Finite-Element Analysis of Wood Joints

Abstract

A finite-element program to evaluate the stresses found in finger-jointed lumber subjected to uniaxial tension has been developed and verified. This program exploits a unique contact element useful in modeling a thin, isotropic boundary (glueline) between two anisotropic adherents. A parameter study was conducted using the aforementioned model to evaluate the influences of certain key finger-joint properties on the stress distributions induced in the lumber. Three joint geometries (step, scarf, and finger), three combinations of adherents (isotropic materials on both sides, orthotropic materials on both sides, and an isotropic material on one side and an orthotropic material on the other), and two glueline thicknesses (0.01 and 0.001 times the joint length) were studied. Glueline thickness is directly related to glueline stiffness, which is known to influence the stresses in the glueline, and consequently, in the adherents. The results showed that maximum adherent stresses were developed at the interface with the glueline. For isotropic materials with constant ratios of the elastic parameters between adherent and adhesive (e.g.,