Shear and moment diagram

Summary

Shear and moment diagrams are the graphs of the shear force and of the bending moment along a beam. They are drawn from the loads and the support reactions by the equilibrium relations $V' = -q$ and $M' = V$. They show at a glance where a beam is most loaded, which is where it is designed or checked. The moment diagram is also the input of deflection methods such as Macaulay's method and the conjugate beam method.