Collapse of thin shell structures - stress resultant plasticity modelling within a co-rotated ANDES finite element formulation

Due to the very non-linear behaviour of thin shells under collapse, numerical simulations are subject to challenges. Shell nite elements are attractive in these simulations. Rotational degrees of freedom do, however, complicate the solution. In the present study a co-rotated formulation is employed. The deformation of the shell is decomposed in to a contribution from large rigid body rotation and a strain producing term. A triangular assumed strain shell nite element is used. Hence, a high performance elastic element is combined with the co-rotated formulation. In the co-rotated co-ordinate system the plasticity is accounted for by a simpli ed Ilyushin stress resultant yield surface. The stress update is determined from the backward Euler di erence, and a consistent geometrical and material tangent sti ness is derived. Comparison with other published analysis results show that the present formulation gives acceptable accuracy