SED
SED, SEDX
, SEDY
, SEDZ
, Cname
Defines the excitation direction for response spectrum
and PSD analyses.
SEDX
,SEDY
,SEDZ
Global Cartesian coordinates of a point that defines a line (through the origin) corresponding to the excitation direction. For example: 0.0, 1.0, 0.0 defines global Y as the spectrum direction.
Cname
The component name corresponding to the group of excited nodes. Only applies to base excitation multi-point response spectrum analysis (SPOPT, MPRS) and power spectral density analysis (SPOPT, PSD). Defaults to no component.
Notes
In single-point response spectrum analysis (SPOPT,SPRS), the excitation
direction without rocking (ROCK) is normalized to one so that the
SEDX
, SEDY
, and
SEDZ
values do not scale the spectrum. The excitation direction with
rocking is not normalized. The SEDX
, SEDY
,
and SEDZ
values must be consistent with the linear components of
OMX
, OMY
, and
OMZ
values on the ROCK command. The calculated
direction then scales the spectrum. For more information, see Participation Factors and Mode Coefficients.
In multi-point response spectrum analysis
(SPOPT,MPRS) and power spectral density analysis
(SPOPT,PSD), the excitation direction is normalized
to one so that the SEDX
, SEDY
, and SEDZ
values do not scale the spectrum.
The component name (Cname
) is required.
The constraints corresponding to the excitation direction are applied
to the component nodes.
This command is also valid in PREP7.