1 1/2" roof deck - support at all edges?

[Ben29]

In the below image, imagine the steel beam aligns with the end of the roof deck. Do I need to provide a continuous angle, welded to the top of each joist, such to attach the metal deck to?

I have seen countless times when engineers do not provide an angle here to support the deck edge.

WHen I look at the SDI specifications, it reads, "Minimum edge attachment - Fasten perimeter edges of deck units at 36" maximum intervals or as shown on design drawings for diaphragm design."

Is SDI referring to the same thing that I am referring to?

 

[lexpatrie]

Yes.

Or rather, it's pretty commonly done.

The continuous steel angle runs parallel to the flutes and is welded to the joist seat where it occurs, for low enough diaphragm loads this will work out, for higher diaphragm loads that collector they show underneath is necessary, usually a C2.5 or an HSS 2 1/2" if you're concerned with gaps when it's attached to a steel joist girder, rather than a steel beam.

Note that those collectors aren't supposed to be shop welded to the steel as they're viewed as a tripping hazard in OSHA last I looked.

I love it I say something is "always" there then I open four goofy projects in a row where it's not there and finally find one in a more normal set of plans.

Also, I believe the Steel Joist Institute calls for it to be attached to the joists at a maximum of 18" o.c. (the metal deck).

See also Simple Connections Simplified, Holtermann, Martin, Steel Joist Institute, May 16, 2018, Slide 31-.

 

[BAretired]

The attached comes from the Canam Deck Catalog. A diaphragm needs a continuous chord to resist wl^2/8b where b is the width of diaphragm. It may not be framed exactly as shown in the diagram, but maximum connector spacing in the table should be followed.

 

[JLNJ]

Like so many things, the answer is, "It depends." This is why systems are engineered and not just rules of thumb.

If you don't have any diaphragm shear to transmit to the girder, then, no, no connector needed.
If you DO have diaphragm shear and the joists can take the rollover force, then, no, no corrector needed.
If you DO have diaphragm shear to transmit and the force exceeds the joist rollover capacity, then, yes, the connectors need to be designed, specified, and built.
If this is at a diaphragm deck edge and you have a chord force to activate, then, yes, you need connectors.

 

[lexpatrie]

If you DO have diaphragm shear and the joists can take the rollover force, then, no, no corrector needed.

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I don't think this is accurate, without the angle you are asking the metal deck to transmit a large concentrated force into the joist seat (diaphragm shear x joist spacing). There isn't much material here, so the ability to transmit load via a puddle weld alone is very limited. Let alone the potential for the deck to deform even if that load is transmitted.

 

[DaveAtkins]

I concur with the observations above. In addition, if you do not have an edge angle for the deck to fasten to, you should assume no sidelap connectors for the deck diaphragm capacity. I think this is part of the reason deck diaphragm tables have zero sidelaps per span as one of the choices.

DaveAtkins