试验方法对锈蚀钢筋混凝土黏结性能影响的数值模拟研究

Numerical simulation study on the influence of experimental methods on the bond performance between corroded rebars and concrete

关键词:  试验方式  梁模型  拉拔模型  破坏模式  黏结应力滑移曲线  数值模拟

Key words:  experimental method  beam model  pull-out model  failure mode  bond stress-slip curve  numerical simulation

摘要:

为探究不同试验方法对锈蚀钢筋与混凝土黏结性能的影响,对拉拔试验和梁式试验开展数值模拟研究,分别建立对应的拉拔模型和梁模型,分析受拉钢筋非均匀锈蚀和约束条件（厚径比和箍筋约束情况）对黏结性能的影响。在数值模型中,通过对受拉筋及其周围混凝土的精细化建模来模拟机械咬合力,通过面面接触来反映摩擦力,忽略化学胶结力,考虑到受拉钢筋横截面的锈蚀非均质性,采用两阶段数值分析方法,即先通过施加强制位移模拟锈蚀对钢筋混凝土界面的影响,然后再分析锈蚀试件的黏结性能。研究表明:试验方法对锈蚀试件的破坏模式和黏结应力滑移曲线有显著影响。梁模型和拉拔模型在发生黏结破坏时均会加深和加宽原有锈胀裂缝,但梁模型还会产生贯穿黏结区的斜向裂缝；拉拔模型的黏结强度和下降段斜率明显大于梁模型；箍筋约束情况对梁模型和拉拔模型黏结强度的影响差别不大,而厚径比由2.0增加到3.5,3%锈蚀率时梁模型和拉拔模型黏结强度分别增加了16%和32%。通过与试验结果对比证明了上述数值模型的合理性,并进一步建立了不同试验方式下黏结强度归一化模型。黏结强度归一化模型计算结果与数值模拟结果吻合较好,验证了所提出归一化模型的可靠性。

Abstract:

To investigate the influence of different experimental methods on the bond performance between corroded rebars and concrete, numerical simulations were conducted on pull-out tests and beam tests. Corresponding pull-out and beam models were established, and the effects of non-uniform corrosion of tensile rebars and confinement conditions (thickness-diameter ratio and stirrup confinement) on bond performance were analyzed. In the numerical models, mechanical interlocking forces were simulated by fine modeling of the tensile rebar and the surrounding concrete, while frictional forces were reflected through face-to-face contact ignoring chemical bond forces. The corrosion heterogeneity within the cross-section of tensile rebar was also considered. A two-stage numerical analysis method was adopted, in which the influence of corrosion on the bond behavior between the rebars and the concrete interface was simulated by applying enforced displacements and then the bond performance of corroded specimens was analyzed. The results show that the experimental methods have a significant impact on the failure mode and bond stress-slip curve of the corroded specimens. The existing corrosion-induced cracks are deepened and widened in both the beam and pull-out models when the bond failure occurs, but the beam model also generates diagonally traversing cracks throughout the bond area. The bond strength and descending segment slope in the pull-out model are significantly greater than those in the beam model. Stirrups barely influence the bond strength. As the thickness-diameter ratio increases from 2.0 to 3.5, the bond strength in the beam model and pull-out model increases by 16% and 32% respectively at 3% corrosion rate. After demonstrating the validity of the aforementioned numerical model through comparing numerical results with experimental results, a normalized model was established for bond strength applicable to different test methods. Subsequently, comparison between the results calculated by this normalized bond strength model and those obtained from numerical simulations reveals good agreement, thereby confirming the reliability of the proposed normalized model.