3. Operands

3.1. Operand MATR_MASS

♦ MATR_MASS = m

Mass matrix \(M\) of the system, built with the boundary conditions for blocking the supports.

3.2. Operand DIRECTION

♦ DIRECTION = (d1, D2, D3, D3, R1, R2, R3)

Components of the vector giving the direction of the driving movement of the earthquake in the global coordinate system. It is a list of three reals if the accelerograms imposed are only for translations. If we also impose infinitesimal rotational accelerations, we expect a list of six real numbers (valid for models with discrete elements or finite elements of structures with degrees of freedom of rotation) .This vector :math:`\Delta` will be normalized automatically by the operator. For example, if we provide: DIRECTION = (1., 2., 2.,), the result will be the same as for: DIRECTION = (0.333, 0.666, 0.666, 0.666,).

3.3. Description of the training movement

3.3.1. Operand MONO_APPUI

♦/MONO_APPUI = 'OUI'

The structure is excited uniformly on all its supports: the driving movement is rigid, in the direction given by the keyword DIRECTION (in general translation, but we can also consider an infinitesimal rotation).

In accordance with what is explained in the reference document [R4.05.01] the CALC_CHAR_SEISME operator calculates the following expression:

\(-M\mathrm{.}\Delta\)

with \(\Delta\) the direction of the earthquake specified by the DIRECTION operand.

3.3.2. Multi-support excitation

In this case, the accelerations undergone by all the support points of the structure under study are not necessarily identical or in phase. The training movements are not rigid bodies, but are described by linear elastic static modes.

3.3.2.1. Operand MODE_STAT

/MODE_STAT = fashion

Static modes of the structure: mode_meca concept produced by the operator MODE_STATIQUE [U4.52.14] with the option MODE_STAT. They correspond to the \(6\times {\mathrm{nb}}_{\mathrm{appuis}}\) linear elastic static modes with a unitary degree of freedom imposed on the supports where \({\mathrm{nb}}_{\mathrm{appuis}}\) is the number of different accelerograms (translations, rotations) undergone by the structure and defined on each unitary degree of freedom imposed on each support in question.

Note:

If the structure is only required by translational degrees of freedom, then \(3{\mathrm{nb}}_{\mathrm{appuis}}\) static modes.

3.3.2.2. Operand GROUP_NO

List of groups of nodes (g_noeu) of the structure subjected to seismic excitation: these nodes support the degrees of freedom of support of the structure to which the imposed movements are applied.

In accordance with what is explained in the reference document [R4.05.01] the CALC_CHAR_SEISME operator calculates the following expression:

\(-M\mathrm{.}{\Psi }_{Pj}\mathrm{.}s\)

with \(s\) the direction of the earthquake, specified by operand DIRECTION, and \({\Psi }_{Pj}\) the unitary linear static modes, specified by operand MODE_STAT, calculated for each degree of freedom of the blocked supports listed in the node groups (g_noeu).

3.4. Operand TITRE

◊ TITRE = title

Title attached to the concept produced by this operator [U4.63.01].