Finite element models for nonlinear analysis of steel–concrete composite beams with partial interaction in combined bending and shear

The study in this paper compares three different beam models and relevant finite elements for the nonlinear analysis of composite members with partial interaction. These models are derived by coupling with a deformable shear connection two Euler–Bernoulli beams (only flexural deformability and flexural failure mode of each beam component), an Euler–Bernoulli beam to a Timoshenko beam (addition of shear deformability and shear failure mode for one component only), two Timoshenko beams (addition of shear deformability and shear failure mode for both components). Simply supported and continuous steel–concrete composite beams for which experimental results are available in the literature are used as benchmark problems. Aspects of the structural behaviour considered include: (i) effects of the shear deformability of the steel and slab components at various load levels; (ii) differences in computed collapse loads; (iii) differences in the internal actions, i.e. axial forces, bending moments, vertical shears and interface shear forces at different levels of loading. A study on the convergence rate of the finite element solution and considerations on locking-free finite elements are also presented. Results show that the three models present small differences when composite beams dominated by the bending behaviour are considered. On the other hand differences are significant for beams in which the interaction between bending and shear plays a substantial role; in these cases neglecting the shear behaviour in the composite beam model leads to considerably inaccurate predictions of the structural behaviour.