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.
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...
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?
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.
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.
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.
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.
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.
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.
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.
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?
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.
