基于无应力长度目标的平行钢绞线斜拉索张拉方法

Tension Strategy Derived by Non-stress Length of Parallel Steel Strand Stay Cables

为改善斜拉桥平行钢绞线拉索以索力控制张拉时需多次重复张拉的复杂操作工序,并减少由此产生的累计误差,同时使得张拉完成后每股钢绞线拉力分布更均匀,选择以钢绞线的无应力长度作为控制张拉的对象,设计了以无应力长度控制钢绞线逐根一次张拉到位的施工方案,并对其进行优化。考虑拉索的几何非线性,建立单根钢绞线的几何状态方程,确定其在目标索力下控制张拉的无应力长度;在实际施工中以该无应力长度控制张拉单根钢绞线,运用分阶段局部寻优的数值方法,考虑实际施工误差和塔、梁变形等因素,对实际施工索力与设计目标索力之间存在的误差进行修正,寻求对应实际工况的控制张拉无应力长度,以实现一次张拉到位、张拉完成后每根钢绞线拉力相等且成桥索力也更精确的目的;最后,通过计算机仿真算例模拟实际工况进行验证。结果表明:对给定的设计成桥目标索力,采用无应力长度控制张拉方案可一次张拉到位,考虑施工误差进行优化后控制张拉的无应力长度与对应实际工况的无应力长度相差较小,经过二次优化后,施工张拉索力与设计目标索力的相对误差为0.72%,且张拉完成后每根钢绞线拉力相等,满足施工要求;相关计算程序经固化后嵌入智能千斤顶可用于斜拉索张拉施工。

In order to improve the complex operation procedures of which the parallel steel strand stay cables of bridges need multiple times tension by taking the tensile cable force to control tension,and reduce the accumulative errors during the process,meanwhile make the forces of the steel strand stay cables be well distributed after the tension.Non-stress length of stay cables,was calculated and chosen to control tension,and construction scheme by the method of once tensioning for every strand was designed,elaborated and optimized.The equation of the stay cable was derived by considering the geometric nonlinearity of the steel strand and the non-stress length controlling tension under target cable forces was obtained.The deviation between designed target cable forces and forces in actual construction phases was amended by using binding methodof hierarchical local optimization,considering artificial errors or deformation of the suspended tower and the girder,adopting the obtained non-stress length to control the tension of the stay cable in actual construction phase.The non-stress length of the steel strand conformed with actual operation can be obtained to achieve the aim of once tensioning and equal pulling force of every steel strand after tension,and more precise cable force of bridges.In the end,a simulation example of actual working conditions was provided to verify the construction scheme.The results show that the given target forces can be finished by once tensioning adopting non-stress length to control the tension scheme.Considering the small deviation between non-stress length of controlling tension after the optimization of artificial errors and non-stress length in actual working conditions,the corresponding error of the tensile cable force decreases to 0.72% after the further optimization.The forces of the steel strand stay cables are equal after the tension,which meets the requirements of construction.The relevant firmware embedded intelligent jack after curing can be used in construction of the steel strand stay cables.