1. But

In the context of multi-fiber modeling, there are two « levels » of modeling:

• the so-called « longitudinal » modeling represented by a beam (with geometric support SEG2)

• the plane modeling of the section (perpendicular to SEG2).

The operator DEFI_GEOM_FIBRE makes it possible to define the geometry of the groups of fibers that will be used in the definition of the cross section using the AFFE_CARA_ELEM operator.

The fibers can be described either using a plane mesh previously read by the operator LIRE_MAILLAGE (keyword SECTION) and/or in the form of « point » surfaces (keyword FIBRE or ASSEMBLAGE_FIBRE).

Each occurrence of SECTION, FIBRE, or ASSEMBLAGE_FIBRE defines a set of fibers that must be uniquely named. A set of fibers will have the same behavior for all of its fibers, defined using DEFI_COMPOR.

The command creates a geom_fibre data structure.

Attention:

With the information given in SECTION or FIBRE, it is possible to calculate the majority of the integrated characteristics of straight sections (area, static and quadratic moments). However, it is not possible to calculate the torsional inertias, warping and the position of the center of torsion. These quantities must be given to operator AFFE_CARA_ELEM.

If the fibers are defined based on a mesh, the operator MACR_CARA_POUTRE makes it possible to read this mesh and to calculate all the characteristics. The result of this operator is a table that can be an input to the AFFE_CARA_ELEM operator.