Mixed Formulation of Inelastic Composite Shear Beam Element

Abstract

This study presents a new beam element formulation following a Hellinger-Reissner functional for composite members considering coupling between bond-slip and shear deformations. A robust state determination along with new stability criteria for the mixed-based formulation are proposed. The constitutive laws of the concrete, steel, and shear connectors are used to derive the inelastic coupled axial–flexural–shear interaction of the composite element. To consider shear deformations, Timoshenko beam theory has been adopted in deriving the section kinematics equations. The J2 plasticity following a radial return mapping algorithm and a fixed crack smeared softened membrane model are used to simulate the multiaxial stress state in steel and concrete, respectively. The accuracy and efficiency of the mixed-based formulation was evaluated by comparing the responses at local and global levels with the displacement-based formulation.