Novel Curvilinear 2|3D Unified Finite Element Formulations for the Analysis of Complex Shell Structures

In this paper, a detailed locking analysis of novel curvilinear finite element models for the analysis of shells is proposed. In the introduced methodology, novel higher-order shell models are proposed in a non-orthogonal reference frame, recovering the classical Cartesian description via a consistent transformation law. The shell models are defined within the well-established Carrera Unified Formulation (CUF) framework, by which Lagrange-based theory of structures are merged with classical finite element interpolation of the reference mid-surface, obtaining novel shell elements with enhanced three-dimensional geometrical modeling capabilities. By exploiting the computational efficiency of 2D models, these novel 2|3D elements are now being adopted in locking investigations to assess the accuracy and capabilities of the proposed approach when complex structural problems are addressed. The methodology is validated by analyzing classical numerical benchmarks and patch tests proposed in the literature.