现行铁路桥规中预应力钢筋锚固损失计算方法的改进

Improvement on Computing Method for Anchorage Loss of Prestressed Tendon in Current Railway Bridge Code

在推导现行铁路桥梁设计规范中预应力钢筋有效预应力计算公式的基础上,分析现行铁路桥梁设计规范中预应力钢筋反向摩阻计算公式与摩阻损失计算公式间的不协调和应用时的缺点,给出预应力钢筋锚固损失的实用简化计算公式。从预应力钢筋微段的平衡条件出发,考虑预应力钢筋的变形协调及应力连续条件,建立预应力钢筋锚固损失的精确计算公式,揭示预应力钢筋张拉时摩阻作用与锚固时反摩阻作用的差异,对完善现行铁路桥梁设计规范中的反向摩阻计算方法提出改进建议。研究结果表明:反摩阻作用小于摩阻作用;为了提高计算精度,可将按现行铁路桥梁设计规范计算的锚固损失结果乘以小于1的修正系数,并考虑预应力钢筋实际线型的影响。

On the basis of derivation of the calculation formulas of effective prestress of prestressed tendon in China’s current railway bridge code(CCRBC),the paper analyzed the incompatibility between the formulas of reverse-friction and friction loss of prestressed tendon in the design code and their shortcomings in application.Practical and simplified formulas for calculating anchorage loss of prestressed tendon were provided for the purpose of application.Based on the equilibrium condition of micro segment of prestressed tendon,considering the conditions of deformation compatibility and stress continuity,the precise formulas to calculate the anchorage loss of prestressed tendon were established.The difference between the friction effect of the prestressed tendon during tensioning and the reverse-friction effect of the prestressed tendon during anchoring was revealed.Suggestions for improving the reverse-friction calculation method in CCRBC were presented.The research results show that the reverse-friction effect is smaller than the friction effect.In order to improve the calculation accuracy,the calculated values of anchorage loss by applying the method in CCRBC can be multiplied by a modification factor smaller than 1,and the influences of the actual line shape of prestressed tendon should be considered as well.