Static Bending Test of Timber Specimen

Theory of Bending: When beams are subjected to loads, bending stresses are set. The computation of this stress at a given section of the beam is facilitated by means of bending theory due to M. H. Navier. He postulated that under a uniform bending moment, initially plane and parallel cross-sections remain plane during bending and converge on a common centre of curvature. This can be visually demonstrated by drawing a square grid on a rubber beam (Fig.7.l (a)) and then bending the beam (Fig.7.1 (b)). Nevier's assumption has since been proved correct for all structural materials by strain measurements on test beams under load (Fig. 7 .2); strain gages are fixed at, say, each tenth of the depth of the beam, and the variation of strain throughout the section is plotted as the beam is loaded.