A novel approach for the identification of material elastic constants

The present study is part of an identifying programme for constitutive parameters in damaged materials, termed the "effective parameters". The programme starting point is that the experimental response depends not only on constitutive parameters, but also on structural mechanics and interaction with the test-machine. It is showed how the load-displacement diagram of compressed concrete cylinders is affected by crack propagation, through the resistant structure modification. Moreover, it is analytically demonstrated that the effective stress (sigma(eff))-effective strain (epsilon(eff)) curve exhibits a strictly positive derivative at the point corresponding to the average stress ((sigma) over bar)-average strain ((epsilon) over bar) curve peak. Finally, it is proposed a new identification procedure which provided satisfactory results, giving monotone strictly non-decreasing, size-effect insensitive and failure mechanism insensitive sigma(eff) - epsilon(eff) curves.