A plate girder bridge is a type of bridge supported by two or more large steel girders that are built up from separate plates rather than rolled as a single beam. These girders are typically I-shaped, formed by welding or fastening vertical webs and horizontal flanges together to carry loads efficiently. Plate girder bridges are commonly used for short to medium spans and can carry road or rail traffic. They are usually prefabricated and reinforced with stiffeners to prevent buckling and improve strength under load. (Wikipedia)