Numerical simulation of reinforced concrete beam/column failure considering normal-shear stress interaction

•A concrete plasticity model is proposed for 3D fibre beam elements.•The concrete model deals with the interaction of normal and shear stresses.•The proposed concrete model accurately simulates shear failures of RC beam members.•Satisfactory predictions are obtained when comparing with short RC beam tests.

Fibre beam elements have vast applications to simulate the behaviour of reinforced concrete beam/column members. If normal-shear interaction is ignored, separated normal and shear constitutive laws are usually used in fibre beam elements, which is invalid to simulate shear failure in beam/column members with small or medium shear span-to-depth ratios. In this paper, a fibre beam element is treated as a degenerated solid element, and a unified concrete constitutive model is proposed for the degenerated solid element. Different from the separated constitutive models, the unified concrete constitutive model incorporates normal and shear behaviour based on three dimensional stress–strain states and, thus, normal-shear interaction is naturally considered. Moreover, compressive failure, shear failure and tensile failure are accounted for. Therefore, beam/column members with a wide range of shear span-to-depth ratios can be simulated with the degenerated solid element considering normal-shear interaction. Lastly, a variety of examples are presented to demonstrate the applicability and reliability of the proposed method by comparing numerical predictions with experimental results.