Filter
Top Products
Section 5
5-357
5.37.1.6 Harmonic Ground Motion Loading
This set of commands may be used to specify harmonic ground
motion loading on the structure, the modal damping, and the phase
relationship of ground motions in each of the global directions.
Response at all of the frequencies defined in section 5.37.1.2 will be
calculated.
General format:
⎧ DAMP f ⎫ ⎧ ABS
2
⎫
HAR
MONIC GROUND
⎨ CDAMP ⎬ ⎨ ⎬
⎩ MDAMP ⎭ ⎩ REL ⎭
This command specifies the damping. The steady state response will
be calculated for each specified output frequency entered or
generated, see section 5.37.1.2.
DAMP , MDAMP and CDAMP. Select source of damping input.
f
2
= Damping ratio for all modes. Default value is 0.05 (5%
damping if 0 or blank entered).
DAMP indicates to use the f
2
value for all modes.
MDAMP indicates to use the damping entered or computed with
the DEFINE DAMP command if entered, otherwise default value
of 0.05 will be used.
CDAMP indicates to use the composite damping of the structure
calculated for each mode. One must specify damping for different
materials under the CONSTANT specification.
ABSolute or RELative. Ground motion results in output file will
be relative to the ground unless ABSolute is specified. Graphical
results are relative. This option has no effect for the force loading
cases.