Irontrussman
Structural
I work for a modular builder and we set the mods in place by lifting them with a cable that is 1/2 or 5/8 inch in diameter. The cable is threaded thru a hole drilled in the rim joists at the bottom of the mod. The rim joists are 2 plies of 2x12 SPF #1/#2. I've been charged with determining if we can use SPF(S)#2 without having the cables tear thru the rim joists. Each lifting point has approx. 9100 Lbs on the cable. I looked at the NDS yield limit equation I[sub]m[/sub] from table 11.3.1A, treating the cable like a dowel, but the calculated allowable "Z" value of 705 Lbs is way too low. In the mechanical world this would be a simple shear calculation with two resisting shear areas extending tangentially from the hole, perpendicular to the edge of the joists. But I haven't been able to find any published values on shear strength perpendicular to the grain, other than the crushing stress for bearings, which is limited to .04 inch of deformation (which is probably why the "Z" value was so low). Any suggestions.