MODESELECT

Subcase Information Entry The MODESELECT command can be used in the I/O Options or the Subcase Information section to select a subset of computed modes in modal dynamic analysis subcases.

Format

MODESELECT (type) = n

Mode selection based on arbitrary mode numbers.

Alternate Format 1

MODESELECT (type, LMODES = lm)

Mode selection based on lowest modes.

Alternate Format 2

MODESELECT (type, LMODENM = lom, HMODENM = him)

Mode selection based on a range of mode numbers.

Alternate Format 3

MODESELECT (type, LFREQ = lof, HFREQ = hif, UNCONSET = m)

Mode selection based on a range of frequencies.

Definitions

Argument Options Description
type <STRUCTURE, FLUID>
STRUCTURE (Default)
The MODESELECT command references modes associated with structural analysis only.
FLUID
The MODESELECT command references modes associated with fluid analysis only.
n n > 0, n < 0

(Integer)
n > 0
Set identification number n of a set of mode numbers. The modes corresponding to the mode numbers specified in set n will be included in the analysis. If no such set exists, then mode n will be included in the analysis.
n < 0
Set identification number |n| of a set of mode numbers. The modes corresponding to the mode numbers specified in set |n| will be excluded from the analysis. If no such set exists, then mode |n| will be excluded from the analysis.
LMODES lm

(Integer > 0)

 Specifies the number of lowest modes to be selected.
LMODENM lom

(Integer > 0)

 Specifies the lower bound of the mode number range for selecting modes. 3
HMODENM him

(Integer > lom > 0)

 Specifies the upper bound of the mode number range for selecting modes. 3
LFREQ lof

(Real ≥ 0.0)

 Specifies the lower bound of the frequency range for selecting modes. 4
HFREQ hif

(Real > lof ≥ 0.0)

 Specifies the upper bound of the frequency range for selecting modes. 4
UNCONSET UNCONSET This flag indicates that the following fields specify a single mode or a set of modes for unconditional inclusion or exclusion.

When UNCONSET is used, the bounds of the frequency range (LFREQ and HFREQ) must be specified for the selected modes.
m m > 0, m < 0

(Integer)
m > 0
Set identification number m of a set of mode numbers. The modes corresponding to the mode numbers specified in set m will be unconditionally included in the analysis. If no such set exists, then mode m will be unconditionally included in the analysis.
m < 0
Set identification number |m| of a set of mode numbers. The modes corresponding to the mode numbers specified in set |m| will be unconditionally excluded from the analysis. If no such set exists, then mode |m| will be unconditionally excluded from the analysis.

Comments

  1. The MODESELECT I/O Options Entry is only supported in modal frequency response, modal transient and complex eigenvalue analyses. It is not supported in Response Spectrum Analysis.
  2. Multiple MODESELECT entries are allowed in a model. MODESELECT entries can be specified above the first subcase or within each subcase.
  3. If LMODENM is specified without HMODENM, a default value of 10000000 (ten million) is assumed for HMODENM. If HMODENM is specified without LMODENM, a default value of 1 is assumed for LMODENM.
    Defaults LMODENM HMODENM
    specified 1.0E+7
    1 specified
  4. If LFREQ is specified without HFREQ, a default value of 1.0E+30 is assumed for HFREQ. If HFREQ is specified without LFREQ, a default value of 0.0 is assumed for LFREQ.
    Defaults LFREQ HFREQ
    specified 1.0E+30
    0.0 specified
  5. When the MODESELECT Case Control command is used in conjunction with the parameter LFREQ, the MODESELECT Case Control takes precedence.
  6. If the use of MODESELECT results in all or none of the computed modes for use, you are informed with a message.
  7. The faster method for modal frequency response analysis (activated by PARAM,FASTFR,YES) cannot be used in conjunction with MODESELECT.
  8. Modes that are eliminated by MODESELECT will display an "S" next to the mode number, if the mode is eliminated by MODESELECT in one subcase and PARAM, LFREQ or PARAM, HFREQ in another subcase, or an "M" next to the mode number, if eliminated by MODESELECT in at least one subcase.