Micromodelling and Macroresponse of Wood

A probabilistic model (named SIMWOOD) describing the non linear response and failure of glulam elements in tension is presented. The mechanical rules (failure criteria and redistribution rules) are detailed. Three sources of variability are analyzed : internal to clear wood, due to knots, due to finger-joints. It is shown how the inputs can be identified from experimental information obtained at the structural scale or at the material scale. Some validations of the model and the first results of computations are discussed. The interest of a non linear mechanical model is shown and it is demonstrated that (probabilistic) brittle models used at the structural level can highly underestimate the element strength. Size effects (length, depth and lam number effects) are discussed and some conclusions are drawn for building rules.