纤维网增强砂浆约束混凝土圆柱的约束机理研究

RESEARCH ON CONFINEMENT MECHANISM OF CONCRETE CYLINDERS CONFINED WITH TEXTILE-REINFORCED MORTAR

  • 摘要: 为研究纤维网增强砂浆(textile reinforced mortar, TRM)加固层对混凝土的约束机理,选用低强度砂浆作为TRM基体,以尽可能排除其轴向承载力对应力-应变行为的影响。对18个混凝土柱试件(包括3根对比柱和15根约束柱)进行轴心压缩试验,分析了试件的破坏形态及应力-应变曲线的特征,并将试验结果与复材约束混凝土经典分析模型的预测值进行了比较。研究结果表明:TRM的约束作用符合典型的被动式约束混凝土特征,约束效应在轴向应变超过素混凝土的峰值应变后被明显激活;TRM约束混凝土的应力-应变行为在约束效应未激活时与素混凝土类似,之后表现为约束效应较弱的快速下降段,但其斜率与未约束混凝土相比明显变缓;当纤维网层数超过2层时,可以克服加载系统刚度的不足,测到高强度混凝土应力-应变曲线的完整下降段;复材约束混凝土分析模型能够准确描述TRM对混凝土的约束效应,特别是约束效应激活段的曲线斜率与试验数据较吻合。

     

    Abstract: To investigate the confinement mechanism of textile-reinforced mortar (TRM) on concrete, low-strength mortar was used as the TRM matrix to minimize the impact of its axial bearing capacity on stress-strain behaviors. Axial compression tests were performed on 18 concrete column specimens, including 3 reference columns and 15 confined columns, to examine their failure modes and the characteristics of the stress-strain curves. The test outcomes were compared with the predictions from a classical analysis-oriented stress-strain model for fiber-reinforced polymer (FRP)-confined concrete. The findings indicate that TRM's confinement effect aligns with the typical passive confinement characteristics observed in concrete, with significant activation of this effect when the axial strain surpasses the peak strain of plain concrete. Before the activation of the confinement effect, the stress-strain behavior of TRM-confined concrete resembles that of plain concrete, which is then followed by a phase of rapid decline with a relatively weaker confinement effect. However, the rate of decline is substantially slower than that of unconfined concrete. Additionally, when more than two textile layers are used, it is possible to overcome the stiffness shortcomings of the loading system, allowing for a complete analysis of the descending portion of the high-strength concrete stress-strain curve. The FRP-confined concrete stress-strain model effectively captures the confinement effect of TRM on concrete, especially in matching the slope of the curve during the confinement activation phase with the experimental data.

     

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