The corrugated steel web PC box girder bridge is a composite structure composed of concrete top and bottom slabs and corrugated steel webs. It can be regarded as a new structure derived from ordinary prestressed concrete box girder bridges, with similar overall structural mechanical characteristics to that of the ordinary concrete box girder bridge.

Years of engineering construction practice have shown that there are two main engineering diseases in ordinary long-span prestressed concrete continuous rigid frame and continuous girder bridges:

（1）cracking of the concrete web of the box girder;

（2）continuous deflection in the mid-span of the main girder.

The main reason is that the shear and tensile strength of the concrete web is insufficient, and constantly thickening the web will lead to excessive weight of the structure, unreasonable force bearing and uneconomical. The long-span corrugated steel web PC box girder bridge improves these two drawbacks of ordinary long-span prestressed concrete box girder bridges by using corrugated steel webs to replace the traditional concrete webs.

Asynchronous Form Traveler

Unique structural characteristics

(1) By using corrugated steel webs instead of concrete webs, the self-weight of the structure can be reduced by up to 20%. However, for long-span continuous girder bridges, due to the setting of the lined concrete section on the inner side of the corrugated steel web near the main piers to prevent the instability and buckling of the steel plate, the reduction of the overall structure's self-weight is only about 10%; but the reduced part is concentrated in the mid-span, so the reduction effect on the bending moment of the main girder is very obvious. Another advantage of the reduction of the self-weight of the superstructure is that it can reduce the engineering quantity of the substructure and reduce the cost.

(2) Due to the very small longitudinal expansion and contraction stiffness of the corrugated steel web, which can be ignored, the force bearing of the corrugated steel web PC box girder is clear: the axial force is basically borne by the concrete top and bottom slabs, and the shear force is basically borne by the corrugated steel web (about 87%). Due to the absence of the constraint of the web, the efficiency of prestressing the top and bottom slabs is significantly improved, and the shrinkage and creep deformation of the top and bottom slabs will not transfer to the web, thereby avoiding the common problem of inclined cracking of the web of traditional concrete box girders and further reducing the mid-span deflection.

(3) For long-span corrugated steel web PC box girder bridges, several external prestressing tendons are generally set in the box to improve the flexural and shear bearing capacity of the structure and help reduce the mid-span deflection.

(4) Compared with ordinary prestressed concrete box girders, the torsional stiffness of the cross-section of corrugated steel web PC box girders decreases by about 60%. For long-span corrugated steel web PC girder bridges, this adverse effect can be solved by setting several transverse diaphragms in the box, and some of the transverse diaphragms are also used as the steering mechanism for the external tendons.

(5) Due to the lightweight structure of the corrugated steel web PC box girder, the segments can be longer when using the cantilever casting construction method; moreover, after using the steel web, the amount of reinforcement binding and concrete pouring is reduced, thereby effectively shortening the construction period. In addition, using the steel web as the load-bearing component for the cantilever casting construction (referred to as the "RW construction method") (Figure 1) can significantly reduce the size and weight of the hanging basket. After the lightweight form traveler is equipped with a designed walking device, it can walk freely on the top of the steel web, making the construction more convenient and the construction period shorter.

Figure 1:Schematic Diagram of the RW Construction Method for Cantilever Construction of Corrugated Steel Web PC Box Girder Bridge  

To Sum Up

The corrugated steel web PC box girder bridge has solved many problems of ordinary long-span prestressed concrete box girder bridges and shows significant advantages. In every bridge construction project, it is recommended that engineers fully consider the application possibility of this structure to promote the development and progress of the bridge construction industry.