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Old 07-24-2008, 07:55 AM   #1
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How to Reinforce Steal I-Beam


I am creating a theatre room in my basement, but have an unsightly support post in a bad position in the room. I've consulted a structural engineer who has indicated I can take that support post out if I reinforce the existing metal I-beam with 1/2" rebar welded to the upper inside corners of the I-beam. Have you ever heard of this?

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Old 07-24-2008, 08:35 AM   #2
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How to Reinforce Steal I-Beam


I'd strongly question that engineer's advice. Welding of mild steel rebar in a structural application is just not done, and it is a poor idea. Yes, it can be welded, but how effectively?

This is from Wikipedia:
Most grades of steel used in rebar cannot accept welding; such as, to adjacent steel plates or as means to bind single pieces of rebar together. However, special grades of rebar steel and welding rods make welding by expert welders possible.

Any good engineer would have specified steel flat (rectangular) stock, which is the same material as your beam, and the shape lends itself to welding to flat surfaces.

Also, adding material to the upper edges of the beam doesn't make sense to me. The removal of the post would make the tension forces in the bottom of the beam even greater, and they occur in the bottom flange of the beam. Not to say that the top won't need beefing up as well.

I don't know what your spans and loads are, but that post is there for a reason. I think you need to consult another engineer for a second opinon, and also have them inspect the welds for proper penetration.

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Old 07-24-2008, 09:24 AM   #3
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How to Reinforce Steal I-Beam


"thekctermite" makes a very good point. I can't imagine welding anything inside a house!

Can you sister the beam with Paralam or Microlam?

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Old 07-24-2008, 11:16 AM   #4
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How to Reinforce Steal I-Beam


Welding indoors doesn't concern me too much, as it is done fairly regularly on projects such as this. What's being welded...That's another story.
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Old 07-24-2008, 11:44 AM   #5
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How to Reinforce Steal I-Beam


I'm wondering if channel iron could be sistered on both sides of the beam. These would be bolted in place by drilling through the channels and the beam web.
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Old 07-24-2008, 01:25 PM   #6
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I'm wondering if channel iron could be sistered on both sides of the beam. These would be bolted in place by drilling through the channels and the beam web.
Certainly could, although most engineers will specify welded connections. Otherwise the shear strength of the bolts comes into play, and there would need to be a lot of them. The web of a steel beam is not nearly as important as the flanges. I suspect that beefing up the flanges is in order. I normall see them specify a certain thickness of rectangular bar welded to the underside of the bottom flange.
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Old 07-24-2008, 06:35 PM   #7
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How to Reinforce Steal I-Beam


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Originally Posted by sranders0n View Post
I am creating a theatre room in my basement, but have an unsightly support post in a bad position in the room. I've consulted a structural engineer who has indicated I can take that support post out if I reinforce the existing metal I-beam with 1/2" rebar welded to the upper inside corners of the I-beam. Have you ever heard of this?
This guy sounds like a train engineer. The solution is stupid.
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Old 07-24-2008, 08:04 PM   #8
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get another opinion form a strucural engineer..i have welded round stock per stamped drawings in the upper flanges of bar-joists to beef up the roof for additional snow loads and i have also been instructed to weld angle iron to "box" in the upper and lower flanges of beam in the roof of an arena for snow loads as well, due to another structure added to the side of the building that is higher than the roof i welded on

and in a case like you describe i have been directed by a structural engineer to add flat bar that touches both top and bottom flange , 1 inch in from the outer edge of the flange on both sides and welded 1/4" fillet 2 inches long every 6 inches

i guess every application has it's own needs or is it the preference of the engineer, but i think using rebar is silly as most rebar (unless specifically stamped) is not much good for anything strucural
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Old 07-24-2008, 08:55 PM   #9
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As a follow up; I've explained the solution to two additional engineers, and neither have heard of this solution. I also went back to the original engineer and question whether it's been done in the trade, and again the answer was 'frequently'. The reason I want to believe in the idea is because it is the least evasive, i.e. I don't lose headroom by adding metal to the bottom of the i-beam, and I don't have to install a completely new, heavier, beam. So, am I correct when I say most of you don't like the rebar idea, but if it were a solid square metal rod it would make more sense?
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Old 07-24-2008, 10:48 PM   #10
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How to Reinforce Steal I-Beam


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Originally Posted by sranders0n View Post
I am creating a theatre room in my basement, but have an unsightly support post in a bad position in the room. I've consulted a structural engineer who has indicated I can take that support post out if I reinforce the existing metal I-beam with 1/2" rebar welded to the upper inside corners of the I-beam. Have you ever heard of this?

