These commands allow computation of three different types of responses:
- Displacement (label = DISP)
Displacement response refers to displacements, stresses, forces, etc.
Velocity response refers to velocities, stress velocities, force velocities, etc.
- Acceleration (label = ACEL)
Acceleration response refers to accelerations, stress accelerations, force accelerations, etc.
These commands can also be used to specify the type of modal forces used in the combination.For-
ceType=STATIC (default) combines the modal static forces (i.e., stiffness multiplied by mode shape
forces, both of which are stress-causing forces).ForceType=TOTAL combines the summed modal
static forces and inertia forces (i.e., stiffness and mass forces, both of which forces are seen by the
supports).
The DSUM method also allows the input of time duration for earthquake or shock spectrum.
The mode combination phase writes a file of POST1 commands (Jobname.MCOM). Read in Job-
name.MCOM in POST1 to do the mode combinations using the results file (Jobname.RST) from
the modal expansion pass.
The file Jobname.MCOM contains POST1 commands that combine the maximum modal responses
by using the specified mode combination method to calculate the overall response of the structure.
The mode combination method determines how the structure's modal responses are to be combined:
- If displacement is selected as the response type (label = DISP), displacements and stresses are combined
for each mode on the mode combination command.
- If velocity is selected as the response type (label = VELO), velocities and stress velocities are combined
for each mode on the mode combination command.
- If acceleration is selected as the response type (label = ACEL), accelerations and stress accelerations
are combined for each mode on the mode combination command.
Note
A DDAM spectrum analysis may alternately be performed in two separat e solves: first,
the spectrum solution, and then the mode combination. The damping needed by the
mode combination must be specified before the spectrum solve.
- Start solution.
Command(s):SOLVE
GUI: Main Menu> Solution> Solve> Current LS
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information
DDAM Spectrum Analysis Process
