A method to model wood by using ABAQUS finite element software. Part 1. Constitutive model and computational details

A structural analysis method for the long-term response of wood structures is presented in this report. This method has been developed with the finite element calculation software ABAQUS and its use requires - an effective computer - an ABAQUS licence - a Fortran licence compatible with the ABAQUS CAE version - the implementation scheme of the stress-strain relation for wood into the FE-program (UMAT subroutine for ABAQUS) - the implementation of the equation for moisture flow across the wood surface (DFLUX subroutine for ABAQUS). The forth and fifth components of the list above have been developed at The Technical Research Centre of Finland VTT. The material properties of timber in the grain direction and in the perpendicular-to-grain directions require defining a local cylindrical coordinate system for each piece of wood of the structure. The moisture transfer in wood is a function of the moisture flow on the wood surface and on moisture diffusion of wood. The response of wood to mechanical loading, moisture content changes and time was modelled by using a rheological model of wood implemented in a subroutine. The use of ABAQUS for detailed stress analyses of wood is demonstrated with examples