Bending Stress

Abstract

If a length of beam is acted upon by a constant bending moment (zero shearing force), the stresses set up on any cross-section must constitute a pure couple equal in magnitude to the bending moment. Hence it can be deduced that one part of the cross-section is in compression and the other part in tension. Referring to Fig. 6.1(a), subject to the condition that the end sections remain plane, it is clear that for an initially straight beam the inside or concave edge will be in compression and the outside or convex edge will be in tension. There will be an intermediate surface at which the stress is zero (“neutral” surface); the neutral surface cuts any cross-section in the neutral axis.