施工定位误差对竖向预应力损失的影响研究

Research on the influence of constructing localization of vertical prestress tendons to their prestress loss

实际工程施工中,竖向预应力钢筋及锚垫板的定位都存在误差,导致锚垫板顶面和锚固螺母底面之间产生初始夹角θ,该夹角使竖向预应力钢筋在锚固时回缩量增加,竖向预应力损失增大,本研究通过现场测试分析夹角θ对竖向预应力损失的影响。在某预应力连续刚构桥施工过程中,利用SDC620三维电子寻北仪对该初始夹角θ进行测试,收集400个样本,采用皮尔逊Ⅲ曲线假设、矩估计法及皮尔逊2χ拟合检验法对样本分布规律进行分析,结果表明:初始夹角θ服从皮尔逊Ⅲ曲线分布。利用JMZX-3108AT型锚索计对竖向预应力瞬时锚固损失进行测试,结果分析表明:瞬时锚固损失F与钢筋长度l呈反比,与夹角θ呈线性关系,夹角θ对竖向预应力损失影响很大。本研究中初始夹角θ的测试方法和瞬时锚固损失的计算公式为首次提出,以期对竖向预应力设计及施工有所帮助。

The location error of vertical prestress tendons and anchor plates could lead to the appearance of the angle θ between the top surface of an anchor plate and the bottom surface of an anchoring nut,which could increase the set back amount of vertical prestress tendons and have notable influence on the prestress loss.The influence of angle θ on the prestress loss was studied.400 samples were acquired by SDC620 3D north finder to measure the angles.Regression analysis was performed assuming Pearson-Ⅲ curve and moment estimation,which was appraised using the inspection method of Pearson χ2.Comparison of results showed that the angle θ followed the distribution of Pearson-Ⅲ.Prestress loss of instant anchoring was measured by JMZX-3108AT.The results also showed that the prestress loss of instant anchoring F was in inverse proportion to the length of tendons l,and there was a linear relationship between F and the angle θ.The angle θ had significant influence on the prestress loss.The measuring method of the angle θ and the formula of prestress loss of instant anchoring were proposed,and will be helpful for the design and construction of vertical prestressing.