Mesoscopic study of concrete II: Nonlinear finite element analysis

Abstract

At mesoscopic scale, concrete may be regarded as a three-phase composite consisting of coarse aggregate, mortar matrix and interfacial zones. Its composite behavior can be studied by generating a random aggregate structure which resembles the mesoscopic structure of concrete and analyzing the interaction between the three phases using the finite element method. A method of generating random aggregate structures taking into account the size, shape and spatial distributions of aggregate particles has been developed and presented in part I of the paper. Herein, a nonlinear finite element method suitable for mesoscopic study of concrete is developed. Goodman type interface elements are used to model the interfacial zones. Cracking and nonlinear constitutive properties of the materials are taken into account. A failure criterion combining tensile strength and fracture toughness is adopted. Stress relief as cracks propagate is also allowed for. An adaptive incremental displacement controlled iterative scheme which can deal with post-peak behavior is employed. The method is applied to study the strain localization of concrete under uniaxial tension in a numerical example.