Shear and moment diagram

The normal convention used in most engineering applications is to label a positive shear force - one that spins an element clockwise (up on the left, and down on the right).

Likewise the normal convention for a positive bending moment is to warp the element in a "u" shape manner (Clockwise on the left, and counterclockwise on the right).

In structural engineering and in particular concrete design the positive moment is drawn on the tension side of the member.

A convention of placing moment diagram on the tension side allows for frames to be dealt with more easily and clearly.

Additionally, placing the moment on the tension side of the member shows the general shape of the deformation and indicates on which side of a concrete member rebar should be placed, as concrete is weak in tension.