Welded studs to transfer lateral load 2

[3doorsdwn]

I have a situation where I have a concrete diaphragm/slab sitting on a steel beam, and I want to transfer some horizontal force into this beam using welded [shear] studs. The beam is sized to where it will be just fine without any composite action, BUT the number of studs I'm coming out with (for the transfer) are very small. So I am just wondering should I use some sort of minimum number of studs so that the studs are not damaged from some sort of [attempted, partial] composite action? One reference I read said to use (as a minimum) 25% of the number of required studs for full composite action. But I can find nothing in the code (officially) for this. Thoughts?

 

[ishvaaag]

This is some quite interesting problem the solution of which I think resides in study at the limit state. If one comes to the simplifying thought of that for a steel beam competent without any need of composite action to support the vertical loads the slab is thought to rest on the bean (accompany it in its downwards deformation) one would be able to dismiss any thought of tensile action on the stud (as an applied load at the interface) and the problem becomes simplified to add two shears, the one coming from the tributary shear at the interface for the stud in the actual composite action allowed by the competent beam without need of such, and your purposedly transmitted shear; vectorial sum of both to be competently taken by the studs at the given separation. So I think you can calculate the thing well this way.

 

[slickdeals]

Is your end connection designed to carry shear and axial forces?
You may also want to read this article

http://www.modernsteel.com/Uploads/Issues/December_2008/122008_steelwise_pdf.pdf

 

[WillisV]

I would use a 25% minimum (as slickdeals reference suggests) to avoid damaging the studs due to the composite action that will result from gravity loads (the beam doesn't know you don't want it to act compositely under gravity load). You will not find this limit explicitly in the codes, but p16.1-311 (the Commentary to I3) of AISC 2005, item 3, recommends this limit.

 

[JAE]

You might do a search here on Eng-Tips - there was a thread on this topic at one time that discussed all the issues involved - especially the concern that the flexural composite action on the studs and the lateral drag had to be combined properly - the studs on one half of the span getting higher stress than the other half due to the direction of the lateral drag of teh diaphragm into the beam.

 

[msquared48]

I generally set the minimum number of studs at 12" on center for the full length of the beam and see where that puts me. Usually, it's more than enough, but simple for the contractor to place.

Mike McCann
MMC Engineering

 

[BAretired]

I vote for Mike's solution.

BA

 

[3doorsdwn]

Thanks for the feedback everyone.

 

[ishvaaag]

More or less what I was saying in a printout...

 

[ishvaaag]

The check of the stud may be a bit more complicated than just by the formula considered. As in the comics, Methinks 6" is too little depth for a 3/4" connector. Go for the code.