Finite-Element Limit Analysis for Solid Modeling of Reinforced Concrete

Complex triaxial stress states are present in many reinforced concrete structures. These structures are often analyzed using simple hand calculations based on methods designed for plane structures. However, this can result in designs that are inefficient and excessive in material usage. This paper introduces finite-element limit analysis (FELA) for modeling of reinforced concrete structures, with separate modeling of concrete and reinforcement in a so far unseen scale. The method provides results for the capacity as well as the stress state and failure mechanism in the ultimate limit state. The FELA framework uses solid elements together with the modified Mohr-Coulomb and von Mises yield criteria. The framework uses a computationally inexpensive tetrahedral FELA element, which makes it possible to model rebar details in three dimensions (3D) with adequate discretization. The framework is demonstrated in two examples, one for verification and one showing the practical use of the framework by analyzing a tension connection with overlapping U-bars. The numerical results are compared with the failure mechanism and capacity from experiments.