Angle Iron Strength


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Old 01-25-13, 05:52 AM
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Angle Iron Strength

I have a piece of angle iron 6" on one side and 4" on the other that I want to use for 4 beams to sit on. My question is this. With the 6" side going vertically and the 4" side going horizontally, which way is the angle iron strongest, with the 6" side up or with the 6" side down?
All comments appreciated.
 
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Old 01-25-13, 05:58 AM
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6" side up. But you might be using the wrong sort of iron for this application... you might need to look into a steel I-beam. Specific information regarding what you are doing would probably help.
 
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Old 01-25-13, 06:40 AM
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Just in case I am not describing it correctly, attached is a photo of the 2 examples.
 
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Old 01-25-13, 06:45 AM
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If placing a load on top of the beam that will be bearing down I would have the 6" web vertical and the 4" web horizontal. It all depends on how the load will be applied to the beam though.
 
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Old 01-25-13, 08:36 AM
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I am not saying to have the 6" side horizontally, it is common sense that the 6" side is stronger and should only be installed vertically. My question is if the 4" side be on top or on the bottom of the vertical 6"?
It probably doesn't make a difference but I've updated the image, maybe that makes my question more clear.
 
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Old 01-25-13, 10:11 AM
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I would keep the 4" leg down so the beams sit in inside the L so that if the fasteners did loosen for some reason, the ends of the beams keep it from tipping and prying the bolts out of the wall.
 
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Old 01-25-13, 11:32 AM
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When you start talking beams and steel angle like that it makes me think engineered. Do you need an engineer's approval for the work? They will be able to tell you how it needs to be done. So far you've only told us a bit but you've not mentioned the span or the load the beams will place on the beam that will affect how to properly orient it. If placed on it's side it may not properly support the load.
 
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Old 01-25-13, 01:01 PM
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That what I had envisioned but then I started thinking about what would be strongest.
 
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Old 01-25-13, 01:17 PM
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I'll admit, I didn't do to well in my mechanical engineering classes... but I'll throw my thoughts in the ring anyway...

If you can get whatever beams are held up by this to extend across the whole flange, I would choose option B. The strongest point on the angle iron is directly above the vertical section. The more you go outward toward the edge of the 4" section, the angle iron will try to torque. So option A, you have at least the 1/2" or so offset the strongest point.
This is why I or C beams are used more often for structural support, the shape prevents torquing/twisting.

How much it really matters though, I'm not sure...
 
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Old 01-25-13, 02:38 PM
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Thank you very much Mike for helping me understand why it would be best to use the angle iron pictured B.

Now here is another question. How can I modify/strengthen the angle iron pictured A to compensate for any torquing/twisting? This will be installed in the basement with short ceilings and I would rather not have anything protruding from the ceiling.

Ultimately, I would prefer to install the angle iron as pictured in A, will modifying the angle iron as pictured below strengthen it and make it it more difficult to torque/twist?
Name:  angleironreinforced.jpg
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Old 01-25-13, 04:25 PM
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A lot od opinions without knowing what length the angle will span.

An angle in non-symmetrical and the twisting for a longer distance will cause a much quicker failure than with a symetrical cross-section. - That is why beams for longer sections are always symmetrical. Welded connections can help somewhat because they help provide a more positive connection.

Any time you rely on a odd cross-section the load capacity is less.

If it for decoration, strength is not a problem.

Dick
 
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Old 01-25-13, 08:03 PM
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I just went down to the basement and took another look, I think I might need something heavier. The angle iron is to span 10'. There are 8 3x8x15' long floor joists that will sit on it. The only thing the joists carry is the wood floor, that's all.
 
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Old 01-25-13, 08:20 PM
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At the risk of repeating myself, I think you need a steel I-beam... and an engineer. Oh, where is Bridgeman45 when you need him?
 
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Old 01-26-13, 07:03 AM
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I have to agree with XSleeper, I think an I-beam is what you need. You're not going to get the stability from a piece of angle iron.

As far as I know, if sized appropriately, you can insert the wood beams into the I-beam, sitting on the bottom flange, so you don't lose headroom. The I-beam needs to be sized correctly for this, and I'm not the person to help with that.
 
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Old 01-26-13, 07:48 AM
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Although an I beam would probably be best and most efficient, it is not practical at this point.

This is for a stairway opening. What I am looking to do is replace an 8x8 wood beam that the joists are sitting on. There were no headers built and the 8x8 wood log is coming down from an already short ceiling. It would be easier for me to either a.install a heavier angle iron(maybe a 7" or 8") or b. lessen the span by maybe installing a post or a concrete column somewher in the middle of the 10' stretch, or possibly both options a. and b.
 
 

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