General Information

Figure 1 shows a cable-stayed bridge that is used by motorcycles, bicycles and pedestrians.

Cable-stayed bridge.
Cable-stayed bridge over a river
Type Three-span cable-stayed bridge
Main span ≅ 50 m
Deck width ≅ 2 m
Girder Steel truss
Pylon Reinforced concrete (H-shaped)
Stay cable arrangement Fan (two cable planes)

Truss Girder

Figure 2 shows the bridge.

Cable-stayed bridge.
Curved truss of a cable-stayed bridge

The truss girder girder has a slightly curvature and an isosceles trapezoidal cross-section, as shown in figure 3.

Truss girder (shematic three-dimensional view).
Three-dimensional drawing of a truss girder

The truss in made of circular hollow profiles and consists of three upper chords, three bottom chords, diagonals, verticals, horizontal braces, and cross-braces. The upper base B ≅ 2 m, the bottom base b ≅ 1.4 m, and the height h ≅ 0.8 m. The truss consists of several units that are connected by bolted end-plates, as shown in figure 4.

Truss units connection (side view).
Connection between two truss units

The truss does not have diagonals in the connection region, and the field length l is shorter. Figure 5 shows the used truss girder and a braced twin I-girder as an alternative variant.

Truss girder and braced twin I-girder (shematic three-dimensional view).
Three-dimensional drawing of a truss girder and a braced twin I-girder
  • Is the truss girder chosen for structural efficiency reasons?
  • Stay Cable Bending

    Figure 6 shows a side span.

    Side span.
    Side span of a cable stayed bridge

    The girder anchorage region of stay cable 1, viewed from above, is shown in figure 7.

    Girder anchorage region (stay cable 1).
    Anchorage at the girder

    The girder anchorage is fixed (not hinged), and stay cable bending is noticeable.

  • What are some possible reasons for the above shown stay cable bending?
    What are the main consequences?