Microplane model for brittle-plastic material

ABsTRACT: A generalized microplane model 'or brittle-plastic heteroge-neous materials such as concrete, which describes not only tensile cracking but also nonlinear triaxial response in compression and shear, is presented. The constitutive properties are characterized separately on plane.s of various orientations within ' the material, called the mi-crop lanes, on which there are only few stress and strain components and no tensorial requirements need to be observed. These requirements are satisfied automatically by integration over all spatial directions. The state of each microplane is characterized by normal deviatoric and volumetric strains and shear strain, which makes it possible to match any Poisson ratio. The microplane strains are assumed to ~ the resolved components of the macroscopic strain tensor. The central assumption is that on the microplane level the stress-strain diagrams for monotonic loading are path-independent and that aU the path depen-dence on the macrolevel is due to unloading, which happens selectivel