et represents the area from the fastener center to the edge of the plate. It is is a simplified formula that makes it easy to understand the area. (e-d/2)t is the area between the nearest edge of the hole and the edge of the plate, but it is not a shear area since all shear load must move outward not inward. Lots of folks in industry use a more conservative area than et that represents the area from the hole 45 degrees from centef to the edge of the plate. It is conservative but is a good choice too
The force on the joint, often denoted P, is first axial in member, and is used for various strength checks. The magnitude may change for each check, depending on characteristics of the joint. This feeds checks for net tension, shear tear out, bearing, and fastener shear.
