Plywood would be laying horizontally and be cut 8' x 8". Assuming fairly uniform load, with plates the full top and bottom length of it, is there a compression at which the plywood will fail? I'm assuming it would split or the glue would give at some point? But is this above 50,000 lb?
Wood – How much weight will 1/8″ plywood sustain for compression
plywood
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You defiantly need to support the subfloor around the perimeter.
Let's say this is your floor without plywood.
You want to put plywood down, but the edge of the sheet has nothing under it for support.
If you don't support the plywood, you'll end up with a "soft" spot around the perimeter. Stepping, or adding weight to this area will cause the plywood to flex. This flexing will cause the area to feel spongy, and could damage the flooring (depending on the type of flooring). To solve this problem, you have a couple options.
Blocking.
Installing blocking perpendicular to the joists will support the edge of the sheet.
The size and spacing of the blocking will be determined by local codes, so consult your local government for these requirements.
Additional Joist
Another option, is to install an additional joist to support the edge of the sheet.
This extra joist may not have to span the entire length, and may be able to be supported by blocking between the existing joists. Again, check with local building codes to determine what is required.
If those stringers are unsupported by an underlying structure such as a substantial mullion, it would allow unacceptable flexion at the joint under high wind conditions IMO. Even with a solid wood stringer you might have trouble over that long horizontal span.
Might I suggest that you use your idea but with the plywood in a vertical orientation? I know this would double the number of sheets required to 4 (5 to join with plywood "stringers"), but it would be much stronger this way. Also, the smaller pieces would be much easier to handle and install, and easier to store when there is no hurricane threat. 5 sheets is still way cheaper than a new window that size, you could use the leftover for other smaller windows.
Best Answer
You appear to mean compression perpendicular to the plane of the plies.
Depends a good deal on what the plywood grade and material is, and the conditions it's operating under.
http://www.g-lumber.com/pdf/APA_Plywood_Design_Specification.pdf Suggests that between 340 and 160 lb/in**2 for dry service and 105-210 for wet service (for grades appropriate to wet service) so you'll need a fair number of square inches (which you have inconveniently left out of your question) to support 50,000 lbs.
Looks like 476 square inches on the low end to 147 on the high end (of loading) though any sensible person would derate a bit more for additional safety factor, or use 1/8" steel as a shim rather than 1/8" plywood. That's 3.3 square feet to a bit over 1 square foot.
8 feet (96inches) by 8 inches = 768 square inches, resulting in a loading for 50,000 lbs evenly distributed of 65 pounds per square inch, so per the above document you should be safe at that loading.