General Information

Figure 1 shows a suspension bridge that is used by motorcycles, bicycles and pedestrians.

Suspension bridge.
 Suspension bridge over a river
Type Single-span suspension bridge
Main span ≅ 70 m
Deck width ≅ 1.5 m
Deck width to main span ratio ≅ 1:46
Pylon Reinforced concrete
Girder Timber transverse beam

Hanger Cable to Timber Girder Connection

Figure 2 shows a schematic cross-section of the bridge.

Cross-section.
Cross-section of a wooden suspension bridge

A single hanger cable runs from main cable 1 to main cable 2 via the girder bottom side. The hanger cable passes through the girder through two vertical holes. The forces are transferred by direct (cable to girder) contact. Figure 3 shows a hanger cable to girder connection viewed from below.

Hanger cable to girder connection (1).
Hanger cable to timber girder connection viewed from below

There is an offset between the vertical hole and the hanger cable bent region, and a longitudinal crack that extends from the girder's end to the hanger cable bent region is noticeable. The timber fiber direction is indicated by the double white arrow. A further connection viewed from the side is shown in figure 4.

Hanger cable to girder connection (2).
Hanger cable to timber girder connection viewed from the side

A similar crack configuration and hanger cable offset are noticeable; a stringer and a deck plank are touched by the hanger cable.

  • What are some possible reasons for the offset between the vertical hole and the hanger cable?
    What are the main consequences?
  • Figure 5 shows a further hanger cable to girder connection.

    Hanger cable to girder connection (3).
    Hanger cable to timber girder connection

    An additional cable is connected to the hanger cable (over the deck region) by U-bolt clamps, bent around the girder, and fixed with two U-bolt clamps. Free space between the additional cable and the girder is noticeable.

  • What is the purpose of the additional cable?
  • Hanger Cables

    Figure 6 shows a main span sector.

    Main span.
    Main span sector with unequal hanger cables

    Noticeable are taut, slack, and twisted hanger cables, irregular spacing, different numbers of U-bolt clamps, and different main cable connections (e.g., with and without a frame plate).

  • What are some possible reasons for the above shown hanger cables?
  • Deck Deformation

    Figure 7 shows a main span sector.

    Main span.
    Deck deformation of a main span sector

    Deck deformation is noticeable.

  • What are some possible deformation causes?