3. Operands#
3.1. Operands UNITE_RESU_IMPE and UNITE_RESU_FORC#
♦ UNITE_RESU_IMPE =/simple, [I]
/32, [DEFAUT]
The logical unit of the interface impedance matrix file calculated by CALC_MISS option TYPE_RESU =” FICHIER “. This matrix can either already be calculated and given as an entry in the study profile, or the result of CALC_MISS in the same command file.
♦ UNITE_RESU_FORC =/uresfor, [I]
/33, [DEFAUT]
Logical unit of the file of seismic interface forces previously calculated by MISS3D with CALC_MISS in post-processing and data as input to the study profile.
3.2. Operand TYPE#
◊ TYPE =/'BINAIRE'
/”ASCII” [DEFAUT]
This operand makes it possible to read the impedances calculated by the CALC_MISS [U7.03.12] command in a binary format file if necessary.
3.3. Keyword factor EXCIT_SOL#
If you want to obtain a temporal response, you must give one or more accelerograms using the keywords ACCE_X, ACCE_Y and ACCE_Z.
Note:
If EXCIT_SOL is not entered, then DYNA_ISS_VARI outputs the spectral response densities (for unitary excitation) .
3.3.1. Operands ACCE_X, ACCE_Y, and ACCE_Z#
◊ ACCE_X = access [saster_function]
◊ ACCE_Y = access [saster_function]
◊ ACCE_Z = access [sdaster_function]
Accelerographs, respectively in the \(X\), \(Y\), and \(Z\) directions. If several operands are entered then the signals must have the same abscissa.
The frequency discretization is determined from the temporal discretization of the accelerograms:
\(\mathit{FREQ}\text{\_}\mathit{INIT}\mathrm{=}0.0,\mathit{PAS}\mathrm{=}1.\mathrm{/}(\mathit{NB}\mathrm{\ast }\mathit{DT})\),
where NB is the number of time steps in the accelerogram and DT is the time step.
Note:
The accelerogram time step must be constant.
3.4. Operands FREQ_MAX and FREQ_PAS#
If EXCIT_SOL is present, in order to reduce the calculation time, it is possible to indicate the frequency step and the maximum frequency for calculating the transfer function (recommended):
◊ FREQ_MAX = fmax
◊ FREQ_PAS = step
If FREQ_MAX and FREQ_PAS are entered, then the transfer function is determined, taking into account spatial variability, only for a reduced number of frequencies. To calculate the temporal response to the excitation by a seismic signal (accelerogram), these values are interpolated in order to arrive at the frequency discretization required by the Shannon theorem.
If FREQ_MAX is less than the cutoff frequency \((\mathrm{NB}-1)\ast \mathrm{PAS}\) of the signal, then the response is completed with zeros up to the cutoff frequency. The last frequency of the calculation is therefore the cutoff frequency.
It is important to check that step FREQ_PAS is not too small to properly model the transfer function with spatial variability.
3.5. Operand NB_FREQ#
If you want to calculate spectral densities, then you must indicate the discretization parameters in the following frequency domain (harmonic calculation):
♦ NB_FREQ = NF
Number of frequency steps to be calculated.
♦ FREQ_INIT = over
Frequency at which harmonic calculation starts.
♦ FREQ_PAS = not
Value of the frequency step for harmonic calculation.
◊ OPTION =/'TOUT', [DEFAUT]
/”DIAG”,
By default, the DSP matrix of the transfer function (or of the response for a unit excitation) is obtained at the output. If we choose OPTION =” DIAG “, then we only get the diagonal terms of this matrix.
Note:
This is DSP in generalized coordinates. In most studies, you must first do the projection with the complete DSP matrix to retain only the diagonal terms of the DSP response in physical coordinates.
3.6. Operand NOM_CMP#
♦ NOM_CMP =/'DX',
/”DY”, /”DZ”,
Name of the component corresponding to an incident seismic field direction. This keyword is to be entered only if NB_FREQ is present.
