Localized corrosion monitoring and quantitative evaluation of steel wires in the splay saddle using distributed optical fiber sensing technology

Steel wires in the splay saddle of suspension bridges are highly susceptible to corrosion due to a highly exposed environment, moisture, and corrosive media retention, and limitations of protective measures. Existing optical fiber strain monitoring (using conventional spiral-wrapping) fails to quantify corrosion on small-diameter wires. This study optimizes a corrosion-resistant fiber deployment scheme. Accelerated corrosion tests with customized wire tensioning device reveal that wire corrosion creates cross-sectional discontinuities, forming high-stress zones with a diagnostic bimodal strain distribution for precise corrosion localization. Corrosion zone strain evolution shows three stages—uniform, non-uniform, and critical fracture—quantified by strain heterogeneity. Key influences include initial strain, corrosion length/rate, and load variations. A quantitative theoretical model linking fiber strain response to corrosion degree was established, incorporating a correction factor K to reduce maximum average relative error to <3%. This enables distributed optical fiber sensing to accurately assess steel wire corrosion severity.