Summary

In this paper a nonlinear sectional formulation to account for full 3D stress' strain states on frame elements is presented, by means of a special cross-section model which allows for warping and section's shape distortion. This formulation allows using a 3D constitutive model for concrete. Subsequently, the approach is applied it to the nonlinear coupled behaviour of RC sections under multiaxial internal forces considering inclined cracking pattern and failure stages. The applicability of the model to RC sections is validated by means of combined tangential-normal loading case studies. The presented formulation uses the traditional six generalized strains 3D sectional analysis; therefore it can be implemented on any 3D frame element without introducing additional degrees of freedom on the frame element.