Temporal and spatial variability of corrosion of high-strength steel wires within a bridge stay cable

Abstract

The temporal and spatial corrosion variability of high-strength steel wires has a significant influence on the service performance deterioration behaviors of bridge stay cable. To proposed quantitative descriptions of the temporal and spatial variability, three different kinds of specimens are manufactured by Galvanized steel wires, and the accelerated corrosion experiments are conducted. For the single-wire specimens, the uniform corrosion process, the variation of surface microtopography and the time-dependent pitting corrosion model are investigated. In addition, the spatial corrosion variability of wires within a cable cross section is investigated by considering different damage conditions of sheath. It is found that the uniform corrosion process of the single-wire specimen can be divided into two stages, which correspond to the corrosion of Galvanized coating and substrate, respectively. The variability of uniform corrosion depth decreases firstly and then tends to be steady. The microtopography of corroded wire surface tends from compact spherical structure to be porous, hollow and loose. In the second corrosion stage, the corrosion products seem to be small clumps fluffy or flowery floccule, and then tend to be lamellar cross form and sand granular. The block maximum pitting factor of a single wire can be described by Gumbel distribution, and in the developed time-dependent model, both the location parameter and scale parameter decrease exponentially in the first corrosion stage and linearly in the second corrosion stage. The corrosion process difference factor of wires in adjacent layers of stay cable can be described by Normal distribution when the sheath is globally aging, and the mean value and coefficient of variation are 0.6758 and 0.2543, respectively. The spatial corrosion variability of cable wires is significantly affected by the broken shape of sheath. The difference of global corrosion degree of wires in different layers decreases with the extension of the exposure period. The sheath with rectangular broken shape and quadrate broken shape will lead to stronger spatial corrosion variability in cable wires than that with semi-annular broken shape.