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Geek Culture / Bridge Physics for a 3D Bridge Building Program

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Neuro Fuzzy
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Posted: 19th Dec 2009 17:10
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I decided to join this thing at my school called "Science Olympiad", basically, we compete in a bunch of different events (with other schools in the county, then the state, then the country), doing sciency stuff.

I got signed up for the bridge building event. You have to build a ibridge (before the event) that can hold the most weight, while staying within the allowed dimensions. Since I've just done a bunch of Genetic Algorithm stuff, i really want to create a bridge that was created with a Genetic Algorithm. The problem is that before i can set up the genetic algorithm, i need to create a 3d bridge simulator, or find one that is open source. This poses a problem because i have no clue how to do this....

The bridge will be constructed out of wood, so there is no need for lots of complexity as far as building material goes. Also, if any part of the bridge breaks, the bridge's stability is compromised, and therefore it is disqualified. There is no need to simulate the breaking of anything.

I can't really find any articles on bridge physics. They're all about school lessons for bridge building, or other, similar stuff.

Can anyone help me make a 3D wooden bridge builder?

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Zotoaster
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Posted: 19th Dec 2009 17:17
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PhysX can deal with this kind of stuff, but I think for things like breaking materials etc, you're going to have to buy an NVidia PhysX card.

"everyone forgets a semi-colon sometimes." - Phaelax
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AndrewT
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Posted: 19th Dec 2009 17:32 Edited at: 19th Dec 2009 17:43
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Not sure if this is exactly what you're looking for, but it features a pretty complete toolset and a Load Test feature that will show various weights traveling over the bridge and color different parts based on the amount of stress they're under.

http://bridgecontest.usma.edu/download2007.htm

Screenshot of Test:



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Neuro Fuzzy
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Posted: 19th Dec 2009 20:24
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I'm looking to create something similar (but not nearly as advanced) as that program, but i can't use some commercial application like that, because i want to control it using a genetic algorithm.

Still, that looks like a really cool program.

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AndrewT
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Posted: 19th Dec 2009 21:59 Edited at: 19th Dec 2009 21:59
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Ahh, I see.

If you're serious about this, I suggest reading up a bit on mechanics--you can start here:

http://web.mit.edu/emech/dontindex-build/index.html

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Diggsey
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Posted: 20th Dec 2009 01:10 Edited at: 20th Dec 2009 01:11
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Just put a single piece of solid wood across the gap, as big as the allowed dimensions


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charger bandit
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Posted: 20th Dec 2009 09:04
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A big straight concrete road with 10 pillars beneath,that will hold anything.

A.K.A djmaster
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demons breath
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Posted: 20th Dec 2009 17:59
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I think his chances of making "A big straight concrete road with 10 pillars beneath" out of wood by himself in the allotted time are somewhat limited...

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charger bandit
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Posted: 20th Dec 2009 18:56
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Dude,how hard it is to take a plank and a 2 metre long 2x4 piece of wood and cut it up into parts then put everything together with nails???

A.K.A djmaster
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BiggAdd
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Posted: 20th Dec 2009 19:56 Edited at: 20th Dec 2009 20:07
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The best bet is to build a truss bridge. It may not look pretty but it will hold the weight no problem.

We used to build them out of thin cardboard, which would hold about 5KG easy.

Also make sure your joins are strong. You don't want your bridge collapsing simply because of bad joins. You will find wood is very good for building a bridge as its best when under compression and tension (Just like concrete), this is why making a truss bridge is a good idea, as the compression and tension of it's members are easy to calculate.

How do you know how much your bridge will hold? For this, you need to calculate how much each member can take under tension and compression before failure. Then when you calculate how much force each member takes after you have designed your bridge, you can see the max weight your bridge can take.

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