弱约束划分对本文试验结果不再适用;预设损伤对应力-应变曲线影响不大,损伤水平较大时峰值点应力和极限点应变稍有降低。提出了可考虑箍筋、CFRP及尺寸效应影响的修正约束比,建议了CFRP约束钢筋混凝土方柱强、中等及弱约束的界定标准,在此基础上建立了CFRP中等约束钢筋混凝土方柱的单轴受压应力-应变模型,模型预测结果与试验结果吻合较好。
In order to investigate the effect of longitudinal reinforcement, stirrup, CFRP number and size on the uniaxial compressive stress-strain relationship of CFRP-confined reinforced concrete square columns, 204mm, 612mm high a total of 22 CFRP-constrained reinforced concrete square column specimens subjected to uniaxial compression test. The results show that the longitudinal reinforcement has some influence on the peak stress of the stress-strain curve, while the stirrup has a great influence on the stress-strain curve and the ultimate strain on the stress-strain curve. The stress-strain model The effect of CFRP can not be neglected. After the restraint of CFRP, the ductility of the square column is obviously improved, but the stress increase of the peak point is not large. Most of the test curves have the softening section, which is moderately restrained. The size effect has a significant effect on the restraint of CFRP, Based on constraint ratio, the constraint of strength and weakness is no longer suitable for the test results in this paper. The preset damage has little effect on the stress-strain curve, and the stress at the peak point and the strain at the limit point slightly decrease when the damage level is large. A modified constraint ratio considering the influence of stirrups, CFRP and size effect is proposed. The criteria for the determination of strong, medium and weak constraints of CFRP-confined reinforced concrete square columns are proposed. Based on this, the uniaxial Compressive stress - strain model, the model predictions and experimental results agree well.