现行规范中后张梁锚固损失对比分析

Comparison and Analysis of Anchorage Losses of Post-tensioned Bridge in Current Code

针对现行规范在锚固损失的计算过程中不合理的地方影响后张梁的设计和检算问题,推导出后张梁锚固损失和反摩阻影响长度精确计算公式,通过连续梁悬臂施工算例,对比现行铁路桥规和公路桥规中锚固损失和反摩阻影响长度计算结果与精确值之间的误差,揭示了我国现行设计规范中后张梁预应力钢束锚固损失和反摩阻影响长度计算方法的不合理性;同时研究了梁端直线段与圆弧线交点到梁端水平投影距离、圆弧半径和圆心角对后张梁梁端锚固损失的影响.结果表明:对于梁端直线段和圆弧线交点处的锚固损失,按照铁路桥规计算结果高于精确值5.0%,按照公路桥规计算结果低于精确值36.7%,公路桥规计算结果出现了严重的失真现象,增加梁端直线段与圆弧线交点到梁端水平投影距离、增大圆弧半径和减小圆心角都能减小梁端锚固损失.

In view of the unreasonable place in the calculation process of anchorage loss in the current code,which affects the design and checking of post tensioned beam,the formulas for calculating of the anchorage losses and anti-friction influence length are derived.An example of continuous cantilever construction is given to compare the error between the calculation results of anchorage losses and anti-friction influence length and the exact value in the current railway bridge code and highway bridge code to reveal the irrationality of the calculation method for the anchorage losses and anti-friction influence length of pre-stressed tendon in the current code in China.In addition,the effects of distance from the intersection of the straight section at the bridge end and the arc line to the horizontal projection distance at the bridge end,arc radius and radius angle on the anchorage loss of bridge end are studied.The results show that the anchorage loss at the intersection point of the straight section and the arc line at the end of the bridge is 5.0%higher than the exact value according to the railway bridge code,and 36.7%lower than the exact value of according to the highway bridge code.The calculation results according to highway bridge code are seriously distorted.Meanwhile,the anchorage loss of the bridge end can be reduced by increasing the horizontal projection distance from the intersection point of the bridge end and the arc line to the bridge end,increasing the arc radius and reducing the radius angle.