Nonlinear analysis of crack widths in reinforced concrete

Artikel i vetenskaplig tidskrift, 2009

Former research indicates that the crack width close to the bar can be a better indicator for the risk for reinforcement corrosion than, as current concrete codes impose, the crack width at the concrete surface. In this paper a finite-element model is used to increase the understanding of how the crack width varies at different levels from the reinforcement and how different mechanisms control this behaviour. Concrete and reinforcement are modelled with solid elements, where nonlinear fracture mechanics is used for the concrete material and a model, which has been modified for this purpose, describes the bond between steel and concrete. The results of the finite-element calculations of the crack widths are compared to earlier experimental studies. Both the finite-element analysis and experimental studies are performed on axially loaded concrete prisms with a central 16 mm reinforcement bar and concrete covers of 30, 50 and 70 mm. The finite-element analysis verifies the results from former experimental research, where the crack widths close to the reinforcement bar are affected only slightly, or not at all, by the concrete cover. This can lead to new possibilities of enlarging the concrete cover and increasing the durability of concrete structures in future.