4. Operands#

4.1. Keyword BASE_MODALE#

♦ BASE_MODALE = _F (

Key word factor for defining the parameters for selecting the modal calculation base.

4.1.1. Operand MODE_MECA#

modemec is the mode_meca type concept containing dynamic modes.

4.1.2. Operands NUME_ORDRE/AMOR_REDUIT#

/NUME_ORDRE = the order

The order is the list of the order numbers of the modes of the modemec concept actually taken into account in the calculation. Example: \((\mathrm{2,}\mathrm{3,}4)\).

Lamor is the list of reduced modal depreciations corresponding to the modes selected. The number of items in the list is equal to the number of items in the order. Example: \((0.05,0.05,0.02)\). This keyword can only be used with NUME_ORDRE.

4.1.3. Operands BANDE/AMOR_UNIF#

/BANDE = (f1 f2)

The dynamic modes taken into account will be those of modemec whose frequency is in the band (f1 f2)

For each mode selected, the amortization is equal to amor. This keyword can only be used with BANDE.

4.2. Operand MODE_STAT#

◊ MODE_STAT = mosta

Mode_meca concept containing the static modes necessary for the calculation.

This keyword is only necessary in the case of a multi-support seismic calculation where the excitation is based on degrees of freedom (i.e. when the keyword GRANDEUR under the keyword factor EXCIT is equal to “DEPL_R”).

4.3. Keyword EXCIT#

♦ EXCIT = _F (

Keyword factor defining all parameters concerning arousal.

The keywords DERIVATION, GRANDEUR, and MODAL define the type of arousal.

The keywords INTE_SPEC, NUME_VITE_FLUI, NUME_ORDRE_I, NUME_ORDRE_J,, NOEUD_I,,, NOEUD_J, NOM_CMP_I, and NOM_CMP_J define the arousal interspectrum.

4.3.1. Operand DERIVATION#

When the magnitude of the excitation is of the imposed ddl type (“DEPL_R”), this keyword makes it possible to describe whether the excitation interspectrum should be considered as an imposed displacement, speed or acceleration. The user then specifies 0, 1, or 2.

This keyword is optional. By default, it is 0.

Note:

In the case of a seismic calculation, the excitation is often an acceleration. This keyword must then be equal to 2.

4.3.2. Operand GRANDEUR#

This keyword makes it possible to say whether the excitation is of the type forced ddl (“DEPL_R”), imposed force (“EFFO”), source of volume flow (“SOUR_DEBI_VOLU”), source of mass flow (“SOUR_DEBI_MASS”), source of pressure (“”), source of pressure (“SOUR_PRESS”), or source of fluid force (“SOUR_FORCE”).

This keyword is optional. By default, it is equal to “DEPL_R” and the excitation is of the type ddl of imposed displacement in all cases except in the case of supports represented by assembled vectors (keyword CHAM_NO).

4.3.3. Operands INTE_SPEC and NUME_VITE_FLUI#

These keywords define the interspectrum (s) of arousal.

interexc is the concept of an interspectrum type containing all the interspectral matrices (spectral density matrices) of excitation. It is taken into account as defined in the function associated with the concept, that is to say in particular that a possible spectrum folding is not interpreted.

For a function defined by:

\(f\in [{f}_{\mathrm{1,}}{f}_{2}]:\tilde{S}(f)\) given

We will interpret:

\(\begin{array}{}f<{f}_{1}:S(f)=0\\ f\in \left[{f}_{1},{f}_{2}\right]:S(f)=\tilde{S}(f)\text{donné}\\ f>{f}_{2}:S(f)=0\end{array}\)

If frequency loop \([{f}_{\mathrm{1,}}{f}_{2}]\) is to be reproduced for negative frequencies, you must:

  • or give the whole spectrum on the real axis,

  • or apply a coefficient 2 to the value of DSP, a workaround possible, since the spectral densities are assumed to be symmetric in the calculations performed by the DYNA_ALEA_MODAL command.

    The required parameters of the table are:

  1. if we index the parameters of the table by order numbers: “NUME_ORDRE_I” [I], “NUME_ORDRE_J” [I], “FONCTION” [K24]

  2. if not: “NOE UD_I “[K8], “NOE UD_J” [K8], “NOM_CMP_I” [K8], “NOM_CMP_J” [K8], “FONCTION” [K24].

  3. The table must be complete: presence of autospectra (diagonal term of the matrix) and interspectra (extra-diagonal term of the matrix).

This table can be generated by operators: DEFI_SPEC_MODAL, LIRE_INTE_SPEC, or CALC_INTE_SPEC. The reader is invited to consult the documentation for the TEST_FONCTION [:external:ref:`U4.92.02 <U4.92.02>`] command for more information on the meaning of the parameters.

◊ NUME_VITE_FLUI = nk

nk is the fluid speed serial number associated with interexc.

4.3.4. Operands NUME_ORDRE_I, NOEUD, NOM_CMP, CHAM_NO, and MODAL#

These keywords link the terms (row numbers in the matrix) of the excitation interspectrum and the excitation point (s) for modal excitation or when the parameters in the table have been indexed by order numbers.

