Non-linear analysis of composite beams by a displacement approach

The non-linear analysis of composite steel–concrete beams by the finite elements method permits obtaining useful information on collapse modalities but the convergence of the solution must be carefully controlled. Using the displacement formulation of the finite elements technique, the authors illustrate some aspects related to the convergence of the method by comparing solutions deriving from finite elements with 8, 10 and 16DOF. Some pathologies of the 8DOF element are posed in evidence.