What is Lug Angle
The lug angle is a small fraction of the angle used to connect the protruding part of the element to the gusset. The lug angle is designed to shorten the length of the gusset connection and reduce the effect of the shear lag.
A total of 8 bolts are required to make the connections in the picture. If all bolts are provided on the element only, the gusset length is greatly increased. Instead, I used three bolts on the corner ledges to shorten the gussets.
The rivets connecting the gusset to the edge are less loaded than the rivets connecting the main element to the gusset because the protrusion of the edge of the lug can be deformed.