Thanks to Tim and Chris for your suggestions and concerns. I'd appreciate anyone who wants to check thru this stuff to question it! I have used both tables from the books and stress equations as a double-check. I didn't explain the configuration very well. There are 8x8 beams supported on 8 foot centers. The maximum distributed load on a beam is 7040 pounds with a 6000 pound truck right over a beam. I picked the 8x8 from Tables and also by doing the stress (Modulus of Rupture) equations to see the safety factor for a load and beam sizing.
The pockets for the joists are 4" wide, 5" high and only 2" DEEP into the beams. So, taking a worst-case approach where the remaining beam is only 6" wide and 8" high, the numbers come out like this:
Experimental section : Calculation : (Evenly distributed load)
Load lbs 7040.00
Length (in) 92.00
Width Beam (in) 6.00
Depth Beam (in) 8.00
Calculated MOR (psi) [less than 1600] 1265.00
(The 1600 PSI is with a 4 to 1 safety factor (Will be 6 to 1 safety factor when dry). So it's only at 1265 PSI even with a 6x8 beam, and that looks fine. I agree that my original idea of compensating for the loss of material by wedging, although mentioned in a couple of books, is not very controllable, and I won't rely on it.
The 'checkerboard' configuration does mean that there is only ONE set of pockets in one side of any beam. Take a look at some photos at:
http://terryking.us/public/barn/floorframe.htm to see how this works (click on photos to enlarge).
The joists fit VERY tightly into the pockets (See jig photo) although as Chris points out the compressive strength perpendicular to the grain is only about 1/3 that along the grain. And they'll shrink more in that direction.
OK, the joist sizing is similar: on 2 foot centers the maximum load (1 wheel right on a joist) is about 1500 pounds. The 2" flooring will distribute the load significantly. The stress with 1760 pounds on a 4W by 6H joist is 880PSI, way under the 1600 PSI max I'd want to go.
The next part is the flooring (NOT tongue-groove) and the smallest plank is 8" x 2" (I have 10" wide in the obvious wheel track areas, for even more safety factor). Because of the wide beams and joists, the unsupported space is only about 18". I checked 18" and 19" like this:
1st Floor Floorboard calculation: center load. 1 wheel!
Load lbs 1500.00 1500.00
Length (in) 18.00 19.00
Width Beam (in) 8.00 8.00
Depth Beam (in) 2.00 2.00
Calculated: 1265.63 1335.94 MOR (psi)(Should be 1600 or less)
In the photos you can see one bay that has a removed "pit" area for vehicle repair. I've parked the truck there, and seen no movement of anything and no creaks, etc. at all. Rain stops and I'll have it out on the main deck so I can use my crane for the last 4 beams, and finally get to building UP a barn...
Anyway I've learned a lot from this whole discussion, and gone back over the numbers on every beam and post and joint in the rest of the design. And I checked the PSI in each joint, for both side compression where ends sit on posts, and lengthwise loading.
If anyone's Math Happy, I can put the Lotus 123 spreadsheet I have with all the calculations up on the web. Also, someone asked about the jigs... oh, that was over in a different router discussion; I'll go there for that.
I'll put up a photo of the truck ON the deck, hopefully on the TOP, in a couple days...
Read My Lips: No More Wedges...