With the nail group calculation knowing the number of required nails, row spacing, nail spacing in a row one can come up with a rectangular approximation of the area filled with this group of nails.
The force applied to the worst case nail would:
F[sub]nail[/sub] = M[sub]joint[/sub]S[sub]x[/sub]S[sub]y[/sub]r[sub]max[/sub]/J
Where the Polar Moment of the Nail Group is given by J = bh[sup]3[/sup]/12 + b[sup]3[/sup]h/12: b = r[sub]x[/sub] + s[sub]x[/sub], h = r[sub]y[/sub] + s[sub]y[/sub]
s[sub]x[/sub] = nail spacing in x-dir
s[sub]y[/sub] = nail spacing in y-dir
r[sub]max[/sub] = distance from centroid of rectangle to corner (furthest fastener)
This won't be entirely accurate since the fasteners will probably not form a perfect rectangle but it should be reasonably close.
Then one can add this worst case nail force to the average force on the nails from an axial member load (conservative) and come up with the combined load on the worst case fastener.
This becomes an iterative process:
Step 1: Compute the number of fasteners for only the tensile load.
Step 2: Given the number of fasteners and fastener group geometry from Step 1 then calculate the load on the worst case fastener in the group.
Step 3: Add the value in Step 2 to average value from Step 1 and check against the allowable for the fastener. If it exceeds the allowable then add a fastener and repeat the computation of the average fastener load due to tensile load only and the load due to the moments, repeat until it passes.
It's no wonder that the truss companies have all of this stuff programmed. Technically this needs to be done for each joint at each load case, since load reversals may turn a compression loaded joint into a tension joint and vice versa, and the moments will be different for each load case.
As you can see engineering a truss (WGC or MPC) is no trivial matter.