Masonry arch bridges are regarded as the oldest examples of engineered structures in the world; and they reflect the previous civilizations in... Show moreMasonry arch bridges are regarded as the oldest examples of engineered structures in the world; and they reflect the previous civilizations in the world with their various sizes, styles, and spans. The preservation of these structures is receiving a great deal of attention in the structural engineering community. And as such, restoration, strengthening and reinforcement of historical masonry bridges have become a challenge for civil engineers. At the present time, most important problems of masonry arch bridges are heavy traffic loads and destructive natural disasters. These bridges were constructed centuries ago and they addressed the load-carrying problems of old times. With the passing of the time, the traffic changed and many natural disasters occurred. Correspondingly, loads on masonry arch bridges have increased and the traffic on the bridges have become more intense in the course of time. However, the bridges keep up to their initial performance; and this shows the complexity of their structural behaviors. This study provides the background information about masonry arch bridges and their components. It also helps us better understand the construction materials, structural properties and structural behavior of masonry arch bridges. In light of this background information, this study presents an overview of seismic retrofit for masonry arch bridges and a comprehensive study on the type, mechanism of failure and structural integrity of masonry arch bridges. M.S. in Civil Engineering, July 2011 Show less