self-tapping screws in composite section

[cfloor]

Can anyone direct me to a website containing shear capacities of self-tapping screws for a shear load ±13kips (58KN) joining a 12Ga with 1/8 steel plate?

Second question: if I were to use these screws as a means for fastening rather than welding for full composite action shear connection resistance, Qr, does anyone think it's a poor design. It's just that screwing two light gage steel is quicker and more economical than welding... but, it strength is obviously shortcoming.

 

[UcfSE]

Check out Hilti or ITW Buildex. Hilti has better engineering information. You are looking for a #12 screw with a type 5 point. The type 5 point is extra hardened and the #12 diameter will not only give you more strength but can in some cases be better for drilling since it doesn't twist off as much when you're drilling to structural steel. I recommend Hilti personally, but use what is likely to be used in your area. Here in Florida Hilti, Tek and Grabber are popular. All should have information online for what you need. Make sure you are checking allowable loads. Many times manufacturers publish ultimates. Do not use the ultimate for design.

For the spacing of the screws you can check in section D of the 2001 AISI North American Cold-Formed Steel Specification. You can check for smax, screw or weld spacing, in that section. I typically use 12" o.c. and that almost always works. I don't often actually have to have the full composite action however. You must have some enormous loads, or torsion perhaps.

 

[Ron]

Have used similar before for composite section. Go to itwbuildex.com for sizes and shear values

 

[pba]

Are you planning on using the self drill screws to replace the headed shear studs to anchor the concrete slab to the steel beam to give you a composite beam section?

This sounds like a very bad idea. I work in the UK and under our codes this would not be allowed - there is a requirement for the studs to protrude above the deck profile so that they tie into the mesh reinforced concrete.

Hilti do produce a shot fired component to replace the welded studs. I don't have the info to hand but confirm that I've seen it on site and it seems to work well.

 

[cfloor]

I want to sincerely thank Ron & pba for their input... it meant a lot to me. With my new patented floor system using composite-action I thought of minimizing welding by replacing it with "easily drilled" screws. I found that even with Hilti, that the shear capacities for their best screw is NOT enough to be economical... I would need 12 screws to drill when only 5" fillet would suffice!

Nevertheless, what would you say to replace these screws with (2)-5/8"diam (A325) bolts to tie together two plates 12Ga-3/16"?

If you would like to see our floor system (composite joists) go to

http://www.cfloor.ca

 

[cfloor]

sorry I want to thank UcfSc too

 

[UcfSE]

You have to be careful about using high strength bolts with light-gauge materials. The bearing of the bolt on the steel section might control with larger diameters, especially with high strength material. It might be a waste to use A325 if the design strength is limited to a low value due to bearing.