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RE: Steel Deck Diaphragms

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Barry, I have had this same problem many times. Companies I been with have
researched the question and had some testing done. The results are not
perfect due to small test sample numbers but for comparison this is a good

Side lap fastening values for 20ga steel deck:
one inch long weld		1400lb
screw (any reasonable size)	 430lb
button clinch (no hole)		 120lb
clinch ( 30% hole)		  60lb
clinch ( 50% hole)		  25lb
The 'punched' fastener is very in inferior to a proper "button' clinch with
no hole.
The screw fastener originally specified is much superior to a button clinch.
The labour to provide clinches at say 8" centres compared with screws at 2'
makes the screws more economical, especially if you require clinches to be
doubled up when the clinch punches through. Screws are also much superior to
clinches in cyclic shear, therefore I use screws in all but the lowest
seismic zones and on any roof over a 5% slope. The clinch tool seems to be
very hard to use properly on a slope. I hope this will be of help.

Lorne Lapham, P.Eng 
Senior Structural Engineer
BC, Canada

-----Original Message-----
From: Barry H. Welliver [mailto:wellive(--nospam--at)]
Sent: Friday, April 23, 1999 8:11 AM
To: seaint(--nospam--at)
Subject: Steel Deck Diaphragms

I have specified a 22ga. steel deck  with puddle
welds at supports and #10 TEK screws at side laps.
The field has "supplied" a punched (button?) hole
at the side laps. My questions are:

1.    Is this crimped button hole comparable to
the TEK screws for side lap shear transfer?
2.    If so, is there available information
regarding substitution?
3.    Is this method (punched hole) considered a
stitch fastener?

Comments appreciated.

Barry H. Welliver