3D constitutive models for wood materials

Using wood as a construction material has a long tradition. Otherwise its material behaviour is subjected to many variable properties, so that it has still a lack of understanding. Moreover modelling its constitutive behaviour means to take into account its anisotropy, due to the cellular structure, and its nonlinear properties. Non-homogeneities, fibre-structures, porosity, are only part of the characteristics that a constitutive model should take into account. Reliable models are a necessary tool for the safety analysis of existing timber structures and for retrofitting. Two distinct types of approach can be recognized in contemporary researches in this field, the first based on the fracture mechanics, the second one developed in the framework of anisotropic plasticity. In this paper 3D constitutive model are analyzed, taking into account plasticity, large deformations, orthotropy and decoupled material directions, together with decay of initial elastic properties due to successive damaging phaenomena.