Shear thru thickness of plywood in plywood-timber I beam not computing. Shear thru thickness of plywood in plywood-timber I beam not computing. fastline12 (Aerospace) (OP) 1 Jul 16 01:55 Threaded deleted. We found what we needed. Thank you! RE: Shear thru thickness of plywood in plywood-timber I beam not computing. fastline12 (Aerospace) (OP) 5 Jul 16 21:51 OK, I guess we are back on this search so hopefully my previous delete is ignored. We are trying to calculate and predict design and ultimate load predictions for wood Ibeam construction with timber flanges and a single plywood web. We did some destructive testing of some in-house built I beams and seems our numbers were quite conservative and we are trying to pin a couple things down. Shear through thickness seems to be our biggest point of complication. Our predictions indicated a failure through the thickness but our tests were unable to induce this failure mode as roll shear took a front seat. We also held a LOT more load than what was predicted, indicating we may have some calculations wrong. Per the PDS manuals for shear thru thickness and thickness for shear, in both the main manual and the supplement regarding plywood-timber beams, these resources indicate a certain value for shear and thickness for shear. However, in another supplement for "all plywood beams", they indicate much different values for shear and thickness for shear, seeming to boost the thickness for shear by over 60%! Now if we were to apply those values, we might be much closer. However, I am still confused a bit as to why they are applying such an increase to shear capacity to an all plywood beam, but not a plywood/timber beam. They do include a stapling schedule for the plywood glued beams. We are using heavy nails in our Ibeams but documents seem to indicate to completely ignore their existence in the calculations even though there is certainly interaction there in helping to carry shear to the inner plies. Is anyone experienced enough in these areas to help point us in the right direction? We are mostly doing this as a research and learning experience right now, being fairly new to wood properties and behaviors.