Modelling cracking and bending failure of SFRC beams with conventional reinforcement

Paper in proceeding, 2013

In this study three beams, with varying contents of steel fibre reinforcement, were tested in four point bending and compared with results from FE-analysis. The beams were part of a larger experimental programme where relevant material properties were investigated. FE-modelling was performed using a two dimensional model. Concrete was represented by four-node quadrilateral isoperimetric plane stress elements. The smeared crack approach was utilized and the stress-strain relation describing the tensile behavior of the concrete was calculated from uni-axial test results, assuming the crack bandwidth to be equal to the element length. In compression, the concrete was assumed to behave elasto ideal-plastic. The reinforcement was modelled by straight 2-node truss elements connected to the concrete by two-dimensional interface elements providing the bond-slip properties. A material model including hardening effects was derived from tension tests of reinforcement bars and used for modelling the conventional reinforcement. A multi-linear bond-slip model was established through pull-out tests. As an alternative, analyses were also performed taking into account a reduction of the bond stress after yielding of the reinforcement occurred. Loading was applied in two phases: the first comprehending only the self-weight, while incremental loading was applied by deformation control during the second phase. General agreement between experiments and FE-analyses was obtained with regard to load-displacement behaviour. By observing the crack patterns, both from FE-analysis and experiments, it can be concluded that the general behaviour agreed; however, in the analyses not all cracks were fully localized. A higher degree of crack localization was obtained when the bond loss at yielding was included.