# Corrosion-Fatigue Evaluation of Uncoated Weathering Steel Bridges
## 2 Literature Review  
Extensive efforts were made by researchers on the C-F process of weathering steel. [PERSON] et al. [13] predicted the fatigue life of the aged car-body. In the analysis, the effect of corrosion on the car-body was simulated by proportionally reducing the plate thickness with the time. As a result, when considering corrosion, the fatigue life of the car-body was decreased by 20% and 40% for the 23-years old car and 40-years old car, respectively. [PERSON] et al. [14] studied the fatigue performance of weathering steel Atmofix 52 in corroded and non-corroded situations. The result was expressed by the fatigue strength at \(1\times 10^{7}\) cycles under two stress ratios, i.e., \(R=-1\) and \(R=0\). When the stress ratio equals to \(-1\), the fatigue strength of non-corroded steel and corroded steel was 240 MPa and 140 MPa, respectively. Under the stress ratio of zero, the two values were respectively 190 MPa and 120 MPa. Overall, the fatigue strength of corroded steel could be significantly lower than that of uncorroded steel. [PERSON] et al. [15] investigated the fatigue performance of weathering steel A588 in two corrosive environments, including pure water and salt spray. The result indicated a significant increase in the fatigue notched factor, which reflects the degradation in fatigue strength. According to the result, the fatigue notched factors of sheltered welded steel beam were 1.52 and 3.07 in pure water and salt spray, respectively. At the same time, the fatigue notched factors of the sheltered plate steel beam were respectively 2.56 and 3.01 in pure water and salt spray. Several similar studies also demonstrated the degradation in fatigue performance under the corrosion, especially in the chlorine-rich environment [10; 16]. [PERSON] [17] studied the fatigue strength of bolted connections, which indicates that corrosion can influence the fatigue life of the joint. Moreover, extended studies were done by [PERSON] et al. [18; 19] that showed the degradation of the corroded bolted joint due to pitting corrosion. Besides, relevant studies suggested that the pitting flaw initiated by corrosion could be regarded as the source of fatigue cracking [14; 16; 20]. However, since the C-F process is a highly complicated issue, few models can be yet found on the C-F issue of steel bridges. As a matter of fact, the most reliable way to investigate the C-F process is the fatigue test under the corrosive environment. However, the corrosion is such a long-term process that it is difficult to be incorporated in the fatigue test employing a relatively high loading frequency (from 5 to 50 Hz). Alternatively, pre-corroded specimens were commonly used in the fatigue test [7; 10]. [PERSON] et al. [21] made specimens with corroded ship building steel in seawater, and the result showed that the fatigue strength decreases from FAT 86 to 64.95 MPa. In this case, the whole C-F process cannot be revealed comprehensively since the two interactive processes are artificially separated in the test. Generally, [PERSON] [16] claimed that the pitting corrosion is believed as the dominating effect at the early stage of the C-F process. On this end, the electrochemistry theory has been applied to evaluate the pitting corrosion process, which has been validated by the experimental data on aluminum alloy, stainless steel and crude steel [22; 23]. Under this content, the electrochemistry theory is employed to describe the time-dependent development of pitting flaws, which can be regarded as the initial flaw in the crack propagation. Nevertheless, it is still difficult to find a way to couple the two processes systematically. Thus, efforts are now gradually made to combine the electrochemistry theory and fracture mechanics in describing the C-F process of metal materials [10; 23; 24]. For instance, according to the article [10], under the pitting corrosion the initial flaws will be generated on the exposed material surface at the beginning of the C-F process.