Metal Deck Fasteners

[32romeo]

Does anyone know if there is a structural issue with button punching metal deck at the side laps? I had heard that it is not preferred (vs screws or welding) and decreases the integrity of the deck. Any comments appreciated. Thanks.

 

[jike]

If I recall correctly, the button punching method had the lowest of the diaphragm shear values for sidelap connections. They did not seem substantial as a welded or screwed nested connection. They have been dropped from the recent diaphragm tables. I assume that deck manufacturers no longer make the upstanding seam for button punching.

 

[enginerding]

The newest deck information that I have is from Vulcraft. They do not provide any diaphragm values for button punched sidelaps. What they do provide is diaphragm values for 0 sidelap fasteners that are shaded (at over 5'6" joist spacing). The footnote for the shaded area is as follows: "The shaded values do not comply with the minimum spacing requirements for sidelap connections and shall not be used except with properly spaced button punched sidelaps with 1.5BI deck."

 

[whyun]

I don't use button punched laps for bare deck diaphragms (non-composite deck), though it may be allowed at lower diaphragm shear capacities. In composite decks, I use button punched laps and use the concrete above deck for diaphragm capacity which is typically higher than bare deck with heavier lap attachment.