Reissner-Mindlin shell implementation and energy conserving isogeometric multi-patch coupling

A shear-flexible isogeometric Reissner-Mindlin shell formulation using non-uniform rational B-splines basis functions is introduced, which is used for the demonstration of a coupling approach for multiple non-conforming patches. The six degrees of freedom formulation uses the exact surface normal vectors and curvature. The shell formulation is implemented in an isogeometric analysis framework for computation of structures composed of multiple geometric entities. To enable local model refinement as well as non-matching domains coupling, a conservative multi-patch approach using Lagrange multipliers for structured non-uniform rational B-splines patches is presented. Here, an additional border frame mesh is used to couple geometries during structural analyses. This frame interface approach avoids the problem of excessive constraints when multiple patches are coupled at one point. First, the shell formulation is verified with several reference cases. Then the influence of the frame interface discretization and frame penalty stiffness on the smoothness of the results is investigated. The effects of the perturbed Lagrangian method in combination with the frame interface approach is shown. In addition, results of models with T-joint interface connections and perpendicular stiffener patches are presented. Copyright (C) 2016 John Wiley & Sons, Ltd.