Polebarn loft

Just finished having a 16' high 40'x40' addition built on to an existing polebarn. I wanted to build a loft over 1/2 of the addition for storage. Want to design for a 100lb/sqft liveload. My plan was to duplicate the endwall poles placed on 8ft centers with doubled 2x12 plates to rest 20ft engineered lumber joists on 16" spacing covered with 3/4 t&g plywood. Does anybody know of a link to get the loading and span distance for engineered lumber or better yet if my design will get me to my live loading target.
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Jeff-
A couple comments....
First I think I understand your framing system.
By 2 x 12 "plates" do you mean "header"?
The 2x12 double headers would span between the poles & the 20 ft joists would span between the headers?
If so.... a back fo the envelop calc tells me that the 2x12's are undersized; you're asking them to carry about 1200 lbs per ft.
You CAN go 20 ft @ 100 psf with engineered timber but I'm guessing you'll have to go with a 14" deep joist AND drop to 12" oc spacing. The 3/4 T&G is of course fine.
But as everyone always says "you should have this engineered by a local guy"
for span tables (actually these tables don't go to 100psf, need to be be calc'd) go to www.apawood.org & reigster (its free)
& download I joist publication
APA Performance Rated I-Joists Includes information on Span Ratings, installation details, cantilever designs, architectural specifications and engineering design properties for APA Performance Rated I-Joists. Only available as a downloadable pdf file. Revised April 2004. (Form Z725 - 22 pages)
cheers Bob
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Thanks for the reply Bob, yes headers instead of plates and you've correctly figured out what I was trying to describe. Thanks for the link regarding span tables. Any idea where I would find the rest of the reference material to size & space properly everything I want to do. I wanted 100lb/sqft because I plan to store several (15-20) jukeboxes in this loft and they average 350lbs each.
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