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Equilateral triangle bridge

One big one.
  [vote for,

Equilateral triangles are used in bridges all the time - but generally a series of little ones. I propose that the bridge be two huge equilateral triangles. The big ones would be filled with little ones to convey the weight from the bottom part up to the two sides of the triangle.

This would be as effective as a bunch of small ones in regard to getting people across. But visually it would be much more dramatic.

bungston, Jul 02 2013

Not equilaterals per se http://www.thairive...0_1_9_img1_1744.jpg
[not_morrison_rm, Jul 02 2013]

Triangles http://www.google.c...0,i:235&tx=86&ty=93
Here is one big one filled with little ones. Maybe those little ones could be filled with littler ones. [bungston, Jul 02 2013]

Triangle bridge http://www.google.c...,i:253&tx=121&ty=61
But it has right triangles, not equilateral. [scad mientist, Jul 03 2013]

Portland Bridges http://www.bizave.com/portland/bridges/
They did not think the 1970 one was pretty enough, if I understand right. [bungston, Jul 06 2013]

http://en.wikipedia...muel_Beckett_Bridge For [nrm] [pocmloc, Jul 07 2013]

Zakim Bridge, Boston MA http://www.portland...boston_Zakim_BR.jpg
[xandram, Jul 08 2013]

Sierpinski triangle https://en.wikipedi...Sierpinski_triangle
yeah! [bungston, Oct 07 2015]


       I'm having a hard time picturing this. Are the bridge openings triangular or is the suspension triangular? Horizontal or vertical triangles? Are the little ones inverting or in-line with the big ones?   

       Well, the same could be said for squares, circles, or dodecahedrons. Once you understand how a truss works, patterns emerge - but it's not as simple as saying "triangles are good".   

       ...And once you're up to the scale of a bridge, it's normally all curves anyway, except for very old ones.   

       //The big ones would be filled with little ones to convey the weight from the bottom part up to the two sides of the triangle.//   

       It's like you kind-of know how a bridge works, but only sort-of.
Custardguts, Jul 02 2013

       "Only sort-of" is my watchword!   

       No curves. No stuff hanging down. Nothing in the middle but a pointy point. Two big triangles. Car starts on one side of the triangle and drives across to the other.
bungston, Jul 02 2013

       One big triangle is pretty but pointless. Putting a little triangle upside-down in the middle of it (making 4 triangles) is better... but the top little triangle still doesn't do anything. Take the ^ away making sure to leave the - ('cuz that's what's doing all the work) and... you have what a small bridge usually looks like.
FlyingToaster, Jul 02 2013

       Congratulations, you just invented a simple truss.
Custardguts, Jul 03 2013

       I think it would be more interesting without a uniform fill of the triangle. Specifically, I think a Sierpinski triangle would be very nice.   

       As [FlyingToaster] said, this isn't a huge departure from standard outdated truss bridge design like the one that just recently collapsed here in Washington State, but I will say that with a Sierpinski triangle, leaving the point on top ought to allow using a smaller beams because each beam is suported by a smaller Sierpinski triangle which will help prevent buckling (at least in one plane).   

       This makes me wonder if there are any structural benefits to a Sierpinski triangle used as a truss.
scad mientist, Jul 03 2013

       //outdated// in what respect ? Equilateral triangles are the best bang for the buck. Squares suck: you have to brace them crossways.
FlyingToaster, Jul 03 2013

       Truss [CustardGuts] to get all architectural on us!
zen_tom, Jul 03 2013

       Probably not a good idea, we all remember what happened to the triangular aquaduct project near Bermuda...
not_morrison_rm, Jul 03 2013

       The triangular truss is largely outdated because they are generally not necessary. For shorter bridges, simple beam bridges or box girder bridges are sufficient, for longer bridges, arch (and yes, some are arch truss, but they aren't triangular) are stronger for less material, and for the longest bridges either suspension or cable stay give you the best strength for cost.   

       The one exception I've seen recently is prefab pedestrian bridges where the truss forms the hand rail, since the superstructure serves the dual purpose.
MechE, Jul 03 2013

       If you used one of those fractal triangles...you know, the ones where a smaller tringle is added along the length of the previous triangle....you would never finish the bridge...it would be permanent employment....until down to nano-scales, at least.   

       Edit: I was going to edot "tringle" but decided to let it stand.   

       Edit 2: "edot"....damned Damsung keyboard...etc...
Ling, Jul 04 2013

       And you might get your pinsky Sier’d.
pocmloc, Jul 04 2013

       I started pondering this after being told that the Portlanders protested a large bridge across their river because it was too ugly. Sturdy, cheap, very functional, but ugly. So if in bridges, aesthetics is worth some expense why not a big triangle? Agreed the top bit is just decorative but it comes cheap and offers some fearful symmetry.
bungston, Jul 06 2013

       now all we need is the rest of the huge instruments for the world's largest orchestra.   

       However, suspect if all assembled at one point it might just change the axis of orbit.
not_morrison_rm, Jul 07 2013

       Honestly, a central pier cable stay bridge approaches this in shape, but not in function (the cables aren't quite straight lines, but they're close). Just design one where the outermost cables are 30 degrees off vertical, and you'll get close enough.
MechE, Jul 08 2013

       Yeah, just adjust the caternary tension until it approximates a straight line.   

       ..might require some as-yet undiscovered supermaterial for the stays.
Custardguts, Jul 08 2013

       It's technically impossible to pull a cable with a horizontal run under gravity loading into a perfectly straight line. Existing cable-stayed bridges approach close enough if all you care about is appearances.
MechE, Jul 08 2013

       //It's technically impossible to pull a cable with a horizontal run under gravity loading into a perfectly straight line.   

       Given enough supporting sticks, or ants all holding onto each other's hindlegs, I'm sure a it can be done.
not_morrison_rm, Jul 08 2013

       Cables, schmables. You can't swing a cat without hitting a bridge with cables. This is for a bridge to make a city proud. The two overlapping triangles would be the logo for the city. Kind of like the St Louis arch, but good for something.
bungston, Jul 08 2013

       //It's technically impossible to pull a cable with a horizontal run under gravity loading into a perfectly straight line//   

       Unless you pluck it...albeit temporarily.
Ling, Jul 08 2013

       I have to think the architects will not readily give up pretension.
bungston, Jul 09 2013

       And a lot of modern buildings (residential) don't have any arches, so why do we still call them Architects?
not_morrison_rm, Jul 09 2013

       I think the root is the same as 'archive': a place for storing things.
FlyingToaster, Jul 09 2013

       Archi = chief, techton = builder.
spidermother, Jul 09 2013

       Waste of material. The Bigger bridge, the more waste.   

       Unless you put in an observation deck like the St. Louis Arch, don't see any practical point to it.
popbottle, Jul 12 2013

       The wasteful top part is Art. High art, even.
bungston, Jul 13 2013

       I saw a Sierpinski triangle today and thought - "yeah! that is what the bridge needs to have". I see scad thought of this immediately and posted the anno but I feel good about that too. It is not the first time.   

       The trick to finsihing the bridge would be that the increased geometry would condense: the overall bridge would have 4 levels, then the section to the right 5, smaller subsection 6 and on down. The section where the triangles get really detailed comprise the wall of the visitors center / view deck. A lens is set up so you can view the smallest levels of detail.   

       I can see the city merch with the triangle, just like St Louis does with the arch.
bungston, Oct 07 2015


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