Development of enhanced fiber beam element with multi-axial material constitutive models for reinforced/prestressed concrete beams

• A new fiber beam element considering coupled flexure and shear is developed. • The new element can be used as a reliable numerical apparatus for concrete beams. • MCFT is integrated with the new element for concrete beams. • Shear capacity of concrete beams can be adequately predicted. In order to consider the interactive behavior of flexure and shear, an enhanced displacement-based fiber beam element is developed by utilizing multi-axial material constitutive models for fibers, in particular, with the Modified Compression Field Theory (MCFT) for fibers representing concrete with smeared stirrups in RC/PC beams/girders. The potential shear-locking problem is avoided by adopting a mixed interpolation form with a bubble term for the displacement field, and the validity of the approach is verified by a classic example. The proposed element is first validated through a classic test series of shear-critical RC beams from the literature and then applied to a PC girder recently tested under both shear-critical and flexure-dominated scenarios. It is shown that the proposed element can be used to predict the structural behavior of RC beams and PC girders satisfactorily, after enhancing the conventional fiber beam element by considering the coupling of flexure and shear. In addition, the proposed element provides a tool to predict both flexure and shear capacities of concrete beams with adequate accuracy.