聚丙烯纤维-钢筋/混凝土管节受力性能试验

Experimental study on the mechanical properties of polypropylene fiber-steel bar reinforced concrete pipe

  • 摘要: 顶管施工中钢筋/混凝土管节存在开裂现象,严重影响工程质量与后续营运。鉴于聚丙烯纤维具有改善混凝土抗拉、抗裂性能的作用,本文采用2种聚丙烯细纤维和1种聚丙烯粗纤维,设计了无纤维、单掺粗纤维及混掺三种尺度纤维的3组钢筋/混凝土管试件,进行了三点试验,对比分析管节的开裂破坏形态、荷载挠度曲线和开裂延性指标。并建立纤维混凝土管节三点试验的有限元模型,进一步探究聚丙烯纤维掺量对钢筋/混凝土管节受力性能的影响规律。结果表明,聚丙烯粗纤维可提高混凝土管的抗裂与承载能力,聚丙烯粗、细纤维的协同作用使管达到更高的使用和极限强度。相比无纤维管,混掺多尺度纤维提升管的使用强度和极限强度分别为28.7%和36.4%。此外,数值模拟合理地预测了纤维/混凝土管节的荷载挠度响应,并针对混凝土管节的极限强度值,得到单掺和混掺聚丙烯纤维时粗纤维的最佳掺量。

     

    Abstract: The cracking of reinforced concrete pipe during pipe jacking construction seriously affects the project quality and subsequent operation. In view of the role of polypropylene fiber in improving the crack resistance and tensile properties of concrete, this paper adopted two types of fine polypropylene fibers and one type of crude polypropylene fiber, designing 3 groups of reinforced concrete pipe specimens, which were reinforced with plain concrete, single-scale crude fiber and hybrid three-scale fibers. The three-edge-bearing test was carried out. The cracking failure patterns, load-deflection responses and ductility indexes after cracking of these pipes were comparatively analyzed. A finite element numerical model was developed for reproducing the three-edge-bearing test to investigate the influence law of polypropylene fiber content on the mechanical properties of reinforced concrete pipe. The results show that the crack resistance and load-bearing capacities of concrete pipe are improved by adding crude polypropylene fiber, and the higher service and ultimate strength of pipe are achieved under the synergistic action of fine and crude polypropylene fibers. Compared with the pipe without fiber, the hybrid multi-scale fibers increase the service and ultimate strength by 28.7% and 36.4%. In addition, using this numerical simulation method, the load-deflection responses of fiber reinforced concrete pipe can be reasonably predicted, and the optimum contents of crude fiber when incorporating single-scale and three-scale fibers are obtained, aiming to the higher ultimate strength of concrete pipe.

     

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