Crack width simulation with discrete reinforcement and 3D nonlinear finite element models

Crack control is essential for the serviceability and durability of reinforced concrete structures. Until today a variety of crack width calculation models have been proposed, but there is still no generally agreed method provided in standards or literature. Overall, the existing models have different influencing parameters and even the relationship between experimentally measured, numerically simulated and analytically calculated crack widths is not clearly understood. Furthermore, the distinction between crack width at the reinforcement level and at the surface is controversially presented in the literature. This paper presents a detailed numerical finite element volume model for the simulation of crack opening in reinforced concrete that considers reinforcement ribs discretely. This aims to represent the complex stress state in the concrete near the ribs including the internal cracks. A parametric study is performed to determine the main factors influencing the crack width. Comparisons with experimental results show that the model realistically captures the crack width over the depth of the concrete cover. Additionally, comparisons with analytically calculated crack widths indicate that the analytical method based on displaceable bond primarily predicts the surface crack width. The difference between the crack width at the reinforcement level and at the surface is predominantly attributed to internal cracking whereas shear-lag deformations of the concrete itself are insignificant. The study also highlights the importance of distinguishing between the single crack and stabilized crack stages in crack width calculations and emphasizes the need to consider slip-dependent bond stress in analytical models.