♦/♦ NUME_ORDRE_I = (no1, no2,..)

This list of order numbers makes it possible to determine the term (line number) of the given interspectral matrix. The length of this list should correspond to the number of excitations imposed on the structure.

♦/♦ NOEUD = list_now

This keyword allows you to specify the nodes where multi-spectral excitation will be applied. Example (“N1”, “N5”, “N7”).

For all types of excitation quantities, except for pressure sources and force sources, list_noe contains as many terms as there are indices defining excitation interspectra.

In the case of pressure sources or force sources, each source is associated with a dipole, that is to say two points of application. list_noe then has twice as many terms as there are indices defining interspectra.

♦ NOM_CMP = list_cmp

This keyword makes it possible to specify the components on which multispectral excitation will be applied. Example (“PRES” “DRZ” “” PHI “).

These components must of course correspond to the degrees of freedom of the support nodes.

In all cases, list_cmp has the same number of items as list_noe.

For fluid sources, it is the degree of freedom “PRES” that is excited.

◊ MODAL = 'NON' [DEFAUT]

The arousal is not modal in this case.

/♦ cham_no= list_vass

When this keyword is present, each excitation press is an assembled vector defined previously in the command file. list_vass contains the list of assembled vectors that act as supports. The associated excitatory quantity is” EFFO “. It is recommended that the intensity associated with the effort that is imposed by this means be given by the interspectrum: the assembled vector essentially serves to define a form function supporting a spectrum of power under effort. So it is standardized.

This option makes it possible to assign a force power spectrum to a form function.

In all cases, list_vass contains as many terms as there are hints defining interspectra.

/♦ MODAL = “OUI”

The presence of “OUI” under this keyword implies that the arousal interspectrum is considered to be modal arousal.

4.3.5. Operands NOEUD_I and NOM_CMP_I#

These keywords link the terms (row numbers in the matrix) from the excitation interspectrum (s) and the excitation points when the parameters in the table have been indexed by physical data consisting of the pair (Node-Component).

♦/♦ NOEUD_I = ndi1, ndi2,...

♦ NOM_CMP_I = cmpi1, cmpi2,…

These lists are paired two by two in order to determine the term (line number) of the given interspectral matrix. The length of the preceding lists must correspond to the number of excitations imposed on the structure.

♦ NOM_CMP = list_comp [l_cmp]

These two keywords have the same meaning as in [§4.3.4].

◊ MODAL = 'NON' [DEFAUT]

                 The arousal is not modal in this case.

4.4. Keyword REPONSE#

♦ REPONSE = _F (

Factor keyword for the definition of all parameters concerning the response.

The following three keywords describe the type of response.

4.4.1. Operand DERIVATION#

◊ DERIVATION =

     This keyword has the same meaning as for the factor keyword EXCIT [:ref:`§4.3.1 <§4.3.1>`].

4.4.2. Operand OPTION#

If this keyword is specified with “DIAG”, then all non-diagonal functions in the response interspectrum are initialized to zero without being calculated. Only autospectra are calculated. If not (“TOUT”), all the functions of the response interspectrum are calculated.

4.4.3. Operands FREQ_MIN/FREQ_MAX/PAS/FREQ_EXCIT/NB_POIN_MODE#

These keywords are used to describe the frequency discretization in which the answer will be given.

♦ FREQ_MAX = fmax

fmin and fmax are the two limits of the frequency range. step is the minimum discretization step.

If the values of fmin and fmax are given, then by default no is \(\frac{{f}_{\mathrm{max}}-{f}_{\mathrm{min}}}{100}\) by default.

Otherwise, fmax is taken as the greatest natural frequency of the dynamic modes selected for the calculation.

So discretization covers domain \([0;{\mathrm{2.f}}_{\mathrm{max}}]\), \(\mathrm{pas}=\frac{{\mathrm{2.f}}_{\mathrm{max}}}{100}\).

On the other hand, if not is present, we ensure that the discretization step of the response is everywhere less than the step.

/”SANS”

If the user gives the argument “AVEC” under the FREQ_EXCIT keyword, then the excitation frequencies are integrated into the discretization of the response (option by default). If he gives the argument “SANS”, they will be ignored. This keyword is set to “SANS” if the FREQ_MIN keyword is present.

The response is more refined at the natural frequencies in order to ensure a good description of the response at the peak location.

The keyword NB_POIN_MODE allows you to define the number of frequency steps per natural frequency taken into account. By default, there are 50 steps per natural frequency. This keyword is not taken into account if FREQ_MIN is given.

By default, each function of the interspectrum will have a “linear” interpolation mode and an extension mode outside the discretization domain of type “EXCLU”.

4.5. Operand TITRE#

◊ TITRE = title

title is the title of the calculation. It will be printed at the top of the results. See [U4.03.01].

4.6. Operand INFO#

◊ INFO =

Specify the print options on file MESSAGE.

1

no printing

2

recalls the calculation options selected.