Roof metal deck allowable lateral deflection-Wind

[JoeBaseplate]

What are the limits for horizontal/lateral deflection of metal deck under wind loading? I am checking to see if a 1.5x22 Ga deck is OK for use. Using the vulcraft deflection formulas I am coming up with 1.5” deflection at the center. The roof line height is 31’ and the walls are precast. In the past I have used 2h/600 for masonry walls but I think I should be able to use higher number for precast.

Thank you.

 

[JoeBaseplate]

Question #2: I noticed that for the same gage deck, say 20 gage, when I try to determine deflections using 4’-6” & 5’-0” oc joist spacing, I am actually getting a smaller deflection using the larger spacing.

With W= 463 plf @ 4.5’ (k1 = 0.352, K2 = 1056, Db= 1652….36/5-1 side lap) I am ending up with 0.95” deflection on a 99’x67’ roof.

Now using 5’ joist spacing (K1= 0.242, K2 = 1056, Db= 1652….36/5-2 side lap) I end up with 0.85” deflection.

Shouldn’t the deflection be less for the smaller joist spacing?

 

[SteelPE]

Is this for deflection of the diaphragm under wind loading.

For industrial type structures I usually defer to AISC Design Guide 7 written by Fisher. He makes recommendations for serviceability is chapter 10 of this manual.

 

[JoeBaseplate]

Steel,

Thanks for the reference and yes I mean lateral deflection under wind. I did look thru that particular chapter it appears that for precast wall panels the drift limits is h/100. Seems a little too liberal to me.

 

[SteelPE]

At least you have something in writing. I believe this was for industrial/mill type structures and I am not sure if it would fit your case.

I'm sure others will have opinions as well.

Inside my AISC design guide no 3 I have a stapled set of pages from Engineering Journal/ American Institute of Steel Construction First Quarter /1993 that lists a limit of H/200 for precast panels for "Wind Frame Deflection". Maybe you could look in there for some more information.

 

[SteelPE]

Any luck with the engineering Journal?

 

[JoeBaseplate]

Steel, no haven't found anything yet. I asked a precaster if he has any input on the issue. Will post the response if I hear back form him. But since I have used 2h/600 for masonry walls in the past (a number that came from my old boss) I am thinking of using something like 2h/500 which amounts to 1.5" for roof level @ 31'.