An isogeometric Reissner–Mindlin shell element based on Bézier dual basis functions: Overcoming locking and improved coarse mesh accuracy

• Published in: Computer methods in applied mechanics and engineering Vol. 370; no. C; p. 113283
• Main Authors: Zou, Z., Scott, M.A., Miao, D., Bischoff, M., Oesterle, B., Dornisch, W.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2020; Elsevier BV; Elsevier
• Subjects: Accuracy; Basis functions; Bézier extraction; Computation; Dual basis; Geometric accuracy; Isogeometric analysis; Locking; Membranes; Mindlin plates; Orthogonality; Reissner–Mindlin; Shells; Thin wall structures; Isogeometric analysis; Shells; Bézier extraction; Dual basis; Reissner–Mindlin; Locking
• ISSN: 0045-7825; 1879-2138
• DOI: 10.1016/j.cma.2020.113283

We develop a mixed geometrically nonlinear isogeometric Reissner–Mindlin shell element for the analysis of thin-walled structures that leverages Bézier dual basis functions to address both shear and membrane locking and to improve the quality of computed stresses. The accuracy of computed solutions over coarse meshes, that have highly non-interpolatory control meshes, is achieved through the application of a continuous rotational approach. The starting point of the formulation is the modified Hellinger–Reissner variational principle with independent displacement, membrane, and shear strains as the unknown fields. To overcome locking, the strain variables are interpolated with lower-order spline bases while the variations of the strain variables are interpolated with the corresponding Bézier dual bases. Leveraging the orthogonality property of the Bézier dual basis, the strain variables are condensed out of the system with only a slight increase in the bandwidth of the resulting linear system. The condensed approach preserves the accuracy of the non-condensed mixed approach but with fewer degrees of freedom. From a practical point of view, since the Bézier dual basis is completely specified through Bézier extraction, any spline space that admits Bézier extraction can utilize the proposed approach directly. •A mixed Reissner–Mindlin shell is developed to overcome locking and improve stress•An efficient technique is used to condense out the strain variables in the mixed shell•The accuracy of the continuous and discrete rotation approaches is explored•An efficient scheme for updating the current director and its derivatives is proposed