Implementation of load rating provisions for highway arch bridges

Arch bridges are amongst the oldest and most common types of bridges used by engineers. Some of the arch bridges built during the Roman Empire, such as the Pont du Gard and the Pont Saint Martin, are still standing today. They are preferred by many engineers and architects due to their aesthetically pleasing appearance, versatility in construction materials, and their ability to accommodate high vertical clearances. Arches have been commonly used in both highway and railroad bridges. Prior to the industrial revolution, arch bridges were built using stone or bricks. Then, steel and concrete arch bridges became more commonly used. Concrete and masonry arches are usually used for short spans, whereas steel arch ribs are used to accommodate longer span lengths. Many of these arch bridges have been in service for several decades and have experienced significant deterioration. These bridges require accurate load rating to assess their condition and evaluate the need for maintenance and rehabilitation work. The load rating of arch bridges can be a challenging task due to the combined effects of axial forces, bending moments, temperature changes, and second-order moments from member buckling. There are several steel arch bridges in America that represent an essential part of the highway and transportation system. Most of these bridges have been in service for more than 50 years. The codes and guidelines used for designing these bridges are outdated and may not be compatible with the current design standards and moving load conditions. Furthermore, these bridges may have experienced corrosion, material losses, and other deterioration effects that can reduce the load carrying capacity of the bridge. Therefore, it is essential to perform load rating for these bridges to determine the need for strengthening and repair work. This paper demonstrates the implementation of the load rating provisions for a major arch bridge in America. The bridge is a steel arch highway bridge which is rated based on the Load and Resistance Factor Rating (LRFR) provisions in AASHTO Manual for Bridge Evaluation (2011) . The analysis procedure and application of the load rating equations in the code are demonstrated.