Wherever nails are located, there are two nails that attach the horizontal board to the upright boards.
Therefore, a pair of nails transmits the shear flow that exists in the highlighted area.
The shear flow that can be transmitted by two nails can be stated as:
The shear strength of the built-up beam must equal or exceed q = 198.53 lb/in. Using this value, solve for the spacing s:
