4-Node combined shell element with semi-EAS-ANS strain interpolations in 6-parameter shell theories with drilling degrees of freedom

A 4-node C-0 shell element with drilling degrees of freedom is presented in this paper. The element is developed within the nonlinear 6-field shell theory. Kinematics of the shell is described by two independent fields: the vector field for translations and the proper orthogonal tensor field for rotations. Within the theoretical formulation no restriction is applied on magnitudes of displacements and rotations. To avoid locking phenomena the proposed element combines two interpolation schemes: the assumed natural strain (ANS) for transverse shear strains and the enhanced assumed strain (EAS). The latter interpolation is used with asymmetric (in-plane) membrane strains. The performance of the element is evaluated by example of benchmark problems with special emphasis on shell structures containing orthogonal intersections.