eli5: How did people build bridges over deep and/or dangerous water if they didn’t have the equipment to go under water?
In: 22
Depends on how big the bridge is and what type you need.
A suspension bridge can be built by pulling ropes across the water. You don’t even need to pull the main ropes across first, you can pull a lighter rope across then use that to pull the larger rope or join multiple smaller ropes together to make the large bridge.
You can also [launch](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjl57f4zYD-AhW9m1YBHQ8mBCcQwqsBegQIChAE&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DNgGL5-3dkVw&usg=AOvVaw32Ili4AiyW2cTvgYgj8BGY) a bridge, that is, build it on land then push it out over the water. This is still an option for building bridges, sometimes by building a segment, launching it out then building another segment and repeating the process. You can do this with piers in the middle or as a single span.
You can lift the bridge out into place – this may need larger lifting gear but it can also be done in parts and then assembled in place. You can also [use a crane on a boat](https://www.engineeringnz.org/programmes/heritage/heritage-records/auckland-harbour-bridge/) to float the bridge out then lift it up.
All of the above can be done to completely bridge over the deep water if you can make the bridge long enough between supports. If you can’t, then you’ll need to put supports in. A coffer dam is a fairly common way of doing this which I see has been explained already. You can also use a drilling rig to drill a pier into the ground without needing to dive down but both of these methods wouldn’t be achievable in very deep water without reasonably modern technology (post industrial revolution at least). Before that, they were limited in where they could build bridge piers to areas where they could build dams deep enough or where they could drive piles into the riverbed from the surface
Depends on how big the bridge is and what type you need.
A suspension bridge can be built by pulling ropes across the water. You don’t even need to pull the main ropes across first, you can pull a lighter rope across then use that to pull the larger rope or join multiple smaller ropes together to make the large bridge.
You can also [launch](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjl57f4zYD-AhW9m1YBHQ8mBCcQwqsBegQIChAE&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DNgGL5-3dkVw&usg=AOvVaw32Ili4AiyW2cTvgYgj8BGY) a bridge, that is, build it on land then push it out over the water. This is still an option for building bridges, sometimes by building a segment, launching it out then building another segment and repeating the process. You can do this with piers in the middle or as a single span.
You can lift the bridge out into place – this may need larger lifting gear but it can also be done in parts and then assembled in place. You can also [use a crane on a boat](https://www.engineeringnz.org/programmes/heritage/heritage-records/auckland-harbour-bridge/) to float the bridge out then lift it up.
All of the above can be done to completely bridge over the deep water if you can make the bridge long enough between supports. If you can’t, then you’ll need to put supports in. A coffer dam is a fairly common way of doing this which I see has been explained already. You can also use a drilling rig to drill a pier into the ground without needing to dive down but both of these methods wouldn’t be achievable in very deep water without reasonably modern technology (post industrial revolution at least). Before that, they were limited in where they could build bridge piers to areas where they could build dams deep enough or where they could drive piles into the riverbed from the surface
To add to the previous explanations – here’s an animation how a 13-meter tall bridge in Prague was built in roughly 60 years (Charle’s Bridge). It’s an official reconstruction of the local historic society how it was built. Should answer some questions. IIRC it started 1348 and was opened 1407. (not sure about it and too lazy to check it)
[https://www.youtube.com/watch?v=nJgD6gyi0Wk](https://www.youtube.com/watch?v=nJgD6gyi0Wk)
Edit> 1357 – 1402, meeting was less important so I actually checked it 😀
To add to the previous explanations – here’s an animation how a 13-meter tall bridge in Prague was built in roughly 60 years (Charle’s Bridge). It’s an official reconstruction of the local historic society how it was built. Should answer some questions. IIRC it started 1348 and was opened 1407. (not sure about it and too lazy to check it)
[https://www.youtube.com/watch?v=nJgD6gyi0Wk](https://www.youtube.com/watch?v=nJgD6gyi0Wk)
Edit> 1357 – 1402, meeting was less important so I actually checked it 😀
I remember an architect saying:
The bridge is 20% a bridge and 80% how to put it there.
