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, numeric al simulations are subject to challenges. Shell finite elements are attract ive in these simulations. Rotational degrees of freedom do, however, compli cate the solution. In the present study a co-rotated formulation is employe d. The deformation of the shell is decomposed in to a contribution from lar ge rigid body rotation and a strain producing term. A triangular assumed st rain shell finite element is used. Hence, a high performance elastic elemen t is combined with the co-rotated formulation. In the co-rotated co-ordinat e system the plasticity is accounted for by a simplified Ilyushin stress re sultant yield surface. The stress update is determined from the backward Eu ler difference, and a consistent geometrical and material tangent stiffness is derived. Comparison with other published analysis results show that the present formulation gives acceptable accuracy. (C) 1999 John Wiley & Sons, Ltd.