1. Introduction

Shell and plate elements are particularly used to model thin structures where the relationships between dimensions (thickness/characteristic length) are at most \(1/10\). They are therefore particularly involved in fields such as civil engineering, core REP internals, vibration analysis, Euler buckling analysis, the analysis of thin structures in elastic multi-layer composite material… We limit ourselves to the framework of small trips (even if it is possible but not recommended to use the update “PETIT_REAC”) and small deformations.

Unlike shell elements, flat plate elements do not make it possible to take into account the geometric curvature of the structure to be represented and induce parasitic flexures. It is therefore necessary to use a large number of these elements in order to correctly approach the geometry of the structure, especially since it is curved. On the other hand, we gain in simplicity of formulation and the number of degrees of freedom is reduced. Moreover, the formulations « Discrete Shear » (DST, DSQ and Q4g) or « Discrete Kirchhoff » (DKT, DKTG and DKQ, DKQG) of kinematics, with or without transverse distortion respectively, allow good results in terms of displacement and modal analysis respectively.

The support cells for these finite elements are linear (triangles and quadrangles). The degrees of freedom of these finite elements are the translations and the rotations of the vertex nodes. The characteristics that are assigned to them are: thickness, shear coefficient, eccentricity,…

How these elements are implemented in*code_aster* as well as some aspects of their use are given in the [§5] of this documentation.

In particular, these formulations are classified: