The influence of shear and rotatory inertia on the free flexural vibration of wooden beams

The existence of shear and rotatory inertia effects leads to a reduction in the frequency of flexural vibration of beams as compared with the frequencies predicted by the simple Rayleigh treatment. Tables and graphs, based on the Timoshenko-Goens theory, are given to facilitate the estimation of the correction factor in the case of free-free beams. Experiments are described in which the frequencies of wooden beams are measured up to the 16th mode, and a least-squares method is described for analysing the results. Effects introduced by the anisotropic nature of wood are also investigated and discussed.