The calculations provided above is a slap in the face. I made it too complicated and didn't see that 'PSI' is as simple as: lbs / in^2
When multiplied by the area of the rod (0.11 in^2 in this case), the in^2 cancel and you're left with lbs. Sometimes I over think things so much that I confuse myself.
To answer the questions everyone has. I went over this design with the mechanical engineers at work (I'm on the electronics side) to the point that one created a computer model to simulate bowing and stuff.
So the design is as follows: all the wood is slightly over 1" thick (I think about 1 and 3/16" - but labeled as 1.5"). The bookcase will have five shelves with sides (and a dado for each shelf) and open back. It will be about 45" wide, 12" spacing between shelves, and 11.25" deep.
Two threaded rods will go through each shelf with a washer underneath each shelf. From the computer model, the best is location for the rods is somewhere around 8" from each side (I have it noted somewhere - but going with 8" for purposes of discussion). So one threaded rod on each side, both being an equal 8" from the sides.
As for suspending, the threaded rods will go through the ceiling and into the attic where a 4" x 4" will be laid across about five joists. These joists are located on the load baring wall, so all the weight is transferred down to the basement steel posts. Most likely I'll put two or four screws into the wall just to keep the bookcase from pulling away from the wall (or shacking).
Hardware will be 70,000 psi stainless steel threaded rod, standard nuts, oversized washers under each shelf, and some aluminum plates (I have some spare pieces of aluminum) for washers on the 4x4.
I oversized everything. All the books I currently own weigh approximately 250lbs and doubt I'll add the same size large textbooks in the future (or even add another 100 or so books to make an additional 250lbs). In any case, I'm stating that the total weight (minus wood weight) will be 500lbs. Without looking at notes, I think 5/16" threaded rod is good for 2300lbs, so two will hold 4600lbs.
This 2300lbs is using 30,000psi as a safety margin (i.e. yield?
![Huh? ???](https://www.eevblog.com/forum/Smileys/default/huh.gif)
).