DAMAGE, GRADIENT OF DAMAGE AND PRINCIPLE OF VIRTUAL POWER

A theory of continuum damage mechanics is developed within the framewo rk of the principle of virtual power. Because the damage in a solid re sults from microscopic movements, we decided to include the power of t hese microscopic movements in the power of the internal forces. The mi croscopic velocities are related to the damage rare. The power of the internal forces we choose depends on the damage velocity and its gradi ent to take into account the interactions. Models issued from this the ory are presented. They are coherent from the mechanical and mathemati cal points of view. The numerical computations show no mesh sensitivit y. They describe with good agreement the main experimental properties. Concrete is chosen as an example to illustrate the theory. A model us ing two damage quantities is also presented. It yields the correct des cription of the unilateral phenomenon observed in concrete. Finally, a n extension of the existing models is proposed to describe the fatigue damage behaviour.