## 1 Introduction  
Weathering steel is composed of ordinary carbon steel and small amounts of corrosion-resistant elements, such as copper and nickel. The atmospheric corrosion resistance of weathering steel is 2-8 times that of ordinary carbon steel, and the coating life of coated weathering steel is 1.5-10 times that of ordinary carbon steel [1]. Measured by the cost of the entire life cycle, the cost of uncoated weathering-steel bridges is lower than that of ordinary carbon steel bridges [2, 3]; thus, the application of weathering steel in bridges is gradually increasing. In order to maximize the atmospheric corrosion resistance of weathering steel, weathering steel should be used in its uncoated form. However, pitting corrosion may occur on the surface of weathering steel, which may cause stress concentration. Under the repeated action of traffic loads, fatigue cracks may develop in the pits and cause final fatigue failure. Therefore, there are potential fatigue problems in weathering steel bridges. [PERSON] et al. [4] studied the fatigue life of weathering-steel transverse stiffeners, cover plates, and other fatigue details exposed to the atmosphere for many years and found that fatigue cracks were more likely to appear, and developed faster, in a humid environment; the greater the stress concentration of the fatigue details, the less the fatigue life was affected by corrosion. [PERSON] [5] investigated the life degradation of weathering-steel base materials exposed to the atmosphere for 2 and 4 years, of weathering-steel butt welds,weathering-steel non-load-carrying fillet welds, and of weathering steel covers exposed to the atmosphere for 11 years and found that the corrosion pits caused the increase in surface roughness of the weathering steel and, therefore, the stress concentration, which led to a decrease in fatigue life. [PERSON] et al. [6; 7] studied the fatigue life of the fatigue details of A588 weathering-steel hand-welded transverse stiffeners exposed to the atmosphere for 2 and 4 years and results showed that corrosion reduced the fatigue life of the specimen by up to 22%. [PERSON] et al. [8; 9] then conducted an experimental study on the fatigue life of the fatigue details of A588 weathering-steel automatic submerged arc-welding transverse stiffeners exposed to the atmosphere for 3 years and 8 years, and also on that alternately exposed to the atmosphere for 3 years, and their results indicated the fatigue lives of the corroded specimens were 42%, 54%, and 42% lower, respectively, than the uncorroded samples; corrosion led to pitting and stress concentration, which in turn resulted in a decrease in fatigue life. [PERSON] et al. [10] tested the fatigue life of Atmofix 52 weathering-steel specimens exposed to the atmosphere for 20 years and showed that the fatigue life of corroded steel was much lower than that of uncorroded steel under symmetrical cyclic loading; the occurrence of fatigue cracks was highly related to the surface roughness caused by corrosion pits. [PERSON] et al. [11; 12; 13; 14] experimentally studied the fatigue life of uncorroded and corroded Q235 ordinary carbon-steel specimens, and it was found that the shape of the corrosion pits gradually developed from the narrow and deep type to the wide and shallow type; the fatigue life of the component decreased with the increase in the degree of corrosion, and the fatigue life of the components with a corrosion degree of 15% was only 3% that of the uncorroded components. The characteristic curved surface of the corroded surface was fitted with a PS50 three-dimensional non-contact surface profiler and Geomagic Studio software, and it was then exported to ANSYS to obtain the fatigue notch coefficient; fracture analysis showed that the fatigue cracks in almost all components, at different corrosion levels, were initiated by the corrosion pits. [PERSON] and [PERSON] et al.