SRPE套管约束混凝土短柱轴压性能试验

针对西部盐渍土地区钢筋混凝土桥梁墩柱的腐蚀问题,提出一种新型组合结构“钢骨架聚乙烯塑料复合材料(SRPE)套管约束混凝土柱”,该新型组合结构能够彻底隔离墩柱与各种腐蚀性离子的接触。为研究其轴心受压力学性能,对12个SRPE套管约束混凝土短柱试件及3个素混凝土短柱试件进行了轴心受压试验,分析了混凝土强度等级、SRPE套管环向约束应力和膨胀剂对试件的破坏形态、荷载-位移曲线、延性和初始压缩刚度的影响规律。根据SRPE套管环向约束应力计算方法和约束混凝土短柱抗压强度计算公式,建立了SRPE套管约束混凝土短柱轴心抗压强度计算方法。结果表明:SRPE套管约束混凝土短柱的最终破坏形态均为核心混凝土发生斜剪破坏,且随着SRPE套管环向约束应力的增高,试件的剪斜变形角逐渐减小; 试件混凝土强度等级越高,其荷载-位移曲线的峰值荷载越大,下降段更陡峭,试件的脆性越大; SRPE套管能够明显提高试件的承载力、峰值变形及延性,且随着SRPE套管环向约束应力的增大,试件各项力学性能均呈逐渐上升趋势; 提高混凝土强度等级,试件的承载力提高,但峰值变形和延性有所降低; 掺入膨胀剂(质量分数10%)使试件的承载力降低,而峰值变形、初始压缩刚度及延性则稍有提高; 所建立的轴心抗压承载力计算方法可为工程实践提供参考。

Experiment on Performance of SRPE Pipe Confined Concrete Circular Stub Columns Under Axial Compression

In order to solve the corrosion problem of reinforced concrete bridge piers and columns in saline soil area of Western China, a new type of composite structure “steel reinforced polyethylene plastic(SRPE)pipes casing confined concrete column” was proposed, which could completely isolate the pier from various corrosive ions. In order to study its axial compression performance, 12 specimens of SRPE pipe concrete stub columns and 3 specimens of plain concrete stub columns were tested under axial compression, and the influence of concrete strength grade, circumferential constrained stress and expansive agent on the failure form, load-displacement curve, ductility and initial stiffness of the specimens were analyzed. According to the calculation method of circumferential constrained stress of SRPE pipe and the calculation formula of compressive strength of confined concrete stub columns, the calculation method of axial compressive bearing capacity of SRPE pipe concrete stub columns was established. The results show that the ultimate failure mode of SRPE pipe confined concrete stub column is inclined shear failure of core concrete, and with the increase of SRPE pipe circumferential restraint stress, the shear deflection angle of the specimen decreases gradually; the higher the concrete strength grade of the specimens, the greater the peak load of load-displacement curve, the steeper the descending section, and the greater the brittleness of the specimens. SRPE pipe can significantly improve the bearing capacity, peak deformation, initial compression stiffness and ductility of the specimens, and with the increase of circumferential restraint stress of the SRPE pipe, the mechanical properties of the specimens show a trend of gradual increase. With the increase of concrete strength grade, the bearing capacity of specimens increases, but the peak deformation and ductility decrease. The addition of expansive agent(mass fraction of 10%)only reduces the bearing capacity of the specimen, but improves the peak deformation, initial compression stiffness and ductility of the specimen to some extent. The calculation method of axial compressive bearing capacity of pipe concrete short columns can provide reference for engineering practice.