Time-Dependent Effect of Corrosion on the Mechanical Characteristics of Stay Cable

Abstract

Cable-stayed bridges, of which there are up to 5 around the world, are often the first choice for long-span bridges. As stay cables increase in service life, rust becomes the most common challenge. At present, more than 2 cases of replacing corroded cables are underway worldwide. Inspections of replaced cables prove that corrosion is a leading cause of degradation in the mechanical behavior of cables. However, there is no accurate method of describing the law of degradation of the mechanical behavior of corroded cables and it remains impossible to evaluate the safety of stay cables in a timely fashion. Therefore, this paper reports a study on distribution model of steel wire corrosion, corrosion rate, and mechanical model of corroded cables, establishing governing equations for static configuration and in-plane free vibration of corroded cables. The paper also derives some analytical solutions for both the static and dynamic characteristics of corroded cables. The finite element method is adopted for the simulation and computation of the static and dynamic characteristics of corroded cables to reach, through comparison and analysis of the results of the two methods, the following conclusions. As corrosion time increases, the horizontal cable force of the corroded cable decreases nonlinearly, cable sag increases nonlinearly, and natural frequencies in-plane of the corroded cable present nonlinear reduction. In early corrosion stage, relative change of static and dynamic characteristics of cables is extremely small. For a corrosion time of 12 years, the average cross section area loss rate in cable corrosion region is 3%, but horizontal cable force is only reduced by 1%, cable sag rises only by 1%, and the decrease of each natural frequency in the plane is only .54%.