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SUMMARYThis paper presents the finite rotation exact geometry (EG) 12-node solid-shell element with 36 displacement degrees of freedom. The term 'EG' reflects the fact that coefficients of the first and second fundamental forms of the reference surface and Christoffel symbols are taken exactly at each element node. The finite element formulation developed is based on the 9-parameter shell model by employing a new concept of sampling surfaces (S-surfaces) inside the shell body. We introduce three S-surfaces, namely, bottom, middle and top, and choose nine displacements of these surfaces as fundamental shell unknowns. Such choice allows one to represent the finite rotation higher order EG solid-shell element formulation in a very compact form and to derive the strain-displacement relationships, which are objective, that is, invariant under arbitrarily large rigid-body shell motions in convected curvilinear coordinates. The tangent stiffness matrix is evaluated by using 3D analytical integration and the explicit presentation of this matrix is given. The latter is unusual for the non-linear EG shell element formulation.

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