Reliability assessment of parallel wire suspender components considering interlayer corrosion variance

The suspenders bear the repeated stress caused by various cyclic actions during the bridge operation while the stress amplitude under dynamic load is smaller than under dead load. The steel wire degradation process is a typical corrosion fatigue degradation, in which the initial defects caused by surface corrosion are the main source of fatigue cracks and the crack development under operating load leads to the failure of the steel wire. The steel wires of the suspender are considered as a co-deformed parallel structural system. The corrosion process of steel wires in different layers are different for the diffusion paths of corrosion medium, which makes the bearing capacity of steel wires differs from each other. The suspender strength depends on the wire of lowest strength due to the Daniels effect, interlayer corrosion variance should be considered in the evaluation of suspender reliability. This paper investigates the interlayer corrosion variance of parallel steel wire suspenders on the basis of neutral salt spray test. It proposes a corrosion variance coefficient, and considers the stochastic degradation process of suspender. Combined with the daily traffic model, it establishes a sophisticated reliability evaluation method of suspender. The results are shown: The steel wires in each layer of test specimens are all severely corroded when the corrosion time reaches a certain degree. For the specimens with different damage types, the overall corrosion condition of the annular damaged specimen is the most severe; whereas that of the vertical damaged specimen is the least. Under experimental environment, the corrosion variance coefficients of sheath damaged specimens follow normal distribution. In the application of suspender evaluation, the service lifespan of wires varies obviously with the corrosion variance coefficient. The distribution of steel wire lifespan under different corrosion variance coefficients also follows normal distribution. The service lifespan of outer layer wires is longer than inner layer wires, and the overall reliability lies between the reliability of outer and inner layers.