The document discusses reasons for sway in portal frames, including eccentric or unsymmetrical loading, unsymmetrical shape of the frame, different end conditions of columns, non-uniform member sections, horizontal loading on columns, settlement of supports, and combinations of these factors. It also describes using shear equations to evaluate joint moment or sway, which is an additional unknown for portal frames with sway. General and shear equations for different cases of portal frames with sway are presented.