**6.1 Elements of deterioration in steel bridges**

Corrosion is the major element of deterioration in steel structures. Fatigue damage and brittle fracture are special problems for steel structures resulting from repetitive loadings over a long period of time. As Contreras-Nieto et al. [8] state in their paper as a significant number of steel bridges are approaching the end of their service life, understanding deterioration characteristics and rate of deterioration will help bridge stakeholders prioritize bridge maintenance, repairs, and rehabilitation. One prediction model uses data mining techniques to include logistic regression, decision trees, neural networks, gradient boosting, and support vector machine to the United States' national bridge inventory to estimate the probability of steel bridge superstructures reaching deficiency. The model uses data based on the defined scope of the research: design material (steel), type of design (stringer/multi-beam or girder), and deck type (cast-in-place concrete). The predictors of the model include age, average daily traffic, design load, maximum span length, owner, location, and structure length. The magnitude that these factors contribute to the likelihood of a steel bridge superstructure's deficiency was identified. Outcomes of the analysis afford bridge stakeholders the opportunity to better understand the factors that are correlated to steel bridge deterioration as well as provide a means to assess risks of superstructure deficiency for the sake of prioritizing bridge maintenance, repair, and rehabilitation [8]. The prediction model the author proposes considers a wide range of factors which correlate to a risk assessment on the rate of deterioration of the steel structure, with which the owners can determine maintenance and rehabilitation priorities.
