A flexible approach for coupling NURBS patches in rotationless isogeometric analysis of Kirchhoff-Love shells

This paper presents a flexible method for coupling NURBS patches in isogeometric Kirchhoff-Love shell analysis. The required C1-continuity in such a shell formulation significantly complicates the patch coupling (as compared to typical C0-cases). In the present work, the C0-part of the coupling is a global coupling in a weak sense, whereas the C1-continuity is enforced by a strong point-wise coupling in well-chosen collocation points along the interface. The coupling conditions can be derived using only mesh information, without the need for suitable penalty or stabilisation parameters. They are expressed using a master-slave formulation between the interface variables. A static condensation approach to enforce these continuity constraints results in a reduced system matrix. The proposed method can be employed for both conforming and non-conforming patch configurations, and for G1-continuous structures as well as for patches meeting at a kink. This is demonstrated for a set of problems of (dynamic) shell analysis, including both eigenvalue and boundary-value problems.