Full span box girder
A full-span box girder is a type of bridge structure component that consists of a hollow box-like cross-section extending along the entire span of the bridge. It is typically made of reinforced concrete or steel. The box girder has a closed cross-sectional shape, which provides high torsional stiffness and bending resistance. It usually has top and bottom flanges connected by vertical webs. The top flange serves as the bridge deck, while the bottom flange and webs contribute to the overall strength and stability of the structure.
Advantages
High Structural Efficiency: The box girder's design distributes loads evenly, allowing it to carry heavy loads with relatively less material compared to other structural forms. This results in a more efficient use of resources and reduced construction costs.
Good Torsional Resistance: The closed box shape provides excellent torsional stiffness, which is crucial for bridges subjected to lateral forces or eccentric loads. It helps prevent excessive twisting and deformation of the bridge structure.
Smooth and Aesthetic Appearance: Box girders often have a sleek and streamlined appearance, making them aesthetically pleasing. They can enhance the visual appeal of a bridge and blend well with the surrounding environment.
Versatile Application: Full-span box girders can be used in various types of bridges, including highway bridges, railway bridges, and pedestrian bridges. They can adapt to different spans, terrains, and loading conditions.
Construction Methods
Cast-in-Place Method: In this method, the box girder is constructed on-site by pouring concrete into formwork. The formwork is carefully assembled to create the desired shape and dimensions of the box girder. Reinforcing steel bars are placed within the formwork to provide strength. This method allows for greater flexibility in design and can be used for complex geometries.
Precast Method: Box girders can also be precast in a factory and then transported to the construction site for installation. Precast box girders offer several advantages, such as higher quality control, faster construction speed, and reduced on-site labor. They are typically fabricated in segments and then joined together on-site using various connection methods.
Applications
Full-span box girders are widely used in modern bridge construction due to their numerous advantages. They are commonly employed in long-span bridges, where their high strength and stiffness are essential for spanning large distances. Some specific examples of bridges using full-span box girders include cable-stayed bridges, suspension bridges, and continuous beam bridges.
