Size effect in concrete columns: Finite-element analysis with microplane model

Failure of concrete structures due to concrete failing in compression was r ecently shown to exhibit a size effect. This is not taken into account by c urrent design codes based on failure criteria expressed in terms of strengt h or plasticity. But compressive failure of concrete cannot be described by strength criteria, since it is brittle and is caused by release of elastic strain energy stored in the structure. In this sense, it is similar to ten sile failure governed by fracture mechanics. The paper presents a finite-el ement study of the size effect of compressive failure of geometrically simi lar concrete columns of different sizes. The test columns considered here a re reduced-scale specimens made with micro-concrete, of maximum aggregate s ize 3.35 mm and are loaded eccentrically. The analysis employs the micropla ne model for concrete. It is based on the crack-band concept and is shown t o capture with good approximation the size effect observed experimentally.