Sranders0n:
I graduated from mechanical engineering in 1978, and though I have never worked as a structural engineer, I still remember and understand the principles involved.

Now, this fellow told you that you could remove the post if you welded rebar to the "upper inside corners" of the I beam. Does he mean weld the rebar to the inside corner where the central web meets the upper flange on both sides of the web? If so, then I can assure you that this person knows not of what he speaks. I can assure you that even if you were to weld 1/2 inch rebar to both the upper and lower corners where the web meets the flanges, you probably wouldn't strengthen the beam enough to remove that support.

You see, the span of a beam is one of the most important parameters in determining the deflection of a beam. If you double the span, then the deflection increases by 2 raised to the 4th power, or 16 times what it previously was. If you triple the span of a beam, the deflection increases by 3 raised to the 4th power or 81 times what it previously was. So, if you want to remove a support column, and the result will be a doubling of the span between the remaining supports, then you're going to have to probably replace that beam with a much larger beam rather than modify it. Alternatively, you might be able to weld another I beam to the bottom of the existing I beam to provide the additional support. That is, support your existing I beam while you remove the column, position a second I beam below the one you have, and weld the two I beams together.

I'd say your best bet would be to take the problem to any structural engineering firm and ask them what they envison as a practical solution.

I think there's a good bet that they'll tell you that you need to replace that I beam with a larger one because you simply can't modify it in a cost effective manner to increase it's strength to the amount needed.
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Old 07-24-2008, 10:53 PM   #11
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So, am I correct when I say most of you don't like the rebar idea, but if it were a solid square metal rod it would make more sense?
Sure would, even though it is still a lousy fix. The shape of the rod isn't the issue. You could use round stock, although it might be trickier to weld. The issue is the mild steel that rebar is made of.

Your engineer may do it all the time, but that doesn't make it right. As a building inspector, I will allow an engineer to design structural repairs 99.9% of the time, and will honor their call because they have the engineer's stamp . But I assure you that there is no way that I would accept such a misguided repair as to weld rebar to a steel beam.

I'll caution you that not all engineers are good at what they do. Until he recently retired, we had an engineer in this area that would sign off just about anything for $300. It became a service for crumby builders to circumvent minimum structural code requirements. I've rejected his work on a number of occasions and for good reason, and I've begrudgingly accepted more than I wish I had. He's been in court defending himself countless times, and somehow still ended up keeping his business profitable.
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Old 07-25-2008, 09:48 PM   #12
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Originally Posted by sranders0n View Post
As a follow up; I've explained the solution to two additional engineers, and neither have heard of this solution. I also went back to the original engineer and question whether it's been done in the trade, and again the answer was 'frequently'. The reason I want to believe in the idea is because it is the least evasive, i.e. I don't lose headroom by adding metal to the bottom of the i-beam, and I don't have to install a completely new, heavier, beam. So, am I correct when I say most of you don't like the rebar idea, but if it were a solid square metal rod it would make more sense?
I have never seen anything close to this done, and it would not be a DIY project anyway. Two engineers say no, one tells you what you want to hear.....without knowing the loads imposed on the beam, the advice given here is not worthwhile, but for thought, I would listen to the other engineers....plating the beam, both sides, with something like a cold form 3/8 plate as wide as the web would allow may be a solution for you. Drill and bolt with 1/2 inch grade five bolts about every 3 feet. No welding, due to the possibility of destroying the tensile strength of the beam.
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Old 07-25-2008, 10:49 PM   #13
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I have never seen anything close to this done, and it would not be a DIY project anyway. Two engineers say no, one tells you what you want to hear.....without knowing the loads imposed on the beam, the advice given here is not worthwhile, but for thought, I would listen to the other engineers....plating the beam, both sides, with something like a cold form 3/8 plate as wide as the web would allow may be a solution for you. Drill and bolt with 1/2 inch grade five bolts about every 3 feet. No welding, due to the possibility of destroying the tensile strength of the beam.
It was my thought that channel iron, sistered on both sides, with bolts to the beam web (earlier post) would be a better idea than welding re-bar.
I think the channel iron would have better structural integrity than a steel plate, also!

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