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from the shape-of-things^Wbridges-to-come dept.
Arthur T Knackerbracket has found the following story:
Newly identified bridge forms could enable significantly longer bridge spans to be achieved in the future, potentially making a crossing over the Strait of Gibraltar, from the Iberian Peninsula to Morocco, feasible.
[...] A bridge's span is the distance of suspended roadway between towers, with the current world record standing at just under 2km. The most popular form for long spans is the suspension bridge form, as used for the Humber Bridge, though the cable-stayed bridge form, where cables directly connect the tower to the roadway -- such as used in the recently constructed Queensferry Crossing in Scotland -- is becoming increasingly popular.
As bridge spans become longer, a rapidly growing proportion of the structure is needed just to carry the bridge's own weight, rather than the traffic crossing it. This can create a vicious cycle: a relatively small increase in span requires use of significantly more material, leading to a heavier structure that requires yet more material to support it. This also sets a limit on how long a bridge span can be; beyond this limit a bridge simply cannot carry its own weight.
[...] Professor Matthew Gilbert from the University of Sheffield, who led the research, said: "The suspension bridge has been around for hundreds of years and while we've been able to build longer spans through incremental improvements, we've never stopped to look to see if it's actually the best form to use. Our research has shown that more structurally efficient forms do exist, which might open the door to significantly longer bridge spans in the future."
[...] The mathematically optimal designs contain regions which resemble a bicycle wheel, with multiple 'spokes' in place of a single tower. But these would be very difficult to build in practice at large scale. The team therefore replaced these with split towers comprising just two or three 'spokes' as a compromise that retains most of the benefit of the optimal designs, while being a little easier to construct.
For a 5km span, which is likely to be required to build the 14km Strait of Gibraltar crossing, a traditional suspension bridge design would require far more material, making it at least 73 per cent heavier than the optimal design. In contrast, the proposed two- and three-spoke designs would be just 12 and 6 percent heavier, making them potentially much more economical to build.
[...] The team emphasise that their research is just the first step, and that the ideas cannot be developed immediately for construction of a mega span bridge. The current model considers only gravity loads and does not yet consider dynamic forces arising from traffic or wind loading. Further work is also required to address construction and maintenance issues.
-- submitted from IRC
Journal Reference:
Helen E. Fairclough, Matthew Gilbert, Aleksey V. Pichugin, Andy Tyas, Ian Firth. Theoretically optimal forms for very long-span bridges under gravity loading. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science, 2018; 474 (2217): 20170726 DOI: 10.1098/rspa.2017.0726
(Score: 0, Informative) by Anonymous Coward on Tuesday September 25 2018, @03:05AM (3 children)
And you don't typically see elevators that are that long, except for the freight elevator and perhaps a penthouse elevator by an extremely rich individual who can afford to spend the money on the floor space it takes up. Aristarchus is a moron.
The practical limit on the height of elevators has to do with the number of trips that the elevator is expected to perform; especially during the the peak periods before and after work as well as during lunch time. Yes, it's possible to have a 70+ floor elevator, but it's not practical for anything other than the freight elevator, because in an office building, as few as 15 floors can wind up with a substantial wait when everybody is wanting to use them all at once. An elevator of 70 floors serving passengers would be crippled by the massive number of people using it.
This is the main reason why it is common for highrise buildings have one or more banks of express elevators allowing them to stack local elevators to service individual floors.
Even if you switch to a cableless system, you'd still be limited to a similar number of floors being serviced unless you have a system of elevators that can switch shafts or shift out of the way of each other due to congestion.
(Score: 2, Insightful) by aristarchus on Tuesday September 25 2018, @03:51AM (2 children)
Of course you realize, oh pugnacious AC, that you are involved in a not so subtle program of distraction? Next you will be telling us that it is possible to build a bridge to the top of the tallest building, blithely ignoring that nothing you are saying about elevators is relevant to the point I was making about Bridges Too Far. Nice try. You probably distracted khallow, . . . unless you are khallow! Not arguing in good faith? Checks out.
(Score: 0) by Anonymous Coward on Tuesday September 25 2018, @05:32AM (1 child)
Lose an argument, then suddenly realize the argument was off-topic.
Classic arse-tarchus.
(Score: 2, Insightful) by aristarchus on Tuesday September 25 2018, @06:18AM
Because the argument was off topic. Why do you think I threw in a structural limit to capitalism spin in there, you cretins of the cold war? Do you not realize that your thinking is not only invalid, (that is, your reasoning does not support the conclusions you admire, even if your premises and starting points are true), but your axioms are so far removed from reality that you could buy a Rainbow Bridge, with or without Thor, but probably with Unicorns, and Pedophilic Distributed Defense Unicorns. Snap out of it, you morons. Also, the first part of my name is from the greek, ἄριστος, meaning "the best". Your riff on it suggests certain proclivities. Are you not already over-extended enough? Is not your intellectual capital wasted in the defense of the same? At long last, AC, have you no shame?