Difference between revisions of "3048: Suspension Bridge"
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| − | + | A suspension bridge works by exploiting the strength in tension of a cable, or series of links, in what is ''usually'' described as a {[w|catenary}} curve (but see later) suspended between towers or other elevated positions and firmly anchored to the ground at either end. Such a cable, or parallel cables, can span a large gap, across which an arch (with compressive forces) or cantilever (with compression below and tension above) bridge structure would be more difficult. The slung droop of the connection, and various other issues (the susceptibility to resonance from moving loads, as well as the sheer impracticality of travelling along this link) means that the surface of the usual road (or footway) itself is suspended from this cable by vertical (and perhaps diagonal) suspending stringers of suitable lengths to maintain a more level track. This usually means that the greatest clearance beneath the traversable part of the bridge is not far below the middle of the main curve of the cable, which is often now a more a parabolic shape, due to the weight of the road and the large number of vertical cables required. | |
| − | A suspension bridge works by exploiting the | ||
| − | Randall suggests 'improving' the suspension bridge by having ''just'' the catenary curve, needing much less structure, and giving an increased clearance for anything passing beneath (in this case, a tall-masted sailboat) if they pass closer to the supporting towers. This, of course, means that the traffic can ''only'' cross upon the cables themselves, in a way that is not explained at all by this side-section view. Due to the steep nature of the way the cable must pass over the supports, this produces a steep gradiant up to and then down from the tower which sends traffic temporarily onto a free ballistic trajectory, assuming it has enough speed. This is classed as "fun jumps", {{w|Bug_(engineering)#"It's_not_a_bug,_it's_a_feature"|as if it is how bridges ''should'' work}}. This would likely inflict damage on the car, and might result in | + | Randall suggests 'improving' the suspension bridge by having ''just'' the catenary curve, needing much less structure, and giving an increased clearance for anything passing beneath (in this case, a tall-masted sailboat) if they pass closer to the supporting towers. This, of course, means that the traffic can ''only'' cross upon the cables themselves, in a way that is not explained at all by this side-section view. Due to the steep nature of the way the cable must pass over the supports, this produces a steep gradiant up to and then down from the tower which sends traffic temporarily onto a free ballistic trajectory, assuming it has enough speed. This is classed as "fun jumps", {{w|Bug_(engineering)#"It's_not_a_bug,_it's_a_feature"|as if it is how bridges ''should'' work}}. This would likely inflict damage on the car, and might result in unfortunate accidents.{{cn}} |
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==Transcript== | ==Transcript== | ||
Revision as of 03:48, 8 February 2025
| Suspension Bridge |
 Title text: As a first step, they can put in a secondary deck, to help drivers try it out and find out how fun the jumps are. After a while no one will use the old flat deck and they can remove it. |
Explanation
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This is one of 53 incomplete explanations: Created by a BOT JUMPING ON A BRIDGE - Please change this comment when editing this page. Do NOT delete this tag too soon. If you can fix this issue, edit the page! |
A suspension bridge works by exploiting the strength in tension of a cable, or series of links, in what is usually described as a {[w|catenary}} curve (but see later) suspended between towers or other elevated positions and firmly anchored to the ground at either end. Such a cable, or parallel cables, can span a large gap, across which an arch (with compressive forces) or cantilever (with compression below and tension above) bridge structure would be more difficult. The slung droop of the connection, and various other issues (the susceptibility to resonance from moving loads, as well as the sheer impracticality of travelling along this link) means that the surface of the usual road (or footway) itself is suspended from this cable by vertical (and perhaps diagonal) suspending stringers of suitable lengths to maintain a more level track. This usually means that the greatest clearance beneath the traversable part of the bridge is not far below the middle of the main curve of the cable, which is often now a more a parabolic shape, due to the weight of the road and the large number of vertical cables required.
