Additional Weight and Concentrated forces are not the same thing:
The Concentrated Force command enables the user to define external forces and moments to be applied at the current point in each of the (global) X, Y and Z directions. Sets of forces and moments can be included in any available load case (if a load case did not previously exist, it is created upon acceptance of the dialog).
The Additional Weight command enables the user to define the weight (point load) of a nonstandard, or special component at the current point. The weight is automatically included in the gravity (GR) load case, and always acts vertically downward as specified in the General Model Options dialog (Vertical axis direction field ). Weight does not have to be defined at the pipe centerline.
Read AutoPIPE help for full details of each dialog.