Structural capacity and fatigue performance of ASTM A709 Grade 50CR steel

ASTM A709 Grade 50CR steel includes a range of 10.5% to 12.5% chromium, which greatly enhances the corrosion resistance of this type of steel in comparison to conventional steels widely used for structural applications. Despite the wealth of information on the durability of ASTM A709 Grade 50CR steel in corrosive environments, there was a gap in the literature concerning how this type of steel responds to the loads that the structures experience during their service life. To investigate this critical aspect and facilitate the future use of corrosion-resistant steel, the current study devised a holistic structural testing program with a focus on bridge applications. For this purpose, a full-scale girder was designed, fabricated, and tested under a four-point bending setup. The girder's ability to meet the design expectations was assessed by comparing the results to the requirements of AASHTO Bridge Design Specifications. In addition, several tensile and fatigue tests were carried out to obtain an in-depth understanding of the performance of ASTM A709 Grade 50CR steel under both monotonic and cyclic loading scenarios. This led to the development of load–displacement, stress–strain, and S-N curves. The investigations were then expanded to quantify the remaining capacity of three different types of steel, i.e., corrosion-resistant steel, weathering steel, and carbon steel. For this purpose, a set of simulations were performed to estimate the corrosion rate and section loss of the girders under consideration over time. The outcome of this holistic study contributed to providing the insight necessary for the safe and efficient design of structural members made with corrosion-resistant steel.