Concentrated Load on Metal Deck

[RFreund]

Is there a procedure to determine the effective width of a roof deck subject to point load (say a ballast tray for example)?

I thought I had found one at one time, but can't seem to find what I was looking for.

Thanks!

EIT

http://www.HowToEngineer.com

 

[CURVEB]

Try the ICC report maybe?

 

[KootK]

Given the nature of deck, it's hard to imagine that you'd get much distribution beyond the loaded surface. It's really no better than flat plate stock in the direction perpendicular to the flutes. In fact, it's worse because the corrugation makes the deck length effectively longer. Maybe one flute beyond the loaded area on each side? If you want this badly enough, it would be relatively straight forward to model in SAP etc by accounting for the flexural anisotropy in your property modifiers.

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.

 

[RFreund]

by accounting for the flexural anisotropy in your property modifiers

You are referring to modifying the I.x and S.x values, etc. for each direction?

I was thinking that you would mostly likely get the width of the piece of deck (I think typically 36"). hmm....

EIT

http://www.HowToEngineer.com

 

[KootK]

You are referring to modifying the I.x and S.x values, etc. for each direction?

Yesir. If you do this, I want to see the results.

I was thinking that you would mostly likely get the width of the piece of deck (I think typically 36")

I'm looking up at exposed deck as I type. If you only loaded one flute at the edge of a 3' sheet on a 5' span, I very much doubt that you'd get meaningful participation from the flute on the other side of the 3' sheet. I don't know how to evaluate that, however, short of conducting the modelling exercise.

The shear connections between sheets seem to always occur at or near vertical flute legs. As such, I feel that shear could be transferred across multiple sheets nearly as well as it could be transferred within 3' sheets. Following this through, that suggests that you may not be limited to just the loaded sheet. That's just my gut feel however. If this was my baby, I'd be tempted to just use the loaded flutes.




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.

 

[RFreund]

I don't have SAP, but maybe this can be done in Staad Pro. Possible model a plate with the equivalent properties, although I'm not sure if the weak direction properties are available.

I'll let you know if it goes there.

EIT

http://www.HowToEngineer.com

 

[rlflower]

Check the roof deck manufacturer's catalog and the mfr's technical rep for their recommendations. This sounds like a common problem that they may have already addressed to their satisfaction at least.

Richard L. Flower, P. E., LEED Green Associate
Senior Structural Engineer
Complere Engineering Group, Inc.