Fatigue Assessment of Suspension Bridges under Non-Stationary Buffeting Using TSD-RFC Method

Abstract

Suspension bridges are subject to significant stress cycles over their operational lifespan due to wind loads, leading to fatigue damage. Traditional rainflow counting methods have limitations when applied to non-stationary wind loads, particularly when the stress response exhibits significant state changes, which can result in incomplete cycle identification or amplitude misjudgment. This paper proposes a Time-Domain-State Dual-Layer Rainflow Counting (TSD-RFC) method to address these shortcomings in fatigue analysis of suspension bridges under non-stationary wind loads. The method decomposes the non-stationary response signal into multiple quasi-stationary segments, applying the classical three-point rainflow counting method within each segment to identify primary fatigue cycles. Additionally, for state transition segments in the response, an independent state transition cycle counting layer is used to identify additional large-amplitude stress cycles induced by wind speed fluctuations. Comparison with traditional rainflow counting shows that the TSD-RFC method more accurately identifies stress cycles, particularly in high-amplitude stress regions, effectively distinguishing cycles caused by state transitions. In the fatigue assessment of suspension bridges, the TSD-RFC method results in approximately 11.39% higher fatigue damage than traditional methods at a wind speed of 20 m/s, demonstrating the significant advantages of this method in fatigue damage evaluation under non-stationary wind loads.