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Steel beam supported with a wood column:

Steel beam supported with a wood column:

Steel beam supported with a wood column:

(OP)
Howdy all. I am working on a wood framed apartment building.  The floors are wood joist on wood load bearing walls. The corridor between units is metal deck and concrete. Large open areas in the corridor are desiged to be W-sections on HSS columns. As a VE item the architect wants to change the columns to wood (to negate the fireproofing cost). Size and span are factors in the beam selection. Steel is best for the deflection issues (L/360)and available depth (9" after allowing for mech ducts, concrete & deck). Is supporting steel beams on a wood column (probably a parallam or similar)accepted?  I'm using IBC 2003 and haven't seen a definiative "yes" or "no".  Any comments will be appreciated. Thanks.   

RE: Steel beam supported with a wood column:

(OP)
Forgot to add: siesmic cat. C and I did do a search and found information on masonry. thanks.  

RE: Steel beam supported with a wood column:

Connections would be a bit of a problem, especially if you need to develop moment connections, but I see no reason why you cannot support a steel beam on a wood column.   

BA

RE: Steel beam supported with a wood column:

I have done this too, but as mentioned above, no moment connection, simply bearing.  However, I do usually use pipe columns.

Mike McCann
MMC Engineering

RE: Steel beam supported with a wood column:

(OP)
I am assuming then that this is one of those "engineering judgement" issues.  

RE: Steel beam supported with a wood column:

(OP)
Ok, so then how do I apply this for multi-story buildings?

RE: Steel beam supported with a wood column:

You don't.

BA

RE: Steel beam supported with a wood column:

(OP)
Thanks.  

RE: Steel beam supported with a wood column:

I have often used wood columns in wood framed walls with steel I-beams because they shrink and expand as the walls do.  Steel/masonry won't move at all and this can be a source of drywall cracking.  The tallest was 3-story.

Remember to provide a contnous path for the columns to whatever is below.  We use "squash" blocks between sub-floors to transfer these vertical loads.

No complaints to date and have been doing so for many years.

Good luck.

RE: Steel beam supported with a wood column:

(OP)
Mike,
Awsome, thanks for the insight.   

RE: Steel beam supported with a wood column:

BC, Canada is a seismic area and they are entertaining using wood for 6 storey construction.

As far as steel beams on wood posts, I've used 3/16" side plates and glulam rivets for holding the steel beam to the post.

Dik

RE: Steel beam supported with a wood column:

Well, bully rodger and peachy keen!

BA

RE: Steel beam supported with a wood column:

BA... I don't like the height that they are/have considered and there is a lot of dialogue among the engineers in BC. Connections are generally the components that fail in a seismic event and the added height makes this more critical for wood.

Dik

RE: Steel beam supported with a wood column:

(OP)
Thanks guys.

RE: Steel beam supported with a wood column:

dik,

I won't say that you cannot use steel beams and wood columns in six storey buildings, but I'm pretty sure it wouldn't be my first choice.

BA

RE: Steel beam supported with a wood column:

(OP)
Yup, the way it was explained to me was "It's not a good idea, but the code doesn't say we can't do it."  Whatever, that means.  I haven't gotten the hang of "legalese" or as my fellow field friends would say "engin-jargon".  

RE: Steel beam supported with a wood column:

I have no problem with supporting steel on wood columns and have done it on a number of occasions. I can think of no reason why this would be a problem and one good reason why it may be a good idea (as stated above).h

Beware cross grain compression on wall plates e.t.c.

RE: Steel beam supported with a wood column:

Wood columns for steel beams is done all the time.  However, you are wood column capcity is exceeded fairly quickly with multi-story building with stacking point loads.  
The limiting factor is wood studs bearing on plates, a perpendicular to grain bearing area.
To help provide a good brace for the steel beam from rotation, be sure to provide studs the full width of the steel beam and a full height king stud each side.

MiketheEngineer hit on another good reason why to use wood studs when the rest of the structure is wood.  I've done many 4 story wood structures and always use wood columns when possible.  The lower levels tend to go to steel columns depending on the geometry of the structure.  Also, when the main structure is wood and your columns are steel, you loose any bracing from the sheathing nails.

Beware of a 4 story steel beam and column system that will not shrink while the rest of the structure will...   

Jim Houlette PE
Web: www.evstudio.us
Online Magazine: www.evstudio.info
 

RE: Steel beam supported with a wood column:

(OP)
Thanks for the information.  However, I have to make another post about the shrinkage issue.
 

RE: Steel beam supported with a wood column:

Longitudinal shrinkage of wood is minimal.

Dik

RE: Steel beam supported with a wood column:

Yes Dik
But the steel columns do not bear on plates right?
So you still have shrinkage across the grain at each plate, several stories it adds up.  

Jim Houlette PE
Web: www.evstudio.us
Online Magazine: www.evstudio.info
 

RE: Steel beam supported with a wood column:

It's a matter of detailing around this. Many old 8 and 10 storey warehouses had wood beams and columns.  They minimised movement by having cast beam seats bearing on columns.  I had understood he had steel beams and wood columns... little difference IMHO.  Dimensional stability would not likely be an issue. Floor to Floor movement should be accommodated by detailing.

Dik

RE: Steel beam supported with a wood column:

It's not just the plates, it's mainly the floor joists that contribute to shrinkage unless engineered joists such as TJIs are used.  If solid 2X10's are used, that's 9.25" of depth subject to shrinkage as opposed to 4.5" of depth for three plates per story.

So, 2/3 to the joists, 1/3 to the plates of the total shrinkage seen.

Mike McCann
MMC Engineering

RE: Steel beam supported with a wood column:

It's still a matter of detailing.  You accommodate the change in floor height from xxx to xxx +/-. Say the plates shrink 1/8" total and the joists shrink 1/2"... You have increased the floor to floor height by 3/8" (numbers pulled out of a hat). It's still a matter of detailing; the problem is there whether you have steel columns or wood columns... IMHO.

Dik

RE: Steel beam supported with a wood column:

I should add that it is common practice when framing wood joists into steel beams that the top of joist is typically 1" above the top of beam to prevent a 'hump' in the sheathing. Still a matter of detailing.

Dik

RE: Steel beam supported with a wood column:

Could someone clarify thanks? I'm not in North America.

All this discussion about shrinkage; is that because the non-engineered timber that you use is not kiln-dried?
I would only consider shrinkage if using green timber, and that would be very unusual where I am.

RE: Steel beam supported with a wood column:

The lumber used here should be kiln dried if spec'd, but unless you spec it, you may not get it.  

Even at a moisture content of 19% or less, kiln drying, you will still get shrinkage.  The effect should not be ignored, especially relative to finishes.

Mike McCann
MMC Engineering

RE: Steel beam supported with a wood column:

OK, thanks Mike.

RE: Steel beam supported with a wood column:

(OP)
I guess I should add some variables into this discussion:
-Due to cost we are using 2x material (southern yellow pine for joists, SPF for studs/columns).
-Any "engineered" lumber is kept to a minimum, again for cost (this is at the Archy's direction)
-We wanted steel beams/steel columns, but the Archy pushed the steel/wood combo, citing cost due to fireproofing.
-I only have 24" to work with, this includes conc. slab,mtl deck (5 1/2"combined), HVAC ducts (9" with insulation) and the support structure (?).
-Average beam spans are 13' with L/360 deflection limits (based on the deck/slab).
I'd like to thank everybody for your input. It is truely appreciated.  

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