Corten Steel: Corten steel is an untreated steel that will weather and/or rust. Corten steel products can stain the surfaces below them. Clear coating the steel will not prevent rust or weathering of the metal.
Weathering steel is a high-strength, low-alloy steel which has been proven to provide a significantly higher corrosion resistance than regular carbon steel. This corrosion resistance is a product of the small amounts of alloying elements added to the steel, which enable it to form a protective oxide layer when exposed to the environment. The main advantage of its use in bridges is that, under normal conditions, it may be left unpainted, leading to significantly reduced maintenance and environmental costs. Weathering steel has been a material of choice for highway structures for almost half a century, and a very large number of structures have been constructed with it. Although its use has for the most part been successful, it has also become evident that, in circumstances where there is the presence of salt and sulphur oxides, its performance is deficient. In these situations the corrosion penetration rate is much higher than expected, and the oxide layer forms in thick layers. This presents an added risk, since these layers flake off and fall onto the roadway. The degree of corrosion on structures can be very different, even if the structural type, location, and climate are similar. Therefore the focus of the thesis is on the lifespan of weathering steel highway structures. Primarily this research is concerned with the effect of corrosion on the integrity of these structures, as well as ways of quantifying corrosion loss and protecting the structure from further corrosion. In order to determine the lifespan of weathering steel highway structures subject to different rates of corrosion, a probabilistic structural analysis program has been developed to assess the time-dependent reliability of the structure. This program used iterative Monte Carlo simulation and a series of statistical variables relating to the material, loading, and corrosion properties of the structure. A corrosion penetration equation is used to estimate thickness loss at a selected interval, and the structural properties of the bridge are modified accordingly. The ultimate limit states of shear, moment, and bearing, and the fatigue limit state of web breathing, are taken into account. Three types of structures are examined: simply-supported box and I-girder composite bridges, and a two-span box girder bridge.