Diaphragm fasterners 1

[Galambos]

considering a flexible metal roof diaphragm in a two span condition, simply supported, how are the fasteners designed over the interior support?

are they designed for 1/2wL for the joist spans on either side, and doubled up on the supporting line?

 

[JAE]

Not sure what you are asking. Fasteners of metal deck to supporting beams or joists are usually used primarily to resist lateral in-plane shear (diaphragm action) and vertical uplift due to wind.

Gravity loads are resisted by the bearing of the deck on the supporting member - that load doesn't usually go through or depend on the fasteners.

 

[Galambos]

perhaps, my question was poorly stated.

consider a long building with three braced frames, one at each end and one in the middle.

now with 300plf of lateral wind shear on one side of the interior braced frame and 300 plf of lateral wind shear on the other side, is the fastener spacing designed for 600plf over the interior braced frame?

 

[haynewp]

I think you are asking if the total lateral shear to be resisted at a single interior support line in a flexible diphragm is 0.5*w*L, where L is the length of the building?

If so; then yes and you would have to provide a total number of fasteners to transfer the total shear to the interior wall (you are referring to this as "doubling up" the fasteners to take the shear at each side of the wall).

It is confusing because you refer to the "diaphragm" and also to "joist spans", not sure if you are asking about lateral or gravity.

 

[haynewp]

You just beat me.

 

[Galambos]

thanks, haynewp,

silly question, i know, but i ask because i dont think ive ever seen anyone call out for 2x fastener spacing over an interior braced frame, but it came up recently.

 

[JAE]

Thanks Galambos for clearing that up.

haynewp - agree with you as well. Good answer.

 

[haynewp]

I have called them as "5/8 dia. puddle welds at 6" c/c, typ along the length of the interior support" or whatever it takes to get the total shear required to be transferred out of the diaphragm into the interior vertical element. Remember to include drags as needed.

 

[UcfSE]

I've always specified double lines as well.

 

[lkjh345]

Vulcraft's deck catalog, has Allowable Diaphragm Shear Strength tables that give allowable design values for shear transfer based on the deck's size, thickness, fastening, etc.

 

[DaveAtkins]

I understand what you are asking, and the answer is yes, the CONNECTION of the diaphragm to the interior braced frame (or moment frame, or shear wall) drag strut line must have twice the capacity of the DIAPHRAGM on each side of the drag strut line. It is best to use the same fastening throughout, however, to keep things simple.

DaveAtkins