Non-Composite Metal Deck Attachment Using Screws

[whyun]

Traditionally, metal decks have been attached to steel support members which resist wind uplift (at roof) and diaphragm shears from lateral forces. In more recent times, screwed decks are becoming more and more popular due to much easier installation.

There are a few ICBO reports (ICC Reports) with tested capacities of such systems.

My question is, what is the impact in the diaphragm shear capacities if the supporting steel members are very thin (such as in cold formed metal joist system, say 16 to 14 gage joists at 24" to 48" o.c.)

Reference document is ICBO ER-3056 which talks about support steel thickness range of 3/16" through 1/2".

 

[Lutfi]

I for one like to use the screwed deck method for many reasons and here is a list:

1. Many times the welders do poor job in puddle welding due to the position.
2. Often the welders burn through the deck around the puddle weld that is not favorable.

3. Welding destroys the galvanized finish on the deck that makes easy place for corrosion to start.

4. Welders miss the joists or do not place 100% of puddle weld on joist or truss top chord and it is hard to verify the contact area.

The only shortcoming of screws is the diaphragm shear strength is not as high as one developed by welding.

One good source for screwed deck pattern capacities in manual published by the deck institute and which is based on Dr. Larry Luttrell's research at West Virginia University.

Regards,


Lutfi

http://www.cdeco.com

 

[whyun]

Thanks for sharing, Lutfi.

I was interested in limitations on the base steel member thickness.

ICBO report ER-3056 has a bunch of values for various deck thicknesses and screw patterns. But way it reads led me to believe that screwing to a very thin material (such as metal joists) is not included in their testing.

Any further thoughts? Thanks in advance.

 

[Lutfi]

I am at home now but I will look up some of the material that I have in the office and will let you know what I come up with.

In the past I used screw patterns on light gage metal trusses with good success.

Regards,



Lutfi

http://www.cdeco.com