Field-Based Characterization of Stay Cables: Traffic-Induced Fatigue Demand and Wind-Vibration Susceptibility

Abstract

Stay cables are critical components of cable-stayed bridges and are subjected to repeated stress fluctuations induced by traffic and wind, which may contribute to fatigue damage and vibration-related deterioration. This study presents a field-based experimental investigation of two stay cables of the Ing. Antonio Dovalí Jaime Bridge using simultaneous strain and acceleration measurements obtained during a controlled static load test and under normal operating conditions. Natural frequencies and modal damping ratios were identified from acceleration records, while effective flexural stiffness and mass per unit length were estimated using a mechanical cable model. Effective axial stiffness was determined from measured strain increments and corresponding tension-force variations. The identified properties were then used to estimate live-load-induced tension histories during bridge operation. Stress histories in the prestressing strands were processed using rainflow counting to obtain stress-range distributions and equivalent stress ranges, which were compared with an infinite-life fatigue threshold. Wind-vibration susceptibility was additionally assessed using the identified modal damping ratios and a Scruton-number-based reference criterion. The results indicate low traffic-induced fatigue demand during the monitored period, while the low modal damping ratios suggest potential susceptibility to wind-induced vibrations. Overall, the field measurements provide a direct characterization of stay-cable mechanical properties and support a screening-level evaluation of traffic-induced fatigue demand and wind-vibration susceptibility.