ON THE LINEARIZATION OF THE MICROPLANE MODEL

The paper addresses the microplane model in the context of localizatio n analysis. Capable of reproducing experimental results of concrete sp ecimens, the microplane model includes anisotropic damage in a natural and conceptually simple and explicit way. However, the efficiency of former microplane implementations suffers from the expense of the solu tion procedure being based on the secant stiffness method. Within this paper, the macroscopic constitutive equation derived by kinematically constraining the microplane strains to the macroscopic strain tensor is consistently linearized resulting in quadratic convergence of the N ewton-Raphson iteration for the equilibrium equations. A fully three-d imensional model will be presented and linearized incorporating the tw o-dimensional case in a natural fashion. Furthermore, the localization criterion is analysed, indicating locally the onset of localization i n terms of the acoustic tensor. Several examples demonstrate the featu res of the microplane model in predicting the material behaviour of co ncrete in tension and compression as well as in shear. (C) 1998 John W iley & Sons, Ltd.