There are several ways, but can be grouped in:
Remove the water, literally temporarily reroute the river.
Redirect the water: build a dam around the future pillar location, drain the spot.
The floor is lava: rework the ground on the two sides to make it firm enough to place massive equipment, from which you launch the premade bridge over the gap.
The floor is lava but old school: you build a lightweight wooden/whatever bridge from the shore into the river, join with the same structure coming from the other side. Use this structure as a platform on which you build the bridge.
The pointy stick: you stick giant sticks in the water and put the bridge over those sticks.
The suspended thing: you build a cablecar-like thing, from which you deploy wire after wire until you have a “golden gate”thing. Then from those wires you work your way down to build the road part.
Ice is your friend: stick pipes in the water, run coolant in the pipes and create an ice wall. It can be done to help in any of the above methods, where applicable. Even to freeze the terrain to prevent water to filter into a hole/excavation/whatever.
In all cases, the problem is not being under water, most construction hate water or hate being jointed in water. So even if you are the chief of the scuba planet with millions of scuba soldiers, you probably want the structure to be built in a dry environment. Then you can flood part of it, but only after it’s assembled or cured.
The above methods can be mixed in many ways.
They damned and drained the water.
The equipment to go under water is a lot older than you think too. Check out diving bells for some terrifying nightmare fuel.
I remember an architect saying:
The bridge is 20% a bridge and 80% how to put it there.
There are several ways, but can be grouped in:
Remove the water, literally temporarily reroute the river.
Redirect the water: build a dam around the future pillar location, drain the spot.
The floor is lava: rework the ground on the two sides to make it firm enough to place massive equipment, from which you launch the premade bridge over the gap.
The floor is lava but old school: you build a lightweight wooden/whatever bridge from the shore into the river, join with the same structure coming from the other side. Use this structure as a platform on which you build the bridge.
The pointy stick: you stick giant sticks in the water and put the bridge over those sticks.
The suspended thing: you build a cablecar-like thing, from which you deploy wire after wire until you have a “golden gate”thing. Then from those wires you work your way down to build the road part.
Ice is your friend: stick pipes in the water, run coolant in the pipes and create an ice wall. It can be done to help in any of the above methods, where applicable. Even to freeze the terrain to prevent water to filter into a hole/excavation/whatever.
In all cases, the problem is not being under water, most construction hate water or hate being jointed in water. So even if you are the chief of the scuba planet with millions of scuba soldiers, you probably want the structure to be built in a dry environment. Then you can flood part of it, but only after it’s assembled or cured.
The above methods can be mixed in many ways.
I remember an architect saying:
The bridge is 20% a bridge and 80% how to put it there.
There are several ways, but can be grouped in:
Remove the water, literally temporarily reroute the river.
Redirect the water: build a dam around the future pillar location, drain the spot.
The floor is lava: rework the ground on the two sides to make it firm enough to place massive equipment, from which you launch the premade bridge over the gap.
The floor is lava but old school: you build a lightweight wooden/whatever bridge from the shore into the river, join with the same structure coming from the other side. Use this structure as a platform on which you build the bridge.
The pointy stick: you stick giant sticks in the water and put the bridge over those sticks.
The suspended thing: you build a cablecar-like thing, from which you deploy wire after wire until you have a “golden gate”thing. Then from those wires you work your way down to build the road part.
Ice is your friend: stick pipes in the water, run coolant in the pipes and create an ice wall. It can be done to help in any of the above methods, where applicable. Even to freeze the terrain to prevent water to filter into a hole/excavation/whatever.
In all cases, the problem is not being under water, most construction hate water or hate being jointed in water. So even if you are the chief of the scuba planet with millions of scuba soldiers, you probably want the structure to be built in a dry environment. Then you can flood part of it, but only after it’s assembled or cured.
The above methods can be mixed in many ways.
They damned and drained the water.
The equipment to go under water is a lot older than you think too. Check out diving bells for some terrifying nightmare fuel.
They damned and drained the water.
The equipment to go under water is a lot older than you think too. Check out diving bells for some terrifying nightmare fuel.
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