后张法预应力混凝土梁曲线钢束锚固损失的精确分析

为了改进后张梁曲线钢束锚固损失计算方法，通过分析钢束微段的平衡，利用变形协调条件及应力连续条件，导出了后张梁曲线钢束锚固损失的精确计算公式。在导出的精确公式的基础上，分析了钢束张拉时的摩阻作用与锚固时的反摩阻作用之间的差别，指出了现行桥梁设计规范中锚固损失计算方法的近似性和不合理性。通过简支梁和连续梁钢束算例，对比了现行桥梁设计规范中的锚固损失计算方法及误差。研究结果表明：钢束锚固时的反摩阻作用小于张拉时的摩阻作用；现行铁路桥梁设计规范中的简化计算方法具有较好的计算精度，而现行公路桥梁设计规范中的简化计算方法会导致很大偏差；按现行公路桥梁设计规范中给出的简化公式计算的反摩阻影响长度可超过精确值70%以上，钢束端部的锚固损失计算值小于精确值30%以上；从简化计算考虑，建议设计公路桥梁时采用现行铁路桥梁设计规范中的反向摩阻计算方法。

Exact Analysis on Anchorage Loss of Curved Tendon in Post-tensioned Prestressed Concrete Beams

In order to improve the calculation method for anchorage loss of curved tendon in post-tensioned beams, the precise formulas for calculating anchorage loss of curved tendon in post-tensioned beams were derived by analyzing the equilibrium of a differential segment tendon and using the conditions of deformation compatibility and stress continuity. Based on the precise formulas derived, the difference between the friction effect in stretching and the reverse-friction effect in anchoring was analyzed. The approximation and irrationality of the anchorage loss calculation method in current bridge design codes were presented. Numerical examples of tendons in a simply supported beam and a continuous beam were provided to compare the calculation methods and errors for anchorage loss in the current bridge design codes. The results show that the reverse-friction effect in anchoring is smaller than the friction effect in stretching, and that the simplified method in current railway bridge code has relatively good precision while that in current highway bridge code may result in large deviation. Moreover, the reverse-friction influence length calculated by applying the current highway bridge code exceeds the precise value more than 70%, and the calculated anchorage loss at the ends of tendon underestimates precise value more than 30%. Therefore, in consideration of simplification, it is suggested that the reverse-friction analysis method in the current railway bridge design code can be applied in the design of highway bridges.