Nonlinear Layered Timber Cylindrical Shells

The finite element method was used to model and analyze two cylindrical shells-one nail fastened and one glued-taking into account geometric and material nonlinearities. Earlier tests on the particular three layer membrane used for the shells provided values for the various elastic constants for both nailed and glued fastenings. In the case of the nailed fastenings, the in-plane shear stress-strain behavior was found to be markedly nonlinear while for the glued fastening the shear behavior appeared to be reasonably linear. In the case of the nailed shell, the exponential expression for the in-plane shear stress-strain behavior was adjusted in order to treble the shear stiffness. For the glued shell, parabolic and exponential expressions were fitted to the experimental shear stress-strain data in order to permit extrapolation; both expressions were suitable at lower loads but the parabolic one lead to considerable error at high loads.