Steel box girder is composed of top plate, bottom plate, web, transverse partition and longitudinal and transverse stiffeners. Its commonly used cross-sectional forms include single box single room, single box three room, double box single room, three box single room, Multi-box single-chamber, inverted trapezoid with inclined webs, single-box multi-chamber with more than 3 webs, flat steel box girder, etc. Among them, the most widely used steel box girder section is double-box single-chamber, and multi-box single-chamber is used for bridges with larger bridge widths. Flat steel box girder has a small ratio of beam height to beam width, and is mainly used for ribbed beams such as suspension bridges, cable-stayed bridges, and arch bridges. It is rarely used in beam bridges. Single-box multi-chamber steel box girder with more than 3 webs is not easy to manufacture and install, so it is rarely used.
It is divided into several beam sections for manufacturing and installation, and its cross section has the characteristics of wide and flat shape, and the aspect ratio reaches about 1:10. Steel box girder is generally formed by fully welding the top plate, bottom plate, web, and transverse partitions, longitudinal partitions and stiffeners. The top plate is an orthotropic bridge deck composed of a cover plate and longitudinal stiffeners. The thickness of each plate of a typical steel box girder can be: cover thickness 14mm, longitudinal U-shaped rib thickness 6mm, upper mouth width 320mm, lower mouth width 170mm, height 260mm, spacing 620mm; bottom plate thickness 10mm, longitudinal U-shaped stiffeners ; The thickness of the inclined web is 14mm, the thickness of the middle web is 9mm; the spacing of the transverse partitions is 4.0m, and the thickness is 12mm; the beam height is 2～3.5m.
1. Light weight and material saving
2. Bending and torsional rigidity is large
3. Easy installation, low cost, short cycle
4. Guaranteed quality and quantity, and high reliability.
5. High construction efficiency and high safety
6. Widely used
Because of its structural form, steel box girder is generally used for municipal elevated and ramp steel box girder; construction period traffic organization long-span cable-stayed bridge, suspension bridge, arch bridge stiffening girder and pedestrian bridge steel box girder.