Randall suggests 'improving' the suspension bridge by having just the catenary curve, needing much less structure, and giving an increased clearance for anything passing beneath (in this case, a tall-masted sailboat) if they pass closer to the supporting towers. This, of course, means that the traffic can only cross upon the cables themselves, in a way that is not explained at all by this side-section view. Due to the steep nature of the way the cable must pass over the supports, this produces a steep gradiant up to and then down from the tower which sends traffic temporarily onto a free ballistic trajectory, assuming it has enough speed. This is classed as "fun jumps", as if it is how bridges should work. This would likely inflict damage on the car, and might result in unfortunate accidents.[citation needed]
Transcript
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This is one of 28 incomplete transcripts: Do NOT delete this tag too soon. If you can fix this issue, edit the page! |
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What if a car doing one of the fun jumps lands on a car that didn't do a fun jump? Should we mandate that every car does a fun jump for this reason (and yay, fun jump!)? 198.41.227.115 22:08, 7 February 2025 (UTC)
- Radar speed management, vehicles are only let on the bridge if their expected land point is between the vehicles around them. 172.68.55.80 22:48, 7 February 2025 (UTC)
- Carrot/stick question. If they do a jump, they get their toll refunded on the far side of the bridge. Maybe give them double refund if they do a flip. 172.69.246.135 04:07, 8 February 2025 (UTC)
- The same would happen as on a normal road. If you drive faster than the car in front of you and do not break you will run into it. Only difference here is that you cannot break after jumping so if the one in front of you did make a small jump and then hit the brakes you could hit him. But if you drive very fast up towards a car on a normal road, and they hit the brakes, you will likely also hit them. Even though you do have a chance to brake as opposed to after a jump. So I do not see this as any different than a regular road. Only problem is someone will find it so fun to drive fast towards the top, they might forget to think about safety. But that is already a real problem on normal roads... You cannot stop someone from entering the bridge based on their speed before thet enter the bridge... So the radar comment makes no sense to me!? --Kynde (talk) 08:20, 9 February 2025 (UTC)
- Carrot/stick question. If they do a jump, they get their toll refunded on the far side of the bridge. Maybe give them double refund if they do a flip. 172.69.246.135 04:07, 8 February 2025 (UTC)
Do suspension bridges still work when built this way? Those pilings look much easier to sway to me. Maybe they are just buried a little more securely. 172.68.55.80 22:48, 7 February 2025 (UTC)
- Yep! With "classic" suspension bridges (like the Golden Gate Bridge), there is no fixed connection between the deck and the towers. With differring loads and temperatures the deck can move up and down about 30cm at tower level (and almost 2 netres at midpoint). Some modern bridges do ise a fixed connection or hinge between deck and tower. IIVQ (talk) 12:58, 8 February 2025 (UTC)
This looks a lot like a stressed ribbon bridge. 172.69.64.132 22:59, 7 February 2025 (UTC)
This exact proposal, the 'dangling road', is actually The Meta in Poly Bridge 2. Poly Bridge 3 tried to tweak the numbers to make this strat less effective, but a variant of it continues to persist to this day. (This probably goes in the trivia section, because it seems like Randall came to this concept from first principles.) 172.71.151.65 01:07, 8 February 2025 (UTC)
- I came to the comment section to see if somebody already said that. The other thing I would have said is I wonder if RCE reads XKCD… if not, I think someone should ask him to do a blind reaction to this comic. I'd love to see his response :) -- Angel (talk) 19:18, 8 February 2025 (UTC)
It's funny to me, there's a level in Jak II for the PS2 that's literally just this idea: for whatever reason the city's central palace is held up by five suspension bridge-esque wires, and one level has you crawling along wire #4 to get inside the palace (the catch? The wires are covered in security robots) 172.71.159.7 01:54, 8 February 2025 (UTC)
I like the fact that vehicles are clearly on flexible cables, not some rigid material formed into a catenary shape. There's a truck between the two towers that is visibly depressing the cable it's riding. Nitpicking (talk) 03:57, 8 February 2025 (UTC)
- Happy happy joy joy. No dogs allowed on this bridge. 162.158.42.87 04:35, 8 February 2025 (UTC)
If you add a downward pressure to a rope that's significantly stronger than it's normal tension, you end up with a parabola 162.158.137.212 17:47, 8 February 2025 (UTC)
Related: The Wooden bridge Tatzlwurm" in Essing Germany by Richard Johann Dietrich: [1]. Maybe it could be included in the explanation. Rps (talk) 20:46, 8 February 2025 (UTC)
- Not sure I think this is really related. It is also possible as opposed to Randall's proposal here ;-) --Kynde (talk) 08:20, 9 February 2025 (UTC)
- Another example is the Karlssteg in Freiburg im Breisgau, Germany. [2] 108.162.241.160 (talk) 15:46, 10 February 2025 (please sign your comments with ~~~~)
It would seem that Randall has re-invented the https://en.wikipedia.org/wiki/Simple_suspension_bridge 172.68.54.207 (talk) 15:17, 9 February 2025 (please sign your comments with ~~~~)
- More so the mostly 'simple'-derived Stressed ribbon bridge. Unless you consider that development more a version of the non-simple type, with the descenders degenerated completely into the deck structure through high tension, i.e. a step beyond the "structure hiding" levels of other low-profioe suspension bridges. 172.71.178.78 15:37, 9 February 2025 (UTC)
I seem to recall a bridge on the overseas highway (Florida Keys) that was originally an arch bridge above a grade-level rail line. When they wanted to "upgrade" the route for cars, cars wouldn't fit into the narrow rail bridge, so they planked up and over the arches, and it was apparently quite a scary drive. I can't seem to locate it via google, although I'm sure I recall seeing it on my drive to key west about 20 years ago. I suspect it's gone now. RandalSchwartz (talk) 20:34, 9 February 2025 (UTC)
- Ahh, it was the Bahia Honda Railroad Bridge. A few pictures of the structure (mostly torn down now) can be seen here. RandalSchwartz (talk) 22:55, 9 February 2025 (UTC)
- Find it on Google Earth at 24°39.3142'N 81°17.5182'W. Mostly still there as of image date (2023, if I read correctly). 172.71.146.78 15:43, 10 February 2025 (UTC)
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- Find it on Google Earth at 24°39.3142'N 81°17.5182'W. Mostly still there as of image date (2023, if I read correctly). 172.71.146.78 15:43, 10 February 2025 (UTC)
