FORMULATION OF ORTHOTROPIC DEGRADATION MODELS FROM DAMAGE- EFFECT TENSORS FOR PHYSICALLY NONLINEAR ANALYSIS

Resumo

In constitutive models based on the continuum damage mechanics, the process of material
degradation is described from damage variables that evaluate the nucleation and growth of micro voids

and microcracks in the medium. These variables can be expressed from tensorial entities called damage-
effect tensors, which is able to describe the material behavior considering, in the most general form,

anisotropic degradation. These entities are defined by a fourth-order tensor. This degradation approach
leads to a generalization of the deterioration process, since the secant tensor is obtained from a product
between the damage-effect tensor and the elastic tensor. This work presents a formulation of a continuum
damage model to deal with orthotropic material degradation, assuming different damage evolutions laws.
The degradation process is considered from damage-effect tensors for the physically nonlinear analysis
of concrete structures subjected to monotonic loadings. Different approaches of damage-effect tensors
presented on literature are discussed and implemented to validate this theory. The formulation was
implemented in the INSANE platform (INteractive Structural ANalysis Environment), a free computing
system developed in the Structural Engineering Department of Federal University of Minas Gerais.