Effect of symmetrical broken wires damage on mechanical characteristics of stay cable

Abstract

Broken wires are a common damage in stay cables due to aging and harsh environment. However, the analytical method to study the effect of broken wires on the mechanical characteristics of stay cables is still limited. Therefore, based on the microstructural mechanical model of damaged multi-wire cable, this paper proposes an analytical method for the static and dynamic characteristics of cables with broken wires. The broken wire damage is equalised to the axial stiffness reduction in the end-sliding region and recovery region of the broken wire. Governing equations for static configuration and in-plane free vibration of damaged multi-wire cable are then established. Cables with different physical parameters are studied to research the effect of broken wire damage on the static and dynamic characteristics. The results reveal that an increase in the number of symmetrical broken wires linearly decreases the horizontal component of cable tension in piecewise, linearly increases the sag and decreases the in-plane natural vibration frequency in piecewise. Besides, the cable sag is sensitive to the location of broken wire damage, while the horizontal component of cable tension and natural frequency are not sensitive to the location of the broken wire damage. Under the same broken wire damage, the closer the damage is to the support, the greater the sag is. When the broken wire percentage reaches 18.9% at the mid-span, the relative reduction in horizontal component of cable tension is 1.7%, the relative increase in sag is 1.7% and the relative decrease in the in-plane natural vibration frequency is about 0.85% for 100 m long cable. Meanwhile, broken wire damage hardly alters the static characteristics of the initial slack cable with an aspect ratio greater than 1.002. However, the effect of the broken wire on the static characteristics of the initial taut cable nonlinearly increases with a decreasing aspect ratio. Moreover, the effect of broken wire damage on this cable's static characteristics nonlinearly decreases when the cable length increases. Hence, broken wire damage remarkably influences the static characteristics of short cable.