2026 Volume 5 Issue 1 Pages 127-135
This study evaluates the feasibility of extending inspection intervals for concrete railway bridges managed by JR East. Under current regulations, general inspections of railway structures are mandated every two years. However, when detailed examinations confirm sufficient durability, the interval for concrete structures may be extended up to six years. The interpretation of the “Standards for Maintenance of Railway Structures and Commentary” imposes strict conditions for such extensions, including limiting eligibility to S-rated structures and requiring more than ten years since the initial inspection. These constraints result in only marginal reductions in inspection workload.
To explore practical alternatives, ten years of inspection data were analyzed using a count-based transition matrix to assess deterioration progression. Results indicate that even when the inspection cycle is extended to six years, the increase in the probability of progression to the most severe condition (A rank) remains minimal. Furthermore, a case study was conducted on an actual structure exhibiting minor defects. Structural capacity was verified through allowable stress checks, incorporating a ten-year forecast of corrosion effects. The analysis confirmed that the structure would continue to meet required performance standards, supporting the feasibility of interval extension.
Based on these findings, it is concluded that extending inspection intervals up to six years is operationally reasonable, even for structures with minor deterioration, provided that functional performance is assured. This approach offers potential for reducing inspection workload while maintaining safety and reliability. Future work will focus on refining eligibility criteria, implementing risk-based management strategies, and validating the effectiveness of extended intervals in practice.
