Concrete Beam Design

[Evlich]

Hello, I am working on a project to design a concrete beam that is 2in x 2in x 12in that will be able to hold the most weight. I have been searching the web for a while for any similar projects and all that I can't seem to find anything relatively simple (I am a high school student and I am doing this for a design course, not really an in depth physics course). I am just looking to have some general place to start my design with. Thanks a lot, any help is greatly appreciated.

~evlich

[aman]

If I had a 12 inch shaft that had to support a solid weight then I would put most of the concrete mass at the two sides of the shaft evenly divided to form a structure closest to a Roman arch but you did not say how the concrete would be anchored.

An arch is a very efficient design for distributing weight between two points next to 90 degree angles.

Just aman

[Evlich]

Here is the thing, the total thing can only be 2 in from base of the lowest part to the top of the highest part. If I do an arch, and that would probably be difficutl to make a form for, I would only be able to slope it a little and it would end up being very thin? It seems like that would make a difference, but would the arce itself be enough to overcome the lack of actual concrete, does that even affect it? Thanks a lot for your advice.

~evlich

[YT2095]

couldn`t you model the structure on the frame used in Cranes an then make that out of rebar, fortified with carbon fiber filliments, and then pour in your cement?

Just a thought

[Evlich]

This is a pretty simple project. We get sand concrete mix, coat hangers, and we can make the form from cargboard and ducttape.

[YT2095]

are you allowed to cut up the coat hangers and solder them (or braze), and are you allowed to heat treat them to make it more tensile?

Sounds like a fun project actualy

[atinymonkey]

If you work out requirements for a mould and build it, put in basic wire frame in the mold, you could then concentrate on the quality of concrete. Shredding the spare paper to make pulp (5 to 10% volume) and shaving spare coathanger to metal filings (0.5 to 2%), even shredding the spare duct tape (very small 7mm or less for 2 to 3 %) should help to produce a high strength mortar. Mix in sand and 2-5mm aggregate to finish. Add concrete at the mix rate and mix well. If you see any superglue around chuck it in, it should replace the plasticizer you would normally use.

 

The structure itself is second to the quality of the structure. Mix the concrete poorly and it will just crumble or crack (well it will anyhow in your tests, but never mind!).

 

Like Aman says, a low flat arch would be best. Not a huge arch, with your limits, but a curved beam would really improve strength. Just build the straight mould 3cm short of 2 inches and bend it slightly to make a curve and fit in the 2 inch box.

[blike]

Haha, i suppose the aim of the project is that you cut the coathanger into segments, and then run several of them through the middle of the concrete, mimicing steel-reinforcement.

[blike]

or listen to atinymonkey, who knows infinitely more about that than I

[YT2095]

there`s only really 3 main factors to it in a lab test I should imagine, Compression, Expansion and Torsion forces to deal with.

if you know what they plan on testing it with, you`re laughing )

[Radical Edward]

I suspect hanging something from the centre until it breaks.

[YT2095]

in that case you`re laughing! Torsion doesn`t apply, you can goto town on that one and make it almost indestructable