Finite Element Modeling of Wood Diaphragms

Abstract

This report describes a two‐dimensional finite element model for analyzing vertical and horizontal wood diaphragms. Central to the development of this model is the formulation of a nonlinear finite element that accounts for the distribution and stiffness of fasteners connecting the sheathing to the framing. Linked with conventional beam and plane stress elements, which represent diaphragm framing and sheathing, respectively, the resulting model can be used to analyze a variety of wood diaphragms (walls, floors, ceilings, etc.). Load‐displacement results from experimentally tested diaphragms and model predictions were found to be in good agreement. Parametric studies with the model show that diaphragm stiffness is significantly affected by nail stiffness, nail spacing, and the use of blocking. At code allowable diaphragm shear load levels, a variation of 20% in nail stiffness resulted in a change in diaphragm stiffness of less than 10%. Nail spacing was shown to have a more dominant effect on diaphragm stiffness than nail stiffness.