High Capacity Metal Deck Diaphragms

[bigmig]

Are there any tricks to bumping up the allowable psf in a non composite metal deck for diaphragm shear load transfer?

Has anyone ever used two layers metal deck, layed right over each other? Is there some special weld pattern or type of deck? I'm trying to use a 1.5 type B.

We have a project with relatively small area of the oveall roof diaphragm bordered by diaphragm openings (clerestories)I have a flexible, irregular diaphragm attached to a masonry shearwall in this location.

I would love to keep the same gauge deck everywhere althouh even with the heavier guages and tigher joist spacings I'm having problems falling under the allowables given in the metal deck supplier's design book.

 

[OHIOMatt]

Have you looked at specific manufacturers such as Verco (I believe that they were purchased by Vulcraft a couple of years ago)? They have a proprietory side lap fastening system as well as some deck stiffeners.

I have used the products in the past for decks with up to 1200 plf of shear.

 

[bigmig]

What is a "deck stiffener"? I'll check out Verco.

Thanks.

 

[OHIOMatt]

Verco's is call Sheartranz. It basically goes in the flutes of the deck to elimnate or greatly reduce buckling as a failure mode.

The attached file is from the ES report from Verco

For capcities, you will want to look at ICBO ES Report-ER2078

 

[DHKpeWI]

Be careful about using the shear values in the deck suppliers catalog. There are different Omega and Phi values (factor of safety) for wind and seismic loads. The Steel Deck Institute publishes "Diaphragm Design Manual" Third Edition that has shear values for various deck types and gages and various weld patterns. I highly recommend this resource.

http://www.sdi.org/manuals.htm

I assume you are aware that increasing the number of welds or intermediate fasteners will increase the allowable shear values. However, it is not clear whether the welds or the deck are controlling the design, so I am not sure how to quantify the capacity of two layers of deck. Just a thought; perhaps you could use two layers of deck with a 36/7 weld pattern and take double the value of a single layer with a 36/4 weld pattern.