Problem 8.5

 

Given

4x8, 5-ply plywood panel

spans roof joists, 16 in. OC

 

Weak direction means the 8-ft dimension runs parallel to the joists.  (see textbook figure 8.4, page 8.9)

The plies that would support a sheathing load are the crossband plies, because the wood grain in these plies runs parallel to the tensile and compressive bending stresses that the panel would experience.  The center ply would be at the neutral axis and therefore have little or no bending stress.  The grain in the face and back plies would run perpendicular to the bending stresses and therefore not be able to support as much load.