预应力混凝土连续刚构桥中预应力损失试验的张拉与控制

On Tension & Control of Prestressing Loss Test in Prestressed Concrete Continuous Rigid Frame Bridge

在预应力混凝土连续刚构桥中,预应力钢束线型多为空间三维曲线,且竖弯曲率较大,因而预应力摩阻损失较大。基于某库区大跨预应力混凝土连续刚构桥预应力的现场测试结果,对于较长的空间曲线预应力束而言,根据现行规范、公式及参数估算的预应力损失偏小,给结构带来安全隐患。而在预应力损失中,摩阻损失占有很大比重。在预应力损失试验中,预应力筋的张拉应力和伸长值是最重要的两大控制指标,如果控制不当,容易出现张拉应力损失而造成欠张拉或超张拉。为得到准确的预应力损失数据,为优化设计提供数据支持,试验过程中应对预应力筋张拉进行控制。

Most of prestressed tendon linetypes are space 3D curves with large vertical curvature in prestressed concrete continuous rigid frame bridge, therefore, the prestressing friction loss values are relatively larger. According to the site test results of some large-span prestressed concrete continuous rigid frame bridge in a reservoir area, the prestressing loss values are smaller for longer space curve prestressed tendons based on current standards, formulas and parameters estimation, which will bring potential safety risk for the structure. And the friction loss occupies a large proportion of the prestressing loss. In the prestressing loss test, the tension stress & elongation value are the most important controlling indexes, and it will appear insufficient or over tensioning if in the condition of improper control. To obtain accurate stress loss values and to provide data support for optimal design, prestressed tendon tensioning shall be controlled during the test process.