高速铁路双洋大桥预应力孔道摩阻试验研究

Experiment Research on Friction Resistance of Prestressed Duct of Shuangyang Bridge in High-speed Railway

双洋大桥是大跨度铁路连续箱梁桥,孔道摩阻系数的确定是其施工控制中的关键问题,会影响控制张拉力的准确施加.目前桥梁设计规范虽给出了孔道摩阻和偏差系数的取值范围,但是预应力孔道摩阻影响因素复杂,需要通过现场摩阻试验才能确定.选择主桥5号墩顶1号块直筋和弯筋2种典型测试钢束,通过在垫板和限位板之间设置高精度穿心式压力传感器,千斤顶后工具锚设置夹片的安装方法,开展了双洋大桥孔道摩阻试验研究,并采用最小二乘法计算了预应力束孔道摩阻系数.试验表明:该桥孔道摩阻系数μ为0.232,孔道偏差系数k为0.002 6,均大于设计推荐值;弯曲型预应力钢束摩阻偏差大于直线型钢束,且钢束长度越大,偏差值越大,孔道摩阻损失不容忽视.

The Shuangyang Bridge is a continuous beam bridge with large span; it is important to determine duct friction coefficients in construction, which affect the accuracy of the design and control of tensile force. At present, the ranges of friction resistance coefficient and deviation coefficient have been given in the bridge design code. However, the influence factors of the frictional resistance of prestressed ducts are complex, which needed to be determined through the field test. The straight and curved steel strands were selected in the block # 1 at the top of pier #5 ; the duct friction test of Shuangyang Bridge was processed by setting high precision through-type pressure sensor between the backing plate and the location-limited plate and clamping jaws with wedges were behind jacks. The least square method is used to calculate the friction coefficient of the prestressed duct. The experimental results show that the friction resistance coefficient of the duct is 0. 232 and deviation coefficient of duct is 0. 0026, both of which are bigger than recommended values in code; the friction resistance of the curved prestressed steel strands is larger than that of the straight stands is, the larger the length of the steel stands the bigger the deviation value is; and the duct resistance loss cannot be ignored.