高温后反复荷载下钢-PVA混杂纤维高性能混凝土与变形钢筋黏结性能试验

Experimental of the bond behavior between Steel-PVA hybrid fiber high performance concrete and deformed steel bars under repeated loading after high temperature

  • 摘要: 为研究高温后反复荷载下钢-聚乙烯醇混杂纤维高性能混凝土(Steel-Polyvinyl alcohols Hybrid Fiber High Performance Concrete, S-PVA HFHPC)与变形钢筋的黏结性能,选取钢纤维体积率、PVA纤维体积率、矿粉取代率为正交因素,设计并制作25组试件,历经目标温度200℃、400℃、600℃、800℃后,完成反复荷载作用下的中心拉拔试验,探究不同参数下S-PVA HFHPC与变形钢筋的黏结破坏形态、黏结应力-滑移曲线及黏结强度的变化规律。试验研究表明:高温后的试件均表现为钢筋拔出破坏;黏结应力-滑移曲线整体关于坐标原点中心对称呈反“S”型,曲线中部出现“捏拢”现象;S-PVA混杂纤维对混凝土与钢筋的黏结强度存在正混杂效应,钢纤维对黏结强度的提升更显著,各组试件的黏结强度随历经目标温度的升高呈下降趋势,历经目标温度200℃后,黏结强度的提升最为显著,最大可提高56.11%;S-PVA混杂纤维可显著提升滞回耗能能力,有效抑制加载循环过程中黏结应力与卸载刚度的退化,其中卸载刚度与滞回耗能的最小衰减率分别为28.33%和1.60%;考虑高温后材料强度折减和纤维增强因素,建立高温后反复荷载下S-PVA HFHPC与变形钢筋黏结强度计算公式,为高温后反复荷载耦合工况作用下钢筋S-PVA HFHPC结构的设计和应用提供参考。

     

    Abstract: To study the bond performance between steel-polyvinyl alcohol hybrid fiber high-performance concrete (Steel-Polyvinyl alcohol Hybrid Fiber High Performance Concrete, S-PVA HFHPC) and deformed steel bars under repeated loading after high temperatures, the volume fractions of steel fiber and PVA fiber, as well as the mineral powder replacement rate, were selected as orthogonal factors. Twenty-five groups of specimens were designed and fabricated. After exposure to target temperatures of 200℃, 400℃, 600℃, and 800℃, central pull-out tests under repeated loading were conducted to investigate the bond failure modes, bond stress-slip curves, and variations in bond strength of S-PVA HFHPC with deformed steel bars under different parameters. The experimental study showed that: All specimens after high-temperature exposure exhibited pull-out failure of the steel bars; the bond stress-slip curves were overall symmetric about the origin, displaying an inverted “S” shape, with a “pinching” phenomenon appearing in the middle of the curve; the incorporation of S-PVA hybrid fibers had a positive hybrid effect on the bond strength between concrete and steel bars, with steel fibers showing a more significant increase in bond strength; the bond strength of all specimen groups decreased with increasing target temperature, with the most significant improvement occurring at 200℃, reaching a maximum increase of 56.11%; the incorporation of S-PVA hybrid fibers significantly enhanced hysteretic energy dissipation capability and effectively suppressed the degradation of bond stress and unloading stiffness during repeated loading, with the minimum reduction rates of unloading stiffness and hysteretic energy being 28.33% and 1.60%, respectively; considering the material strength reduction after high temperature and the fiber reinforcement effect, a calculation formula for the bond strength of S-PVA HFHPC with deformed steel bars under repeated loading after high temperatures was established, providing a reference for the design and application of reinforced structures using S-PVA HFHPC under coupled conditions of high temperature and repeated loading.

     

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