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ANCHORAGES
The anchorage is fundamental to the stability of a suspension bridge, as all the load in the cable must be transferred to a fixed anchorage (a. few small bridges with selfanchorages similar to cable-stayed bridges have been used). There are commonly three types:
1. Rock anchors.
2. Tunnel anchorage.
3. Gravity anchorage.
Rock anchorages simply involve drilling into the rock and grouting in large bolttype anchors to which the strands are subsequently attached. Where suitable rock is available, a U-tunnel can be constructed and the two cables joined to form a loop. However, the gravity anchorage has proved to be most popular with designers. The basic arrangement consists of looped over strand shoes attached to anchor bolts located in the concrete. The cable forces are thus resisted by a combination of overburden, dead weight and bearing friction.
The anchorage is fundamental to the stability of a suspension bridge, as all the load in the cable must be transferred to a fixed anchorage (a. few small bridges with selfanchorages similar to cable-stayed bridges have been used). There are commonly three types:
1. Rock anchors.
2. Tunnel anchorage.
3. Gravity anchorage.
Rock anchorages simply involve drilling into the rock and grouting in large bolttype anchors to which the strands are subsequently attached. Where suitable rock is available, a U-tunnel can be constructed and the two cables joined to form a loop. However, the gravity anchorage has proved to be most popular with designers. The basic arrangement consists of looped over strand shoes attached to anchor bolts located in the concrete. The cable forces are thus resisted by a combination of overburden, dead weight and bearing friction.
CABLE WRAPPING
The hangers are given a final tightening whereafter the cable is wrapped in galvanised mild steel wire (3-4 mm diameter) to provide corrosion protection. The wrapping machine consists of two drums encircling the cable and the wire is unwound as the unit in winched along. Wrapping can be achieved from either end of the machine in order that wire may be brought tight against a hanger band. The drum should contain just enough wire to cover between two hanger bands and allow the drums to be slit apart to pass the bands. The whole unit is hung from the tramway support strands and travels at about 0.5 m/min. The final operation requires the catwalk and other strands to be dismantled, this is a very difficult and dangerous operation requiring the workmen to raise the mesh panels by hand and winch them to the deck below.
The hangers are given a final tightening whereafter the cable is wrapped in galvanised mild steel wire (3-4 mm diameter) to provide corrosion protection. The wrapping machine consists of two drums encircling the cable and the wire is unwound as the unit in winched along. Wrapping can be achieved from either end of the machine in order that wire may be brought tight against a hanger band. The drum should contain just enough wire to cover between two hanger bands and allow the drums to be slit apart to pass the bands. The whole unit is hung from the tramway support strands and travels at about 0.5 m/min. The final operation requires the catwalk and other strands to be dismantled, this is a very difficult and dangerous operation requiring the workmen to raise the mesh panels by hand and winch them to the deck below.
HANGERS
Hanger cables are clamped directly to the suspension cable with tightly bolted bands. The main cable wrapping only extends up to the bands as these are fixed prior to the wrapping operation.
Hanger cables are clamped directly to the suspension cable with tightly bolted bands. The main cable wrapping only extends up to the bands as these are fixed prior to the wrapping operation.
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