Evaluation of Residual Strength of Polyester Lines Considering Breakage of Some Strands

To accurately assess damaged polyester lines’ residual strength, this study takes commonly used engineering spiral-strand unjacketed polyester lines as the research object, and first proposes a strand rearrangement-based evaluation method. It accounts for subropes/strands’ load-bearing and damage states, analyzes damage-induced changes in component geometric parameters and mechanical properties, clarifies compensation length’s critical impact on damage location/residual strength, and addresses existing models’ lack of internal variation mechanism analysis. It also classifies residual strength/stiffness under different lengths/damage distributions, elucidates damaged subropes’ load evolution (slack to tensioned) and "abrupt tension gradient change"’s engineering significance, and establishes test result selection criteria. Experimentally verified, it is reliable, characterizes damaged polyester lines’ mechanical behavior accurately, provides theoretical support, and supplements deep learning.