Structural members can be more than two-force, pin-connected members, like those encountered in a simple truss; they can have three or more forces and they can have fixed, as well as pinned, supports. The internal forces in a structural member can be more than tension or compression along the axis of the member. For example, a member might experience an internal couple moment.
In this tutorial, you will explore two-dimensional structural members with a coplanar force system. At a point CC in the member, the normal force NN, shear force VV, and couple moment MM need to be considered. The couple moment is also referred to as the bending moment.
Consider a long slender beam that has a rigid support at the left end and either a vertical or horizontal load on the right end. A point CC is located somewhere in between.