Mesoscopic modelling of the behaviour of interfaces between reinforcing steel and concrete
Résumé
In order to predict the importance and distribution of mechanical damage in reinforced concrete structures, the modelling of the behavior of the interfaces between steel reinforcement and concrete is essential. It indeed directly influences the crack patterns. The commonly used interface laws incorporate parameters whose identification is generally based on pullout tests, for which sensitivity to a number of parameters is not fully explained. In this contribution, the steel/concrete interfaces are studied through a pullout test at the mesoscale, in order to gain a better understanding of the bond mechanisms. Numerical reinforced concrete samples are first generated by applying an adapted procedure. Each sample consists of homogenous concrete away from the steel bar and heterogeneous concrete that is divided into mortar and coarse aggregates in its vicinity. Finally, a ribbed steel bar is embedded in the concrete whose detailed geometry (especially ribs) is taken into account. Pullout tests are numerically performed using the finite element code Cast3M, on samples having different distributions of aggregates and different shapes of ribs, and using a damage model for the mortar. The steel/concrete interface is ruled by two different models: a linear spring model (LSM) or a modified cohesive zone model (CZM) based on Tvergaard approach. Their effects on the damage near the steel bar are especially studied. The response is analyzed in terms of damage patterns at the interface and the mortar, the force versus displacement curves, and the free displacement at the end of bar, in addition to some local quantities (normal and shear stress) along the bar itself. Moreover, the importance of including aggregates near the bar and the effect of their distributions on the behavior is investigated.