加强型预应力混凝土管桩抗弯剪性能试验研究

摘要

为有效解决普通预应力混凝土管桩抗弯(剪)性能较差的现状,研发了主筋加强型预应力混凝土管桩,并进行抗弯及抗剪性能方面的原型试验研究.抗弯试验结果显示:非预应力螺纹钢筋的配置较大幅度提高了预应力混凝土管桩的抗弯性能,且原有预应力钢筋配筋率越低效果越明显,但抗裂性能没有明显改善;螺纹钢筋的配置明显减小了桩身裂缝的长度和平均宽度,裂缝分布范围及数量有一定程度的增加.2种类型管桩的主要应力均位于跨中纯弯段内,裂缝出现以前跨中界面应变基本符合平截面假定,裂缝出现后中性轴上移.抗剪试验显示:非预应力螺纹钢筋的配置改变了桩身的应力和裂缝分布规律,较大幅度减小了管桩在剪力作用下的变形量,但抗剪承载力提高程度取决于原有预应力钢筋配筋率.对比试验结果说明此创新型管桩在抗弯及抗剪性能方面的优势是明显的.%The flexural and shearing properties of innovatively invented reinforced prestressed concrete pipe pile were researched by a comprehensive field test program to improve the flexural and shearing properties of the conventional prestressed concrete pipe pile (PHC) pile. The test results show that the allocation of nonprestressed rolling rebar evidently improves the flexural properties except the cracking resistant, and a larger reinforcement ratio of prestressed steel bar leads to a greater improvement. The new technology also decreases the length and average width of concrete cracks, whereas expands their distribution to some extent. The stresses of both type piles concentrate on the pure bending section. The strain of mid-span cross section accords with the hypothesis of planar section until the concrete cracks and the neutral axis moves higher correspondingly. The shearing test results show that the allocation of nonprestressed rolling rebar changes the distribution of stress and cracks and decreases the deformation, and the extent of shearing capacity improvement depends on the reinforcement ratio of prestressed steel bar. The results of the comparative tests show the excellent flexural and shearing properties for this new type pile.