ENERGY-BASED FAILURE CRITERION FOR WOOD

Recent research into the strength of dimension lumber has led to the development of an alternative failure criterion based on the notion of a critical energy density for the material. The strength of wood is known to be related to the duration of an applied load; however, duration-of-load effects cannot be explained within the context of a theoretical failure criterion based solely on stress. Conversely, a theoretical relationship between ultimate stress and load duration can be demonstrated when an energy-based failure criterion is combined with a viscoelastic stress-strain model. In the present paper, the theoretical equations expressing the relationship between ultimate stress and load duration are derived for constant intensity loads. Two related energy-based failure models are proposed and investigated. Using available experimental data as a reference, a numerical experiment is conducted to compare the two energy models with a widely used. damage accumulation model.