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RE: Costco Structures

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Title: RE: Costco Structures

> Costco ... roof structure ... is clean, uniform, seemingly
>well designed, and it incorporates tapered plate girders/beams
>.... all the visible bolts seem to be about 1/2" in diameter. Even
>the connection of the beam flange to the column cap
>plate is made using small bolts. I am used to using 3/4" h.s. for every
>project except for heavy / long span structures where I use 1" A490's.
>Does anyone here use smaller diameter bolts routinely? Is there any
>rule of thumb on what structures it is more appropriate to go smaller?

I'm not sure about Costco's buildings, but your description makes them sound like metal buildings. If so, that fits with the use of smaller bolts because the metal building industry does use a fair number of them.

For conventional fabricated structural work, though, I'd recommend that you stick with 3/4-in. diameter as the usual minimum and 3/4-in, 7/8-in. and 1-in. as the preferred range of specified fastener diameter. It won't save much money to use smaller bolts, especially if the details become more labor intensive with more bolts and variations in connection detail. Besides, just about all design aids and tools available for use in design, fabrication and erection are set up for 3/4-in., 7/8-in. and 1-in., anyway.