How exactly are bridges built in the middle? I understand that it could be while on a boat, but the workers would literally be moving around, no? I never thought about it before, but now I'm curious to know.
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1 A cantilever bridge is built from both sides to meet in the middle - with big hydraulic jacks to push the ends apart just enough to fit the last pieces.
2. Or a cantilever bridge can be built starting in the middle on a pier sunk down to bedrock and built so the side balance until it reaches the shore or short extensions from the shore.
3. Or a suspension bridge is built by making massive anchorages at the ends (usually on shore) and twin towers are built nearer shore in the water to go down to bedrock, then in one of several ways (including just climbing up the tower with a light cord and rowing the end of the cord to the other tower) heavier and heavier lines are run from one anchorage, up over the towers, to the other anchorage until the many wires in the support cables are bound - the support lines are added and the bridge sections either lifted up from barges (most common) or built in place from the shore if water conditions limit access from below.
2. Or a cantilever bridge can be built starting in the middle on a pier sunk down to bedrock and built so the side balance until it reaches the shore or short extensions from the shore.
3. Or a suspension bridge is built by making massive anchorages at the ends (usually on shore) and twin towers are built nearer shore in the water to go down to bedrock, then in one of several ways (including just climbing up the tower with a light cord and rowing the end of the cord to the other tower) heavier and heavier lines are run from one anchorage, up over the towers, to the other anchorage until the many wires in the support cables are bound - the support lines are added and the bridge sections either lifted up from barges (most common) or built in place from the shore if water conditions limit access from below.
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Depends on the type of bridge.
A girder or similar span, the span is built somewhere else and floated into place.
A suspension bridge, thin cables are ferried across by boat or helicopter, then more cables are wound on those by a special machine. Then the rest of the bridge is suspended from cables from those suspension cables.
Other bridges use other methods.
A girder or similar span, the span is built somewhere else and floated into place.
A suspension bridge, thin cables are ferried across by boat or helicopter, then more cables are wound on those by a special machine. Then the rest of the bridge is suspended from cables from those suspension cables.
Other bridges use other methods.