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Replace wood with steel

Replace wood with steel

Replace wood with steel

(OP)
A friend of mine is trying to replace a support column and wood beam in his garage, which is under half of his house. He asked me, a structural engineering student, to suggest a steel beam that could replace the combined supports. The available space for the replacement is equal to the existing occupied space.
___________________________________________________________________________________________________________________
9.5”
___________________________________________________________________________________________________________________
-----------------------------11’--------------------I-----------------------------11’------------------------------
I
I
I 6.5’
I
I
I

Basically, what I tried to illustrate above, there are 3 2x10s together forming a 4.5” x 9.5” cross section that spans 22’ with a 6.5’ steel column supporting the middle. The column is a 2.5” diameter, 1/8” thick steel tube. There is no way to find the actual load that this assembly holds, but I want to find something that is reasonably effective and safe. My suggestion is 2 C7x14.5 beams, back to back of course. Can I get any recommendations from actual professionals?

RE: Replace wood with steel

Your "friend" should spend his own money rather than risk your reputation and future and hire a structural engineer. Since you do not have a stamp yet, he will need to engage a structural engineer anyway since he should get a permit for modifications of this magnitude.

Mike McCann, PE, SE (WA)


RE: Replace wood with steel

I agree with Mike. I'm betting you'll get no help of any value here...

RE: Replace wood with steel

I agree with Mike; assuming your friend lives in a jurisdiction that requires building permits he's going to need an engineer or architect to prepare the application. It seems that you're overlooking the need for temporary supports while the beam is removed; another reason to get an engineer.

Now don't take this the wrong way, BUT, if you're going to be a structural engineer how can you say "There is no way to find the actual load that this assembly holds"? As an exercise, there are two ways to do it: draw up the framing and calculate the loads or using the section properties of the members work backwards to determine their capacity. Use conservative values for shear and bending.

Why not use a wide flange? The channels need to be bolted together.

RE: Replace wood with steel

The owner intends to remove the steel column, right? If so, your proposed beam would have a span/depth ratio of 38. That's high and is going to trigger alarm bells in the minds of most structural engineers. And that's just one of a number of things to be looked at. Kick some concepts around with your friend but make sure that a licensed professional gets involved before it's all said and done.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Replace wood with steel

I'm just an electrical engineer, and I would be terrified of giving this kind of job to student who hasn't yet graduated. Most engineers here have probably forgotten more than you probably know, right now. This is not a trivial DIY project, and even experienced engineers can make mistakes; so, what kind of mistakes are you likely to be making in this?

TTFN
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Of course I can. I can do anything. I can do absolutely anything. I'm an expert!

RE: Replace wood with steel

(OP)
So, this type of beam replacement seems pretty simple, but you say it'll require a permit?

RE: Replace wood with steel

All works on a structure require permitting in most jurisdictions.

Sorry but you really are out of your depth. You need to tell your "friend" to contact a real Structural Engineer in your area who is qualified to undertake this engagement.

RE: Replace wood with steel

More apropos may be the Chicago deck collapse from 2003: http://en.wikipedia.org/wiki/2003_Chicago_balcony_...

The OP's problem may appear to be a "simple" one, but, the OP will learn that almost NOTHING is ever "simple." People LIE, drawings LIE, and construction LIES. Unless the OP is experienced enough to recognize where someone lied or omitted about what was done, the OP is potentially on the hook for unintentional deaths or injuries. Given that it's unlikely that the OP has the requisite professional liability insurance, their future in structural engineering could be very short indeed.

TTFN
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Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

Of course I can. I can do anything. I can do absolutely anything. I'm an expert!

RE: Replace wood with steel

(OP)
The column doesn't look like it's doing anything but providing backup. How about bolting half inch plate to the existing beam and remove just the column? Does that sound reasonable?

RE: Replace wood with steel

NO

RE: Replace wood with steel

You are neglecting the check of the new load path, the effect(s) on the remaining structure, you have no clue as to a reasonable deflection allowance to safeguard the SLS performance of the rest of the structure, etc, etc, etc.

Where are you studying? Just curious as I have found young Canadian graduates are shown so many disasters and collapses in their undergraduate degrees that many of them are frightened of their own shadows, needing hand holding for years in some cases. The New Zealand graduates are far less fearful, but know enough to know what they don't know, and to refuse work outside of their depth. You seem rather confident to continue guessing, to the detriment of your future career.

Man (or woman) up and tell your friend to go hire someone local. Worst case you're going to get yourself or someone else HURT; best case is significant economic loss or collapse of this structure.

RE: Replace wood with steel

(OP)
Thank you all very much for the advice. I'm glad to see that professionals care so much about safety. I think I'm going into the right career.

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