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Old 07-05-2011, 05:47 PM   #1
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deflection in 8" Steel I Beam?


I am in the process of gutting the basement for a renovation and I just noticed what looks like a deflection in the steel I beam that runs 2/3rds the length of the house.. it's a 40' I beam that is 8x8 inches the far end its resting on the concrete block wall the other end it butts together with a perpendicular I beam that runs 40' also where they butt togheter they are welded into each other and under the seam they are supported by a steel column. the beam I am talking about only has one other support along its length which is about 17' from the concrete block wall, so its supported at 0 ft, 17' and 40 ft so there is about a 20' section that is not supported from below.

This is the portion that has a deflection to it... should a span that long that is supporting a 1 1/2 story house have more supports under it?

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Old 07-05-2011, 06:04 PM   #2
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deflection in 8" Steel I Beam?


It is impossible to second guess thw installation of this beam with the information you have posted

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Old 07-05-2011, 06:44 PM   #3
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deflection in 8" Steel I Beam?


If you are in the process of gutting the basement for a renovation, is this a DIY or are you a contractor? If you are a contractor (i.e. you are getting paid to do this job), this is the wrong forum. If you are DIY, you need to hire an engineer to evaluate your question, no one can reasonably answer your question without personally visiting the site.
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Old 07-05-2011, 07:55 PM   #4
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deflection in 8" Steel I Beam?


Do you have a deflection criteria that you are trying to meet? I would assume that your total load deflection should be no more than an inch. You would probably have to put about 1000 plf of load on that beam to get it to deflect that much. Do yo have any idea how much load that beam is seeing?
Are you having a serviceability problem with the current deflection? Is that why you are asking?

I'm going to have to agree with Daniel that you should hire a structural engineer to come out and look at it. But that may cost you a couple hundred bucks to have someone come out, run a 2 minute calculation, and say, "yeah, this is fine."
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Old 07-05-2011, 09:31 PM   #5
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deflection in 8" Steel I Beam?


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If you are in the process of gutting the basement for a renovation, is this a DIY or are you a contractor? If you are a contractor (i.e. you are getting paid to do this job), this is the wrong forum. If you are DIY, you need to hire an engineer to evaluate your question, no one can reasonably answer your question without personally visiting the site.

no I am just the home owner, the only reason I am wondering about this is because I noticed what looked like a bow in the beam in comparision to the HVAC trunk line that runs right infront of it... therefor I am curious if this is a problem or not
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Old 07-05-2011, 09:34 PM   #6
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deflection in 8" Steel I Beam?


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Do you have a deflection criteria that you are trying to meet? I would assume that your total load deflection should be no more than an inch. You would probably have to put about 1000 plf of load on that beam to get it to deflect that much. Do yo have any idea how much load that beam is seeing?
Are you having a serviceability problem with the current deflection? Is that why you are asking?

I'm going to have to agree with Daniel that you should hire a structural engineer to come out and look at it. But that may cost you a couple hundred bucks to have someone come out, run a 2 minute calculation, and say, "yeah, this is fine."
well the bow isn't huge, maybe 1/2" to 3/4" max I haven't ran a level laser line down the length yet to measure it like I said above, I am just curious if these do bow like this or if its a problem that I do need an engineer for... the house plans that are certified by an engineer had exactly how it was built by what I can tell, so I'd assume they did calculations when they designed the structural and framing plans..

just curious and a slight be concerned when you notice something looking bowed a little

all this renovation has got me ultra sensative to plum and level just by looking at it at this point...
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Old 07-05-2011, 10:10 PM   #7
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deflection in 8" Steel I Beam?


Well in my neck of the woods that beam should have at least one more column under it for support but as suggested there is really no way to give you the right answer. The only person who can do that is a structural engineer who visited the site and did his calculations based on his findings.
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Old 07-05-2011, 10:33 PM   #8
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deflection in 8" Steel I Beam?


If your drawings have been signed and sealed by a structural engineer, I would assume the beam is fine.
As long as you are not changing the framing of the house (ie, you are not changing the load distribution on the beam) and you are not adding much more live load to the beam, the beam should be fine.

3/4" deflection in a 23' span sounds fine to me. You typically want to stay under L/240 for a total load deflection criteria (so, 23 feet x 12 in/ft divided by 240 = 1.15" maximum allowed deflection.)

This beam isn't being used to support a grand piano or a 4000# safe, right?

8" deep beam for a 23 foot span sounds light, but I suppose this is fine since it is in a house and not a commercial building. You don't see many steel beams in home construction.

As always, when in doubt hire an engineer to come out and look at it.
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Old 07-05-2011, 10:40 PM   #9
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8" deep beam for a 23 foot span sounds light, but I suppose this is fine since it is in a house and not a commercial building
We also don't know the size of the beam. Big difference between a S8X9.25 and a W8X94 !

Beams also get "pre deflected" as it were, between the mill, the boat, the trucks, the crane and four knuckle-heads on forklifts
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Old 07-05-2011, 10:41 PM   #10
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deflection in 8" Steel I Beam?


Seems odd to have that much space between supports poles unless someone removed one. Is there any evidence on the beam or the floor where there might have been a pole?
If it bothers you, jack up the beam and add another pole(and footing).
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Old 07-05-2011, 10:55 PM   #11
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We also don't know the size of the beam. Big difference between a S8X9.25 and a W8X94 !

Beams also get "pre deflected" as it were, between the mill, the boat, the trucks, the crane and four knuckle-heads on forklifts
He mentioned that it was an 8"x 8" beam, so I figured it was a W8x31 at least...
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Old 07-05-2011, 11:01 PM   #12
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deflection in 8" Steel I Beam?


I was just joking, I actually missed the 8X8 part. I don't have a book with me, so I couldn't even guess anything other than it must be a W or a miss used H
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Old 07-05-2011, 11:30 PM   #13
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deflection in 8" Steel I Beam?


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Seems odd to have that much space between supports poles unless someone removed one. Is there any evidence on the beam or the floor where there might have been a pole?
If it bothers you, jack up the beam and add another pole(and footing).

nope, nothing missing.. no weld marks or anything else that would of given it away another pole was around the pans only call for two poles one at the joint and one around the middle of the beam span
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Old 07-05-2011, 11:32 PM   #14
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deflection in 8" Steel I Beam?


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8" deep beam for a 23 foot span sounds light, but I suppose this is fine since it is in a house and not a commercial building. You don't see many steel beams in home construction.

As always, when in doubt hire an engineer to come out and look at it.

yeah, not sure why they went steel I beam, but they did! all the other houses around here have 2x12's sistered up (3 or 4 of them) to form a main beam it seems like, this is one of the few houses that has a steel I beam in the negiborhood
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Old 07-06-2011, 07:01 AM   #15
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deflection in 8" Steel I Beam?


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yeah, not sure why they went steel I beam, but they did! all the other houses around here have 2x12's sistered up (3 or 4 of them) to form a main beam it seems like, this is one of the few houses that has a steel I beam in the negiborhood
They probably had a pool table. A lot of posters want to remove poles so they can play pool.

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