3.7. Operand ISSF#
◊ ISSF =/'OUI'
/”NON” [DEFAUT]
This operand indicates whether or not we have a fluid domain and therefore also fluid-structure and sol-fluid interfaces indicated by the operands GROUP_MA_FLU_STRet GROUP_MA_FLU_SOLdans the command IMPR_MACR_ELEM [U7.04.33].
3.8. Keyword INTERF#
3.8.1. Operand MODE_INTERF#
♦ MODE_INTERF =/'TOUT',
/”CORP_RIGI” /”QUELCONQUE”
This operand makes it possible to characterize the type of interface modes of the model. Three types of interface modes are possible: if we choose a model based on the six rigid body modes, we must enter “CORP_RIGI”, if we work with all the interface modes (finite element unit modes), we enter “TOUT”. For all the other foundation cases (pressed geometry, any representation modes for flexible foundations, case ISSF =” OUI “), enter” QUELCONQUE “.
3.8.2. Operand GROUP_NO_INTERF#
♦ GROUP_NO_INTERF = gr_inter
With this keyword, we define the group of nodes based on the surface meshes that make up the soil-structure interface.
3.9. Keyword MATR_COHE#
3.9.1. Operands VITE_ONDE and PARA_ALPHA#
♦ TYPE = model
We can choose between the Mita & Luco coherence function (MITA_LUCO) and three empirical coherence functions established by Abrahamson (ABRAHAMSON, ABRA_ROCHER, ABRA_SOLMOYEN).
If we choose MITA_LUCO, then we can enter:
♦ VITE_ONDE = :math:`{V}_{s}`
◊ PARA_ALPHA = :math:`\alpha`
These are the parameters of the Luco and Wong coherence function (pure incoherence without the effect of wave passage):
\(\gamma (d)=\text{exp}[-(\alpha \mathrm{.}2\pi f\mathrm{.}\frac{d}{{V}_{s}}{)}^{2}]\)
where*d* refers to the distance between two points i and j on the foundation, \(f\) is the frequency and \({V}_{s}\) the wave propagation speed. The propagation speed VITE_ONDE initially considered by Mita & Luco is equal to 600m/s. The parameter \(\alpha\) is dimensionless, by default it is taken equal to 0.1.
Abrahamson’s three models are
ABRAHAMSON: Abrahamson’s generic consistency model (EPRI 1014101, 2006)
ABRA_ROCHER: model for a rock site established by Abrahamson based on earthquakes recorded at Pinyon Flat, USA (EPRI 1015110, 2007).
ABRA_SOLMOYEN: model for an average soil site established by Abrahamson based on various average soil sites in USA (EPRI 1015110, 2007).
3.10. Keyword MATR_GENE#
3.10.1. Operands MATR_MASS, MATR_RIGI, MATR_AMOR#
♦ MATR_MASS = m
Name of the concept assembled matrix corresponding to the generalized mass matrix of the system.
♦ MATR_RIGI = rigigen
Name of the concept assembled matrix corresponding to the generalized stiffness matrix of the system.
Hysterical damping is achieved with a complex stiffness matrix.
◊ MATR_AMOR = amogen
Name of the concept generalized matrix assembled corresponding to the generalized damping matrix of the system.
3.11. Operand PRECISION#
◊ PRECISION = prec
By default, this parameter is taken equal to 0.999.
To calculate the seismic forces with spatial variability of the incident field, the spectral decomposition of the coherence matrix \([{\gamma }_{\mathrm{ij}}]\), \(i=\mathrm{1...},M\) is carried out. The parameter prec gives the portion of the « energy » of the matrix that is conserved by retaining only a reduced number of eigenvectors. If we designate by \(K\ll M\) the number of eigenvalues retained (we retain the \(K\) largest eigenvalues), we have
\(\text{prec}\mathrm{=}\frac{\mathrm{\sum }_{i\mathrm{=}1}^{K}{\lambda }_{i}^{2}}{\mathrm{\sum }_{i\mathrm{=}1}^{M}{\lambda }_{i}^{2}}\)
3.12. Operand INFO#
◊ INFO =
Indicates the level of printing of operator results.
1 = |
no particular impression, |
2 = |
impression of the eigenvalues of the spectral decomposition retained. |
The prints are done in the file “MESSAGE”.