A Study on Maximum Span Length Optimization Based on Sensitivity Analysis of Overhead Catenary Design Parameters - Focusing on a Case Study of the Honam High-Speed Railway -

In electric railway catenary systems, the span refers to the distance between two adjacent support structures, and span length directly affects current-collection performance; catenary design must therefore specify a standard span appropriate to the operating speed. Maximizing span length is a key means of reducing the number of support poles, foundations, and cantilever assemblies, thereby directly lowering construction and maintenance costs. However, the maximum span length must be determined in accordance with the Remaining Working Width (Mw ≥ 0) criterion of UIC 606-1 OR, which is jointly governed by various catenary design parameters such as stagger, wind speed, and curve radius. This study first performs a one-dimensional sensitivity analysis, followed by a two-dimensional sensitivity analysis with derivation of safe design bands, based on the catenary design conditions of the Honam High-Speed Railway, in order to identify which of these design parameters has the primary influence on the calculation of maximum span length. The results show that the rear stagger is the most dominant parameter directly controllable by the designer, and on this basis a stagger optimization algorithm is proposed. Finally, the algorithm is validated by applying it to a general-section catenary case on the Honam High-Speed Railway under Zone 2 (Jeongeup-Gwangju), Site 2 (exposed site), and curve radius R ≥ 5,000 m. The algorithm was implemented in Python and cross-validated against the calculation program used in the original Honam High-Speed Railway detailed design; relative to the current stagger standard of -50 to -200 mm, radius-specific optimized stagger values ranging from -140 to -60 mm were obtained, securing an additional 0.5 - 4.5 m of span length across the curve radii examined. The resulting maximum span is defined strictly as the value permitted under the lateral geometric and wind-load safety condition (Mw ≥ 0) of UIC 606-1 OR. All optimized spans remain within the 65 m span limit adopted in the Honam High-Speed Railway detailed design and fall within the span range (40-65 m) presented by the dynamic-characteristics simulation results performed during the detailed design for the same catenary system.