Before we introduce the idea of the simply supported beam and show the methods we adopt to determine the shear forces and bending moments in such beams, we will review and revise the fundamental concepts of static equilibrium and the principle of moments, which you may already have met but which are needed for any study of beams.
For a beam to remain in static equilibrium, two conditions must apply:
- The upward forces must equal the downward forces
- The sum of the clockwise moments (CWM) must equal the sum of the anticlockwise moments (ACWM).
You will know from Newton’s second law that ...