# Corrosion Fatigue Assessment of Bridge Cables Based on Equivalent Initial Flaw Size Model
## 5 Conclusions  
This study presents a lifespan calculation model based on the EIFS method to analyze the various stages of corrosion wire lifespan. Using this lifespan calculation model, the influence of corrosion and corrosion fatigue coupling on the lifespan of corroded wires is quantitatively discussed. Furthermore, the corrosion fatigue lifespan of the parallel wire suspension cable is investigated based on the series-parallel fiber bundle model. The Runyang Suspension Bridge is used as a case study to evaluate the corrosion fatigue damage evolution of bridge cables during service. Several conclusions can be summarized as follows:  
1. Building upon the EIFS method calculation model, this study further analyzes the influence of corrosion and fatigue load coupling on the corrosion fatigue performance of rusted steel wires. The results indicate that under corrosion fatigue conditions, the initiation of cracks in steel wires is more prone, and their fracture toughness is further reduced. However, this coupling effect does not increase the number of fatigue sources. The factors affecting the number of fatigue sources are primarily the number of pits along the circumference of the steel wire. 2. Based on the series-parallel fiber bundle model, a corrosion fatigue full lifespan model for parallel wire suspension cables is provided. The parallel wire cables are simplified as independent individual wires connected in parallel. The corrosion propagation model is used to consider the interrelation between each wire, and the conversion criteria are applied to calculate the corrosion fatigue full lifespan of the parallel wire suspension cables. 3. A case study of the Runyang Suspension Bridge is taken, and the stress time history spectra of short cables near the central clamp are measured. The analysis results of the case study demonstrate that under weak corrosion conditions, the cable wires of the Runyang Suspension Bridge under traffic load will not experience corrosion fatigue fracture during the design reference period. Even under severe traffic loads (calculated based on an equivalent stress amplitude of 70 MPa), the cables can still serve safely. When the steel wire has initial defects, the fracture lifespan under corrosion fatigue conditions depends on the strength of the corrosive medium. The  
Figure 21: Lifespan of cable wires in severe environment. effect of the medium on crack propagation is evaluated using the \(C_{cor}\) value, with a larger \(C_{cor}\) value indicating a more severe reduction in lifespan. Even under low stress amplitudes, the steel wires may still experience fracture within the design reference period. * The influence of the environment is considered using conversion factors. The calculation results indicate that the reduction in corrosion fatigue lifespan in a corrosive environment is significantly greater than that due to heavy loads. For a 109-wire suspension cable, the lifespan under severe loads (equivalent stress amplitude of 70 MPa) is approximately 93 years, while in a severe corrosive environment, the lifespan is about 39 years. Therefore, when constructing or maintaining suspension cable facilities, the impact of environmental corrosion should be considered as a primary factor. Conceptualization, T.G. ; methodology, T.G. and X.Y. ; software, Z.L. ; validation, X.Y. and S.N. ; formal analysis, T.G. and Z.L. ; investigation, Z.L and X.Y. ; resources, T.G. ; data curation, Z.L. and X.Y; writing--original draft preparation, Z.L. and X.Y; writing--review and editing, T.G., S.N. and J.C.; visualization, T.G. ; supervision, T.G. ; project administration, T.G. and J.C.; funding acquisition, T.G. All authors have read and agreed to the published version of the manuscript. This research was funded the Provincial Policy Guidance Program of Jiangsu (grant No. BZ021011), the Natural Science Foundation of Jiangsu Province (grant No. BK20210257), the Natural Science Foundation of China (grant Nos. 51978156 and 52108272), and the National Key R&D Program of China (grant No. 2022 YFB2602700).