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Deflection limit for steel beams supporting masonry partitions

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ajk1

ajk1

Structural
Apr 22, 2011
1,791

It has been suggested that steel beams of floors supporting masonry partitions be designed for a service load vertical deflection limit of span divided by 500 or 600 or perhaps even more stringent, to minimize the possibility of the partition cracking due to beam deflection. This would be under specified live load plus load applied after the partition is built, as well as the self weight of the partition.

Where is that limit given? Is it in the National Building Code of Canada or its User's Guide, or CSA S16.1? I can't find it, but I don't have the latest versions here at home. Or if not there, then where? Perhaps in NRC notes or an American publication?
 
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See commentary D of the structural commentaries in the NBCC. Table D-1 note 2. vertical deflection of masonry wall supports must be less than l/480 or 20mm.
 
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Across your southern boarder, it's l/600 or .3"
 
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Thanks jayrod.
To hawkaz - can you tell me which American Standard gives the L/600 or 0.3" (8± mm)?
Thanks.
 
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If Hokie66 is on here, can you tell me what the Australian Standard says in this regard?
 
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AS1170.0 Table C1 - mid span deflections for floors supporting masonry walls is limited to L/500. Mid span deflection for underpinning beams supporting existing masonry walls is limited to L/750.
 
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Thanks nineninenine. Much appreciated.
 
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This is from the Australian code AS4100

Capture_qgsiqm.jpg
 
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Thank you Retrograde. A good Table to have. Does the Australian Code or Commentary explain or give examples of what they mean by "where provision is made to minimize the effects of movement"? It seems rather vague. Would a deflection space between the top of the wall and the underside of the floor structure above be considered as provision to minimize the effect of movement? Would provision of horizontal joint reinforcement be so considered? Or do they mean the provision of vertical control joints in the masonry?

Also, is the self weight of the wall to be included in the calculation? It would seem from the wording "after the addition of the partition" that the self weight of the would not be included, but I think self weight generally would be included...this wording is, in my opinion, a problem with Canadian and American Codes/Standards as well(although I have not looked at all of them).
 
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I was looking at ACI 530-05, section 1.10.1.
I pulled up ACI 530-11, it is now section 1.13.1.4.1, but I don't see the .3" limitation anymore (l/600 still applies)
 
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Thanks Hawkaz. Does it say whether the weight of the wall is to be included in the deflection calculation?
 
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It doesn't specifically mention this, but with the wall weight being DL, I have always included it.
 
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ok, thanks very much hawkaz.
 
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ajk1 said:
Does it say whether the weight of the wall is to be included in the deflection calculation?
Click to expand...

I've always included it in new builds. However, in an unshored application where a non-bearing wall above will be constructed quickly in one go, I think that you could make an argument for excluding the weight of the block. I think that you're only really interested in curvature that develops after the mortar sets.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
 
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I have always used l/600 minimum, and sometimes l/1000 depending on the situation.

Mike McCann, PE, SE (WA)


 
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Ajk1:
Whatever the final stl. beam deflection, you might consider making the bottom couple courses of the conc. blk. wall a horiz. reinforced masonry beam. Make the bot. course out a bond beam blk. with some rebar. Fill the next course of regular blk. with grout also, and put some joint reinforcing in several of the lower joints. This will help the whole wall act as a deep beam, and do some of its own spanning was the stl. bm. starts to deflect. It will also inhibit any cracking from the bottom of the blk. wall due to the stl. bm. deflection. It will relieve the blk. wall loading on the center portion of the stl. bm., as the stl. bm. starts to deflect.
 
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ok.

And thanks dhengr for the good idea. Much appreciated.
 
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ajk1 said:
Thank you Retrograde. A good Table to have. Does the Australian Code or Commentary explain or give examples of what they mean by "where provision is made to minimize the effects of movement"? It seems rather vague. Would a deflection space between the top of the wall and the underside of the floor structure above be considered as provision to minimize the effect of movement? Would provision of horizontal joint reinforcement be so considered? Or do they mean the provision of vertical control joints in the masonry?

Also, is the self weight of the wall to be included in the calculation? It would seem from the wording "after the addition of the partition" that the self weight of the would not be included, but I think self weight generally would be included...this wording is, in my opinion, a problem with Canadian and American Codes/Standards as well(although I have not looked at all of them).
Click to expand...

The Code does not elaborate but generally I would consider both provision of horizontal joint reinforcement and the provision of vertical control joints are acceptable.

Normally I would include the weight of the partition in the calculation.
 
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Thanks very much Retrograde for your wise counsel and help. It is very useful and much appreciated.
 
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