Steel Collector Parallel to Deck - Deck Attachment

[Boiler106]

I have W16 and W8 collectors spanning parallel to 3 inch metal roof deck. Ribs are spaced at 8 inches oc, and are less than 2 5/8" wide. Low to moderate seismic zone (SDC B).

Other than specifying a member with a flange large enough to ensure its beneath a flute, i was curious what others have done to make sure the connection can be made.

Do you note that the deck is to be cut at fitted over top of the flanges? add a wide hot rolled or cold form top flange plate?

Im dealing with a factored diaphragm force of about 800plf.

 

[jayrod12]

Or have a plate added to the top of the W8 and W16 to ensure they'll be under a portion of the flute.

 

[BridgeSmith]

Why would you have beams running parallel to the decking flutes? The decking itself spans that direction. The collector beams and decking need to be perpendicular to each other, don't they? The ability of the decking to span perpendicular to the flutes is very small.

 

[Boiler106]

HotRod10, i have a 20k horizontal load from a construction hoist framing into the side of my 7 story building, perpendicular to a spandrel beam.

Im not concerned about my decking.

Collectors running parallel to decking is very common, although, usually they're girders.

This is also common at perimeter columns that take wind load, but dont have a girder framing into them perpendicular to the deck edge.

 

[BridgeSmith]

Ah, I think I get it. The hazards of not being familiar with the terminology, I guess.

Yeah, in that case a plate, as jayrod suggested, or possibly bars at discrete locations (depending on the necessary restraint capacity) may be the simplest solution. That could be tricky attaching them to the flanges, though, if there are fatigue stress concerns and the beams are continuous (if they're simple spans, no problem) . For bridge girders, we avoid transverse fillet welds as much as possible because of the big reduction in allowable fatigue stress range.

 

[KootK]

I like a C12 channel laid flat. If it needs a W8 or HSS welded to the underside, so be it. I favor square HSS with no possibility of LTB and therefor no need for additional bracing. 10" is enough to not have flute alignment issues on most 3" decks but the cost difference between C10 and C12 (common stair shapes) isn't worth worrying much about for this application in my opinion. Particularly with this kind of load, I wouldn't really want to mess around. Trying to get a 10" or 12" flange in a WF beam kicks you up into something pretty heavy imagine. It's bound to look a little weird broken by your regular, probably lighter roof framing members at 6' oc or whatever.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Boiler106]

since this was a field revision, I ended up with the following note, after talking to two different deck manuf engineers and detailers:

ATTACH DECK TO BEAM LINE W/ 5/8" DIA PUDDLE WELDS @8" OC, CUT DECK & ALIGN FLUTES, PROVIDE COLD FORMED INFILL PER MANUF AS REQD

They seemed pretty satisfied