Metal deck bucking due to compression from lateral load transfer from wall studs? 1

[abusementpark]

Does anyone here know how to calculate the buckling capacity of a metal deck due to an in-plane compression load?

I am thinking about the common scenario where lateral load on wall studs is transferred along the roof edge thru the connection of the metal roof deck to the edge beam. For typical floor-to-floor heights and beam/joist spacings, we assume that the load gets transferred without locally failing the deck in the compression, but there must be some limit. For example, what if the wall studs are spanning >25' with a large parapet and the beam spacing on the roof is >10'. The force transferred becomes much more significant and the larger beam spacing increases the "unbraced length" of the deck. I start to get concerned about the deck capacity.

Has anyone found a way to check this?

 

[nicoga3000]

All of my decking design resources are at the office, but I would imagine one way you could do this is to treat the decking as a pinned column. You have your section properties of your deck and should be able to determine the buckling strength from that. You make a good point, though - I'm not sure in-plane compression/tension loadings are covered in any of my resources. The only in-plane loading condition I know I have material for is for lateral support strength.

You MIGHT investigate THIS document by Helwig and Frank. It discusses in-plane forces and I've used it extensively for bracing large span beams. The geometry of that fluted system is very strong (see fluted pillar water towers), and we design those somewhat regularly where I work. It would still be very interesting to see what sort of capacity the decking would have in the situation you're proposing.

 

[JAE]

A few fellow engineers and I once did some calculations for this assuming the deck flutes were parallel with the direction of loading so a single deck flute was used as a pin-pin column much like nicoga3000 mentions. We used the deck section properties and neglected local buckling and found that the typical deck (18 to 22 gage - 1 1/2" deep - 4 to 6 ft. span to the first interior roof joist) could take quite a bit of load.

Despite this, I've always felt uneasy about using gage metal to resist lateral loads from a building wall. We typically add steel struts (channels) within the flutes and welded to the next interior joist, allowing the deck to also weld/screw to the struts to soften the loading on the deck and reduce the non-redundancy of the deck taking everything.

 

[sandman21]

I believe SDI and AISI both have design examples for deck compression.

Yes you will get very high loads if you check the section proprieties, this however does not that into account the failure of the fastener at the seams. Depending on the deck you can get about 1 kip per foot in the strong direction

 

[sandman21]

Check your deck based on AISI S100-2007 C4 to determine the allowable loads.

Steeltools has a spreadsheet for determining the axial capacity of vulcraft deck, search for Roofdeck.

 

[Gumpmaster]

Verco Deck has some tables and example calculations which show this. They don't publish them, but if you ask their engineers, they will provide you a copy.

 

[RFreund]

You are referring to the local compression load from the wall (compression parallel to the wind direction) right? Not the compressive stress associated with bending and the beam analogy (fb=Mc/I) right?

EIT

http://www.HowToEngineer.com

 

[KootK]

An issue complicated by the fact that the deck is usually acting as a beam-column.

I'm curious about your detail JAE. It sounds like it's a channel with ~1.5" flanges laid flat beneath the deck. Is that correct? Do you take much flack from contractors over installation difficulties? I've tried to do something similar for other reasons in the past and received a far bit of push back. The channels go in after the deck is installed, right?

 

[beemer218]

You could use the RSG light gage steel software (free demo) to analyze a section as a pinned column with axial load.

 

[abusementpark]

Thanks for the help guys!