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beam continuous bracing by grating attachment
2

beam continuous bracing by grating attachment

beam continuous bracing by grating attachment

(OP)
At what interval would clips be required for grating attachment to provide adequate continuous bracing of the compression flange of the support beam?

RE: beam continuous bracing by grating attachment

I do not recommend using grating attachment for bracing the compression flange of beams. Instead, we brace them with angles at right angles to the beams and provide diagonal angles back to the beam support.

RE: beam continuous bracing by grating attachment

I agree with jike, The grating attchments are not desined for the type of loads required to brace a beam.

csd

RE: beam continuous bracing by grating attachment

We don't rely on the grating for bracing.  We provide beams at right angles to the grating support.

RE: beam continuous bracing by grating attachment

(OP)
Thanks to those who responded.  I should have also mentioned that this is an existing platform and obstructions, (piping), prevent adding steel for bracing.  We are trying to maximize allowable live load by using existing grating, (currently not attached), to restrain support beams against lateral displacement.  I know the situation is not optimal, but we want to make the most of the cards we've been dealt.  Thanks again for your contributions.  I hope to hear some more...

RE: beam continuous bracing by grating attachment

I do not rely on grating for beam bracing.  Can the grating be removed in some areas to allow bracing to be installed from above?  Or do the obstructions prevent bracing to be installed from above?

RE: beam continuous bracing by grating attachment

(OP)
Installing bracing is not an option.  We want to utilize the inherent strength of the existing 1" thick grating.  Thanks.

RE: beam continuous bracing by grating attachment

Pete2006,

What is your span length? What is the size of the main beams?

RE: beam continuous bracing by grating attachment

(OP)
Beam span is 18 feet and it's a W12x16.

RE: beam continuous bracing by grating attachment

Pete2006,

How close are you from making the beams work if you consider the compression flage unsupported?

RE: beam continuous bracing by grating attachment

(OP)
Unbraced beam governs max live load at about 40 p.s.f.  Grating deflection would otherwise govern at about 140 p.s.f.  Adequately braced beam would potentially exceed grating capacity.

RE: beam continuous bracing by grating attachment

I'm with jike, csd72, jmiec, and archeng59: I don't count on grating for beam bracing.

RE: beam continuous bracing by grating attachment

Only thing I can suggest would be to cap the W12 with a channel (say, C10x15.3), and design it like a trolley beam.  Combined properties and shown in the 9th Edition.

RE: beam continuous bracing by grating attachment

I probably would take an exception to all the comments above.
I personally think that if the metal grating is rigid enough, welded continuously to the main beam compression flange and the main beam spacing is not so large, then I would conside the main beams to be braced. Lateral bracing will only require to handle 2% of the total compression force in the member.

RE: beam continuous bracing by grating attachment

I would tend to agree with shin25, and consider the the beam braced with (2) requirements:  (1) Steel deck grating (not alumninum, extruded plastic, etc.) and (2) the grating is welded to the beam flange.  If the only attachment is by the deck clips, then I would not consider the flanged braced.

RE: beam continuous bracing by grating attachment

In lieu of all this arm waving and opinions, why don't you just quantitatively check the grating?  Boom, done, question answered, no guessing, no waiting for what you want to hear.

RE: beam continuous bracing by grating attachment

(OP)
UcfSE,
Thanks for your post, though I don't know how a quantitative check of the grating would help me determine the allowable bending stress of the beam, which is currently the limiting factor as it is not braced against lateral displacement. (I know the meaning of the word "quantitative", but don't know what you mean in your application.  You mean load it to failure?  If so, not practical).  I'm sure your approach has merit - please clarify.

RE: beam continuous bracing by grating attachment

I mean check with engineering whether the grating is adequate to brace the beam.  So far we've answered only with opinions.  I think you should either disregard the grating, as many have suggested, or actually check it for adequate strength and stiffness to brace the beam.  The AISC provides some guidance as to the strength and stiffness requirements for bracing.  Note you have to meet both.  If you can't get the information you need to check it, then there's your answer: don't use it.  

You may also try looking into research papers to see if anyone has tested this arrangement for its performance as a system.  What I'm getting at is I don't think it's adequate to say it's ok without checking anything with numbers, especially with so many opinions to the contrary.

RE: beam continuous bracing by grating attachment

UcfSE,

If the grating has a load capacity of 140 psf on a given span without much deflection, I think that should give some clue about its rigidity, should it not?

RE: beam continuous bracing by grating attachment

Three clips per end of grating panel, (35 13/16" width), is sufficient to anchor grating to the top flange of a steel beam/channel for bracing purposes.  Also banded ends with welds to the top flange will also work.  If the grate is removed, the load is usually also missing so grate is a suitable continuous brace. Referencing 1 1/4" deep, 3/16" bars, steel either welded or swaged into units.

RE: beam continuous bracing by grating attachment

Sooner or later, the grating will be removed to access the equipment below.  In many, perhaps most, cases when
grating is removed, the clips are not replaced.  The grating is simply laid on top of the beams.  Bye-bye lateral support.

I can see grating welded to the top flange as providing bracing to the beam, provided that the grating is similarly attached to something rigid enough to provide lateral support, like a foundation wall.  Two parallel beams cannot provide bracing to each other in this manner.

RE: beam continuous bracing by grating attachment

There are many different kind of clips that are used and I would not claim that any clip will provide adequate support. They maybe OK for uplift but not for lateral!

RE: beam continuous bracing by grating attachment

Three clips per panel end,(35 13/16" wide), is sufficient to use 1 1/4" deep steel grating, (3/16" thick bars), as top flange brace.

RE: beam continuous bracing by grating attachment

shin, clue yes.  But how much?  It doesn't help with that.  As the EOR, it's our prerogative to decide whether to assume a condition or to check it, and then proceed accordingly.  My advice is not to assume grating works.  That's just my opinion. smile

RE: beam continuous bracing by grating attachment

I would go with MarchSE's answer.  (Also check the other end of the grating to make sure it's welded to something there- if not, a weld at the beam doesn't help much.)  On the rigidity question, you'd also need to look at the other end as well.

RE: beam continuous bracing by grating attachment



Quote (civilperson):

Three clips per panel end,(35 13/16" wide), is sufficient to use 1 1/4" deep steel grating, (3/16" thick bars), as top flange brace.

Is there something in the literature, such as a research report, to back that up?

RE: beam continuous bracing by grating attachment

Three connecting clips per panel end, (panel width of 35 13/16"), is sufficient for 1 1/4" deep 3/16" wide steel bars on 1 3/16" spacing with welded or swaged cross members.  This amount of connection strength works for bracing top flange of most beams less than 18" in depth.  There is over seven square inches of steel area in a panel cross section as described above so the amount of bracing available is significant.

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