In reinforced concrete structures, the correct determination of the bond between concrete and reinforcement is a challenging task, as various mechanisms act simultaneously. However, the exact description of the geometry of the reinforcement is not possible when using Lagrange approach functions and can additionally influence the modeling of this interaction. The isogeometric analysis enables the exact representation of complex geometries and can thus improve the description of the composite behavior. Both the concrete matrix and the reinforcement are represented by means of their boundary surfaces in conjunction with NURBS and B-splines (SBIGA), which corresponds to the modeling technique in CAD tools. This makes it easy to use the design model in the analysis process. The interaction mechanisms between the reinforcement and the concrete are modeled using a thickness-free interface in combination with a thermodynamically consistent cohesive zone model that captures the decohesion, compression and sliding effects. It includes a coupled damage-plasticity dissipation for the normal and tangential directions.

The model was verified using test results. Furthermore, a comparison with the standard finite element method was performed to investigate the advantages of using isogeometric analysis for the accurate representation of the reinforcement.