复合配筋混凝土预制方桩抗剪性能试验研究

EXPERIMENTAL RESEARCH ON SHEAR BEHAVIOR OF COMPOSITE REINFORCEMENT CONCRETE PREFABRICATED SQUARE PILES

创新研发了复合配筋混凝土预制方桩,通过施加预应力提高桩身的抗裂性能,配置非预应力钢筋增强桩身的抗弯承载力和延性,采用实心而非空心截面且合理配置箍筋提高桩身的抗剪性能。对3种常用规格共9根方桩试件进行足尺度抗剪性能试验,对比研究预应力和非预应力混凝土预制方桩在抗裂性能、抗剪承载力、变形性能及破坏特征等方面的差异。结果表明:施加预应力可显著提高混凝土预制方桩试件斜截面的开裂剪力,限制并延缓桩身裂缝的发展,提高方桩的极限抗剪承载力,降低斜截面抗剪破坏的变形能力;方桩试件的极限抗剪承载力试验值较GB 13476—2009《先张法预应力混凝土管桩》推荐算式的计算值大50%以上;试件破坏形式有两种:斜截面抗剪破坏和正截面抗弯破坏。因此,此新型预制方桩能够有效解决预应力混凝土管桩水平承载力低、普通混凝土预制方桩抗裂性能差的问题。

The composite reinforcement concrete prefabricated square piles were innovatively developed. The anticracking performance of the pile were improved by applying prestress,both of the flexural bearing capacity and the ductility of the pile could be enhanced by increasing non-prestressed reinforcement,and the shear capacity of the pile could be strengthened by adopting solid section instead of hollow section and rational allocation of stirrups. The shear behavior tests of nine full-size square pile specimens for three kinds of common specifications were conducted to identify the differences between prestressed and non-prestressed concrete prefabricated square piles from anti-cracking performance,shear bearing capacity,deformation behavior and failure characteristics. The results showed that the application of prestress could significantly enhance the cracking shear of oblique section,constrain and delay the development of cracks on the pile body,and enhance the ultimate shear bearing capacity,but reduce the deformation capacity of square pile specimens for shear failure. The ultimate shear bearing capacity of square pile specimens were all over 50% greater than the values calculated by the formula from the specification GB 13476—2009. There were two kinds of failure modes for square pile specimens,i. e.,the shear failure of oblique section and the flexural failure of normal section. Therefore,the new type of prefabricated piles could solve the existing problems of the low horizontal bearing capacity of the prestressed concrete pipe piles and the poor anti-cracking performance of conventional concrete prefabricated square piles.