Analysis of non-uniform force distribution characteristics among tendons of prestressed anchor cable and experimental study on equal stress tensioning

Abstract

Non-uniform force distribution among the tendons of prestressed anchor cables significantly impacts the performance and reliability of anchoring systems in geotechnical engineering. This study addresses the quantification of this variability through the development and validation of a "non-uniformity coefficient (δ)" using in situ experiments on 112 anchor cables. The research establishes a novel methodological framework that combines single-tendon and whole-bundle pull-out tests to precisely measure and analyze force distribution. Through these tests, the study reveals that 61.61 % of the cables exhibit moderate to extreme non-uniformity, particularly impacting cables with fewer tendons and longer free segments. A reduction coefficient of 0.75 is proposed to account for the impact of non-uniform forces on the theoretical limit of bearing capacity. The study develops and implements innovative equal stress tensioning equipment, further investigating its effectiveness in achieving uniform force distribution across anchor cables, demonstrating significant improvements in force uniformity and reductions in prestress loss, with non-uniformity coefficients improving from 0.6 to below 0.1 and prestress losses decreasing from 25.85 % to below 11 %. The wedge push lock-off and retraction control method is also analyzed, reducing prestress loss by approximately 27.35 % in single-tendon anchors and 16.63 % in six-tendon anchors. These findings not only enhance the understanding of non-uniform force distribution in anchor cables but also contribute innovative solutions that could significantly influence the design and operational strategies of geotechnical anchoring systems, particularly in complex engineering environments.