On second though - unlikely that the deck will do anything but span between purlins, but the general question remains - do you count on deck running parallel with a member to brace the compression flange? Say in an edge beam?
You're the first licensed (I assume) person I've heard take that stance.
A company I had multiple interviews with and ultimately a job offer from gave me an 'engineering test' which, among other things, involved sizing a beam. I sized it larger than the Manager with whom I reviewed the test did, finding that LT buckling would control. He informed me that I was wrong because the parallel ribs did indeed brace it.
Most engineers at my current office take the same stance, although it's a condition that comes up more in conversation than in actual projects.
Assume you have a edge girder spanning 30' with beams framing in at 5' o.c.
The deck (no topping) will get attached to the beams with puddle welds (typically) and also to the edge beam with puddle welds (typically).
There is an argument to be made that this panel which is rigidly attached to the beam and girder will offer the required flange brace force. I haven't come across any myself.
CSA S16-01 Article 9.2.7 stipulates that the deck must resist a force equal to 0.05 times the maximum force in the flange or chord. The force may be considered uniformly distributed along the length of compression flange or chord.
VTEIT- read through slick's referenced post, I didn't need my mind changed, but I wonder if it would change you or your coworker's minds... A deck perpendicular to the deck flutes in my mind has very little in-plane compressive strength. It would most likely fold like an accordion with most common gauge sizes. Think about it on a micro-level, one rib, this is like a cranked-moment-frame made out of very thin steel with little bending strength... Luckily when deck ribs are parallel to a beam in most instances there are beams perpendicular to, and bracing, the girders.
Its amazing how much beam bracing is brought up as a topic on this message board. Maybe AISC should do a webinar or technical article or something specifically on this subject and address several common situations and methods of bracing.
a2mfk - my mind doesn't need to be changed - I'm of the opinion that even using the '5% rule' for which BAretired actually sited a source, parallel ribs won't provide that. As mentioned, a slab poured on that deck will. So we're on the same page.
The reference thread was a good read though - thanks.
