Abstract:

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.
 

Key words: concrete box beam, vertical prestressing, constructing localization error; , the inspection method of Pearson χ², curve Pearson-Ⅲ, prestress loss of instant anchoring