Girder bridges represent the most straightforward structural form and are characterized by steel beams configured into either an I-section or a box section, denoted as a plate girder bridge or a box girder bridge, respectively. These bridges consist of deck slabs, traversed by vehicles and pedestrians, and primary girders that provide support to the deck slabs. Deck slabs encompass various types, including RC (Reinforced Concrete) deck slabs, steel deck slabs, composite deck slabs, and PC (Pre-stressed Concrete) deck slabs. The stability of this system is ensured by cross girders and cross bracings strategically positioned at intervals.
Composite Girder Bridges, a category of bridges, are characterized by the collaboration between deck slabs and main girders in resisting loads. Plate and box girder bridges, the two prevalent types of modern steel girder bridges, are often referred to interchangeably with the term “girder” replacing “beam” in bridge design contexts.
A plate girder, a type of built-up I-beam section, is specifically engineered to bear heavy loads. Fabricated through the riveting or welding of steel plates into an I-beam configuration, plate girders with spans exceeding 9.15 meters incorporate web plates and flange plates to form a built-up beam or I-section. Generally applicable for effective spans ranging from 25 to 150 meters, plate girders find extensive use in areas characterized by high traffic volumes and the need for longer-span bridges.