A mechanical model for compressed concrete in R/C beams

The distribution of stress in the compression zone of R/C beams subjected to flexure is usually computed by means of uniaxial stress-strain relationships. When crushing of compressed concrete occurs, the effect of curvature (or strain gradient) becomes important and uniaxial stress-strain curves are no more representative of physical evidence. To overcome this difficulty, in this paper crushing of concrete is modelled by means of sliding planes, which allow the expulsion of v-shaped concrete blocks. The mathematical description of the mechanical behaviour of this sliding phenomenon leads to a stress-strain relationship for concrete with a particular softening branch whose shape depends not only on the applied curvature but also on the dimension of the damaged zone.