FRACTURE SIZE EFFECT - REVIEW OF EVIDENCE FOR CONCRETE STRUCTURES

The paper reviews experimental evidence on the size effect caused by e nergy release due to fracture growth during brittle failures of concre te structures. The experimental evidence has by now become quite exten sive. The size effect is verified for diagonal shear failure and torsi onal failure of longitudinally reinforced teams without stirrups, punc hing shear failure of slabs, pull-out failures of deformed bars and of headed anchors, failure of short and slender tied columns, double-pun ch compression failure and for part of the range also the splitting fa ilure of concrete cylinders in the Brazilian test. Although much of th is experimental evidence has been obtained with smaller laboratory spe cimens and concrete of reduced aggregate size, some significant eviden ce now also exists for normal-size structures made with normal-size ag gregate. There is also extensive and multifaceted theoreretical suppor t. A nonlocal finite element code based on the microplane model is sho wn to be capable of correctly simulating the existing experimental dat a on the size effect. More experimental data for large structures with normal-size aggregate are needed to strengthen the existing verificat ion and improve the calibration of the theory.