Bending

In chapter 1 we introduced the concept of the bending moment. The effect of a moment is to produce curvature in a beam and to induce a system of bending stresses in the cross-section. If the moment is hogging, the top fibres of the beam will be in tension and the bottom fibres in compression. There must therefore be a layer in the beam where the stress due to the bending moment is zero. This layer is called the neutral layer and a line indicating this layer in the cross-section is called the neutral axis. In the theory that follows we shall consider a bending moment acting alone. This situation, in which both shear and axial forces are zero, is referred to as pure bending.