11. Tags GEOM_FIBRE/MULTIFIBRE#

11.1. Syntax#

11.2. Purpose#

11.3. Keyword MULTIFIBRE#

11.4. Keyword GEOM_FIBRE#

11.5. Operands PREC_AIRE/PREC_INERTIE#

11.3.1. Operands GROUP_MA#

11.3.2. Operand GROUP_FIBRE#

GEOM_FIBRE = fiber [geom_fiber]

MULTIFIBRE = _F (

♦ GROUP_MA = lgrma, [l_gr_mesh]

♦ GROUP_FIBRE = gfbr, [l_gr_fiber]

◊ PREC_AIRE = accurate (0.01), [real (default)]

◊ PREC_INERTIE = accurate (0.10), [real (default)]

Key words used to define the section of multifibre beams, (models POU_D_EM or POU_D_TGM), (models or) by assigning to the beam element (mesh SEG2) groups of fibers defined using the DEFI_GEOM_FIBRE operator (U4-26.01).

In the context of multi-fiber modeling, there are two « levels » of modeling. There is the so-called « longitudinal » modeling which will be represented by a beam (with geometric support SEG2) and a plane modeling of the section (perpendicular to SEG2). The MULTIFIBRE keyword allows fiber groups (previously defined by the DEFI_GEOM_FIBRE operator) to be associated with a beam element. GEOM_FIBRE allows you to give the name of the concept created by DEFI_GEOM_FIBRE containing the description of all the fiber groups.

Note:

For the elements POU_D_EM , it is necessary to assign all the fiber groups defining the straight section to a single beam element (see R3.08.08). On the other hand, for the elements POU_D_TGM , you can currently only assign one fiber group per beam element. If we want to deal with cases of heterogeneous section with elements POU_D_TGM , the operator CREA_MAILLAGE allows the support SEG2 to be duplicated so that there is only one material per support.

Attention:

The information contained in the fiber groups makes it possible to calculate some of the integrated characteristics of straight sections (area, static and quadratic moments). Despite this, for the elements POU_D_TGM , it is necessary to give consistent values for the operands \(A,\mathrm{IY},\mathrm{IZ}\) under the keyword POUTRE. A check is carried out on the consistency of these quantities. If the relative error is too large (Confer keywords PREC_AIRE , PREC_INERTIE ) a fatal error is issued.

♦ MULTIFIBRE

Define the beam mesh entities concerned and the sections that are assigned to them.

♦ GROUP_MA

This operand allows you to define the entities of the beam mesh (elements SEG2) that are concerned by the occurrence of the factor keyword:

Operands	Content/Meaning
GROUP_MA	Assigning to a list of mesh groups

♦ GROUP_FIBRE

These operands make it possible to define the fiber groups (among all those defined in the fiber geometry concept given by the keyword GEOM_FIBRE) that are assigned to the beam elements of this occurrence of

♦ GEOM_FIBRE

Concept created by DEFI_GEOM_FIBRE [U4.26.01], containing the description of all fiber groups in the study.

When the section is defined by a mesh (key mesh_sect under the operand SECTION * of the command DEFI_GEOM_FIBRE * ) the calculation of the global inertia of all surface elements does not take into account the inertia specific to each of the elements. It is therefore necessary to define a sufficient number of fibers for this error to be low and to remain less than prec_inertia . For example a rectangular section cut uniformly in the height in \(n\) elements leads to the following errors, on the inertia values.

Inertia error

◊ PREC_AIRE = accurate (0.01), [real (default)]

◊ PREC_INERTIE = accurate (0.10), [real (default)]

The use of multifibre beams (POU_D_EM or POU_D_TGM) requires providing additional information, compared to the keywords VALE and CARA, under POUTRE.

The objective is to check the consistency of the information (AIRE and INERTIE) provided on the one hand by the keyword POUTRE and on the other hand by the keyword MULTIFIBRE. The error criterion is based on the relative error and is compared either to the value by default or to that given by the user via the keywords PREC_AIRE and PREC_INERTIE.

If the criterion is not met a fatal error is generated. The relative error is calculated as follows:

\(\frac{{\mathit{AIRE}}_{\mathit{POUTRE}}-({\mathit{AIRE}}_{\mathit{SECTION}}+{\mathit{AIRE}}_{\mathit{FIBRE}})}{{\mathit{AIRE}}_{\mathit{POUTRE}}}\le \text{PREC\_AIRE}\)

\(\frac{{\mathit{INERTIE}}_{\mathit{POUTRE}}-({\mathit{INERTIE}}_{\mathit{SECTION}}+{\mathit{INERTIE}}_{\mathit{FIBRE}})}{{\mathit{INERTIE}}_{\mathit{POUTRE}}}\le \text{PREC\_INERTIE}\)

Notes:

• AIRE (fiber), AIRE (sect ION), * (sect), INERTIE (sect ION), * INERTIE (fiber) are calculated from the data structure describing the fibers and defined under the keyword geom_fiber. This data structure is created by the command defi_geom_fibre [U4.26.01] .

• AIRE (fiber) is calculated by summing the fiber areas, for all fiber groups defined by the keyword group_fiber from the operand fiber from the command defi_geom_fiber command.

• AIRE (sect ION) is calculated by summing the fiber areas defined by the keyword group_fiber of the operand section of the command defi_geom_fiber.

• INERTIE (fiber) is calculated by summing the \({\mathit{s.d}}^{2}\) of the fibers defined in the set of fiber groups defined by the key group_fiber of the operand fiber of the command defi_geom_fiber.: represents the area of a fiber.: represents the area of a fiber and d the distance between the fiber and the axis defined by the key * fiber of the command defi_geom_fiber.: represents the area of a fiber and d the distance between the fiber and the axis defined by the key * fiber of the command defi_geom_fiber.: represents the area of a fiber and d the distance between the fiber and the axis defined by the key * fiber of the command defi_geom_fiber.: represents the area of a fiber the fiber operand of the defi_geom_fiber command.

INERTIE (sect ION) is calculated by summing the s.d² of the elements defined by the key GROUP_FIBRE of the operand SECTION of the command DEFI_GEOM_FIBRE.: represents the area of an element and d the distance between the center of gravity of the element and d the distance between the center of gravity of the element and the distance between the center of gravity of the element and the axis defined by the keyword CARA_AXE_POUTRE of the operand SECTION of the command DEFI_GEOM_FIBRE .

Notes: