Calculation method of post-tensioned prestressed anchorage loss considering influence of asymmetric friction

To improve the calculation method of prestressed anchorage loss of post-tensioned prestressed concrete beams with mixed straight lines and curves and enhance the theoretical calculation accuracy of the prestressed anchorage loss, an static equilibrium equation was established for the micro-segment of prestressed steel bundles. According to the deformation coordination relationship and stress continuity conditions between different steel bundle shapes, the actual influencing parameters of the mixed distribution of straight lines and curves of the prestressed steel bundles as well as the difference between the positive friction and anti-friction losses in design were considered. A piecewise approximation theory for calculating the anchorage loss of prestressed mixed bundles was established. The exact calculation formula of the prestressed anchorage loss was deduced, and a Python program was compiled to realize an automatic solution and simplified calculation. Through the field full-scale model test, the calculation errors of the exact formula and the theoretical algorithm for the prestressed anchorage loss in the current highway and railway bridge design codes were compared. Research results show that the anti-friction effect of post-tensioned prestressed bundles with mixed straight lines and curves for anchorage is smaller than the positive friction effect during the tensioning, and the actual anti-friction influence length greatly deviates from algorithms in the current bridge design codes. The anti-friction influence range calculated by the proposed method is generally closer to that in the Chinese railway bridge design code and is 16. 7% and 14. 9% higher than the current highway and railway bridge design codes in terms of accuracy and dispersion, respectively. Furthermore, it is highly correlated with the model test data, with small variability. In the related research on the post-tensioned prestressed concrete structures, the influences of the shape of actual prestressed mixed straight lines and curves, as well as the asymmetric positive friction and anti-friction effects, should be considered, and the piecewise approximation method should be used to calculate the prestressed anchorage loss of steel bundles. In the design of post-tensioned prestressed concrete structures, it is recommended to use the current railway bridge design code to calculate the anti-friction effect from the perspective of simplifying the calculation. 6 tabs, 17 figs, 30 refs. © 2022 Chang'an University. All rights reserved.