Finite element analysis of timber containing branches – An approach to model the grain course and the influence on the structural behaviour

• Timber containing knots is investigated in structural analyses by means of FEM.
• Each knot is modelled geometrically and captured in the FE-model.
• A method to model the grain deviation in the area of branches/knots is presented.
• Timber boards are analysed in the elastic regime and beyond.
• Numerical results are compared to experimental results.

Wood, as a naturally grown material, is affected by growth inhomogeneities like branches. Especially in solid timber or glulam beams, knots lead to a decrease in stiffness and strength. In this contribution, approaches to model knots and the grain course in an FE-simulation are presented. Based on these methods, the influence of knots is evaluated by structural analyses. For validation, the numerical results are compared to experimental data. Since knots often initiate damage in structural timber parts, a failure criterion is applied in the area of the knots.