mmass#

SpectrumOptions.mmass(option='', zpa='', **kwargs)#

Specifies the missing mass response calculation.

Mechanical APDL Command: MMASS

Parameters:
optionstr

Flag to activate or deactivate missing mass response calculation.

  • 0 (OFF or NO) - Deactivate (default).

  • 1 (ON or YES) - Activate.

zpastr

Zero Period Acceleration Value. If a scale factor FACT is defined on the svtyp command, it is applied to this value.

Notes

The missing mass calculation is valid only for single point excitation response spectrum analysis ( spopt, SPRS) and for multiple point response spectrum analysis ( spopt, MPRS) performed with base excitation using acceleration response spectrum loading. Missing mass is supported in a spectrum analysis only when the preceding modal analysis is performed with the Block Lanczos, PCG Lanczos, Supernode, or Subspace eigensolver (Method =LANB, LANPCG, SNODE, or SUBSP on the modopt command).

The velocity solution is not available ( Label = VELO on the combination command: srss, cqc…) when the missing mass calculation is activated.

The missing mass calculation is not supported when the spectrum analysis is based on a linear perturbation modal analysis performed after a nonlinear base analysis.

The missing mass is not supported when superelements are present.

To take into account the contribution of the truncated modes, the residual vector ( resvec ) can be used in place of the missing mass response. This is of particular interest if the velocity solution is requested or if a nonlinear prestress is included in the analysis (linear perturbation), or if a superelement is present, since the missing mass cannot be used in these cases.

In a multiple point response spectrum analysis ( spopt,MPRS), the mmass command must precede the participation factor calculation command ( pfact ).

This command is also valid in PREP7.