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Construction of Box Girder Bridge : Functions, Details, Benefits and Drawbacks

A box girder [even recognized as a tubular girder] is basically a bridge wherein the major/main beams include girders in the form of a vacant/hollow box. Furthermore, the box girder generally includes whether pre-stressed concrete, structural steel, or a combination/composite of steel as well as reinforced concrete. Moreover, the box is usually trapezoidal or rectangular in cross section.

Furthermore, box girder bridges are generally utilized for expressway overpasses/flyovers as well as with regard to contemporary raised structures of slight railway transportation. Even though, generally the box girder bridge is a type of Beam Bridge, box girders could even be utilized on cable-stayed bridges as well as additional types.

In case composed of concrete, box girder bridges could be formed in position by means of falsework supports, taken away subsequent to finishing point, or in segments in case a segmental bridge. Furthermore, box girders could even be pre-fabricated in a production work area; subsequently carried as well as set by means of cranes.

With regard to steel box girders, the girders are usually produced outside as well as raised into position through crane, having segments attached through welding or bolting. In case a composite concrete bridge deck is utilized, it is frequently cast in place by means of short-term falsework assisted through the steel girder.

Any type of the bridge could even be setup by means of the method of incremental launching. In this process, gantry cranes are frequently utilized to put new sections on the finished sections of the bridge till the bridge superstructure is built.

Functions of box girders:

  • It is utilized for contemporary raised structures of slight/light railway transportation.
  • Box girders are utilized for the creation of a curved bridge, cable supported bridge, as well as footbridges.
  • Moreover, it is not often utilized in structures, although they could be utilized in particular conditions, for instance at the time that loads are transported off-center/eccentrically toward the beam axis.

Details of box girders:

  • It could include/cover a variety of spans from 25 m up till the biggest non suspended concrete decks constructed; in the range of 300 m.
  • Single box girders could even bear/carry decks up till 30 m broad.
  • With regard to the long span beams, above about 50 m, they are virtually the merely viable deck segment.
  • Beneath 30 m precast beams or vacated/voided slab decks are best suited whilst more than 50 m a one cell box setup is generally more cost-effective.
  • One-cell box girder cast-in-situ are utilized with regard to spans going from 40 m to 270 m.

Benefits of box girders:

  • Decrease the need with regard to support points
  • Possess excessive robustness as well as torsional firmness/stiffness that offer higher as well as improved appropriateness with regard to levelly bent bridges
  • Assure improved robustness
  • Need least safeguarding of straightforward protecting coverings for the reason that those possess least surface exposed as well as simply some peripheries

Drawbacks of box girders:

Among the major weights/burdens of box decks is that they are tough to get cast or assembled at site for the reason that of the separation of the base portion as well as the requirement to eradicate the inner shade. Whether the container should be figured in order that the entire cross-region/area may be immersed/thrown in a constant pour; or the cross-part/segment should be thrown in phases.

Construction of Box Girder Bridge