Diaphragm - Shear Studs

[DYork]

I have a two story steel construction. The 2nd floor is designed with deck w/ 6" layer of concrete. The floor was not designed as composite members, however I need to develope the floor for diaphragm action. Is there a good reference for shear stud design for this type of design? Thanks.

DYork

 

[J1D]

Stud spacing = diaphram shear(lb/ft)/stud shear capcity.
BTW, with studs and 6" concrete, why not to consider composite, at least for shear?

 

[JAE]

DYork - what do you mean by "diaphragm action"? Are you saying you want to use the floor slab as a large diaphragm to transfer lateral loads to braces? Or are you simply saying you want to engage the slab; tie it into the beams, to develop composite action and thus increase your floor capacity to take larger gravity loads?

 

[DYork]

JAE: - I need the floor to transfer the load to braces, do not need it the coneection for composite action to increase gravity loads.

DYork

 

[haynewp]

I think the studs will be acting compositely with the beam even if you don't want them to. I would calculate the force to the studs due to whatever gravity loads you are combining with lateral, then add the lateral force to the studs from the diaphragm. Sorry, I don't know of a reference for you.

I have seen buildings that did not have composite beams (as in your case), but they did not put in studs to transfer the slab diaphragm force to the lateral system. It is kind of concerning. There is some bond between the slab and deck then the deck is welded to the beams, and then there is bearing of the slab on the face of the columns that are in line with the brace(if columns penetrate the slab) that would help get the lateral forces into the floor beams. But I doubt these methods were really thought about.

 

[JAE]

haynewp - good description of the load path - I note that Vulcraft and SDI do have deck tables (with concrete) that give diaphragm shear strengths but never add any description of extra studs.

I believe that the deck tables deal with the connection to supports and this will take care of the deck shear to the supporting collector beams (through the weld or screw from deck to beam.

 

[imnotclever]

JAE,

My question about the Vulcraft and SDI deck tables: How do these relate to composite design. These tables must only relate to non-composite design, right? I mean as soon as I weld that stud through the deck I should have the ability to transfer as much shear as the stud will take and the deck tables shouldn't apply any longer. Right?

 

[Taro]

JAE,
Check out Verco's deck catalog. Table 5 on page 20 gives increased allowable diaphragm values for decks with shear studs.

 

[JAE]

Taro,
I don't have their catalog - does the new SDI Diaphragm manual have this? We have the Second Edition and it doesn't seem to include the effect of studs in addition to deck welds/screws/power driven fasteners.

 

[mark1234]

A while ago I compared the shear capacity values for composite decks and non-composite decks and came to the conclusion that...

The non-composite deck values are based on the failure of the metal deck itself. Just like a piece of plywood has published shear capacities.

The composite decks were based on the connection of the metal deck. The allowable shear values increased with the additional concrete and eventually hit a maximum with respect to gage and connection (weld or screw).


imnotclever: To answer your question, if you weld the studs through the deck and connect directly to the lateral member (i.e. wall, frame, etc.) you should be able to use the capacity of the stud and concrete.

These conclusions are based upon my assumptions and would appreciate others opinion.