Evaluation of Shear Web Ply Orientation for Wood I-Beams

Four arrangements for the web plies of a wood I-beam are evaluated to obtain the relative strengths of the alternative configurations. The finite element method is utilized for the analysis to allow the idealization of orthotropic material behavior and other details of the uniformly loaded beam with two equal spans. A closed-form solution for the I-beam is developed to check the finite element solution. This formulation is based on the theory developed by Von Karmen and Seewald for the analysis of beams with a rectangular cross section. The results are also compared with the engineering theory of bending. The stress contours obtained from the finite element analysis are utilized in conjunction with an adaptation of the Henkey-Von Mises failure criterion to predict gross section failure. The results indicate that increasing the number of web plies in which the longitudinal grain axis is perpendicular to the horizontal axis of the beam increases the mean relative strength of the I-beam.