Appropriate Wood Constitutive Law for Simulation of Nonlinear Behavior of Timber Joints

In structural analysis, because of its anisotropic behavior, wood requires an appropriate constitutive law covering different behavior modes, such as ductile compressive behavior and brittle character in shear and tension. In this study, nonlinear material models were proposed to describe the behavior of timber in a finite-element method (FEM) model. An anisotropic elastoplastic constitutive law with hardening according to Hill yield criterion was used to describe the compressive behavior. Brittle behavior in tension and shear were modeled by using the progressive failure analysis approach, which is based on a failure criterion representing the evolution of damage in timber by a reduction of the elastic modulus. The wood material model was implemented in a three-dimensional FEM model to simulate the nonlinear behavior of timber joints with various types of loadings. The numerical model reliably predicted the stiffness and failure load of the joints. Furthermore, the failure index provided by the numerical model was used to evaluate the potential brittle failure position. Moreover, the initiation of damage and growth in timber members was modeled by using the element removal controlled by stress checking on the basis of the failure criterion. Good agreement was observed between numerical simulations and experimental measurements of failure modes.