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metal deck fasteners
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.
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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.
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."
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.

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