This fundamental study investigates possible causes of crack initiation observed at the ends of hangers in
a through-type steel arch bridge located in Nagasaki, Japan. Through analysis of long-term measurement data and
eigenvalue analysis, it was determined that the primary factor in crack initiation was not the vibration of the hangers
themselves but rather the wind-induced buffeting response of the entire bridge structure. The vibration modes
responsible for fatigue crack development were estimated using response spectrum analysis and forced displacement
analysis. Additionally, by examining the actual damage locations and structural responses, hangers that may be
susceptible to future fatigue damage were identified. This comprehensive approach provides valuable insights into
the mechanisms of hanger end crack initiation in through-type steel arch bridges and offers guidance for preventive
maintenance strategies by focusing on the critical vibration modes identified by global analysis.
