Advantages And Disadvantages Of Steel Box Girder

The steel box girder is hollow inside, with flanges on both sides of the upper part, similar to a box, divided into single box, multiple boxes, etc. Box girder of reinforced concrete structure is divided into prefabricated box girder and cast-in-place box girder. The box girder combined with bridge erecting machine prefabricated on an independent site can be erected after the completion of the lower project, which can speed up the progress of the project and save the construction period; cast-in-place box girder is mostly used for large continuous bridges.

There are two common types of materials, one is prestressed reinforced concrete box girder and the other is steel box girder. Among them, the prestressed reinforced concrete box girder is constructed on site. In addition to the longitudinal prestress, some are also equipped with transverse prestress; the steel box girder is generally processed in the factory and then transported to the site for installation. It has an all-steel structure and some parts. Add a reinforced concrete paving layer.

Box girder construction requires internal molds. The box girder has a large tonnage. Highway bridges with a span of 20-40m basically use prefabricated small box girder or T-beam. Prefabricated small box girder is currently used more because of its convenient prefabrication and good torsion resistance. many. The advantages of box girder bridges: 1. Light weight and saving steel. Because the box girder can more effectively exert the load-bearing capacity of the steel plate, the use of orthotropic steel bridge deck and the box girder with thin steel plate as the beam rib and bottom plate saves about 20% of steel. The larger the span, the more economical it is. And due to the reduced weight of the upper structure, the cost of the lower structure of the bridge can generally be reduced by 5% to 15%. 2. High bending and torsion rigidity. This is determined by the characteristics of the closed hollow section, which can provide greater bending and torsion rigidity than other section forms when the number of materials is the same, so it is especially suitable for curved bridges and linear bridges that bear larger eccentric loads. 3. Quick installation. It is convenient to maintain the box girder and can be made into a large installation unit in the factory, thereby reducing the number of connection bolts on the site. During construction, it is convenient for longitudinal dragging or erection by jacking method. The box beam is simple in structure, easy to paint, and because the inside is a closed space, it is easier to resist rust. 4. Suitable for making continuous beams. This is because its cross-sectional form can provide almost equal capacity to withstand positive and negative bending moments. 5. Novel structure, simple and beautiful appearance. my country developed a steel box girder structure in the 1980s. In 1982, a box-shaped cross-section bolt-welded railway oblique-leg rigid frame bridge with a span of 176m was built in Ankang, Shaanxi, which is still the current world record for this type of railway bridge.

In general, the small box girder has the advantages of strong torsion resistance, convenient for cast-in-place construction, and light weight. The disadvantage is that the production process is complicated and the formwork investment is relatively large. The construction can be selected according to actual needs.