Perpendicular to grain stiffness of timber cross sections as affected by growth ring pattern, size and shape

摘要

A finite element plane stress parameter study of the global perpendicular to grain stiffness of timber structural elements such as beams and cross ties is presented. This stiffness is affected by the size and shape of the cross section, the growth ring pattern, the stiffness properties of the wood and the boundary conditions. Various rectangular sections with concentric circular growth rings with systematic variation of pith location were studied for elastic orthotropic wood properties corresponding to a softwood species and a hardwood species. Two conventional and two periodic boundary conditions were considered. The results are presented in diagrams. Growth ring pattern and cross section size were found to be of great importance for the stiffness, in particular for softwood elements. Global stiffness for material properties representing Norway spruce differed with a factor 7 between stiffest and weakest growth ring pattern. The influence of boundary conditions appears in comparison to be small.