As an example, suppose the results file contains results for several load steps, and you want to compare
load steps 5 and 7 and store the maximum in memory. The commands to do this would look like this:
LCDEF,1,5! Load case 1 points to load step 5
LCDEF,2,7! Load case 2 points to load step 7
LCASE,1! Reads load case 1 into memory
LCOPER,MAX,2! Compares database with load case 2 and stores the
! maximum in memoryThe database now contains the maximum of the two load cases, and you can perform any desired
postprocessing function.
NoteLoad case operations (LCOPER) are performed only on the raw solution results in the solution
coordinate system.The solution results are:
- Element component stresses, strains, and nodal forces in the element coordinate systems
- Nodal degree-of-freedom values, applied forces, and reaction forces in the nodal coordinate systems
To have a load case operation act on the principal/equivalent stresses instead of the component stresses,
issue the SUMTYPE,PRIN command.
It is important that you know how load case operations are performed. Many load case operations, such
as mode combinations, involve squaring, which renders the solution results unsuitable for transformation
to the results coordinate system, typically the Global Cartesian, and unsuitable for performing nodal or
element averages. A typical postprocessing function such as printing or displaying average nodal stresses
(PRNSOL,PLNSOL), for example, involves both a coordinate system transformation to the results co-
ordinate system and a nodal average. Furthermore, unless SUMTYPE,PRIN has been requested, princip-
al/equivalent stresses are not meaningful when computed from squared component values.
To view correct mid-surface results for shells (SHELL,MID), use KEYOPT (8) = 2 (for SHELL181,SHELL208,
SHELL209,SHELL281, or ELBOW290). These KEYOPT settings write the mid-surface results directly to
the results file, and allow the mid-surface results to be directly operated on during squaring operations,
instead of averaging the squared TOP and BOTTOM results.
You should therefore use only untransformed (RSYS,SOLU), unaveraged (PRESOL,PLESOL) results
whenever you perform a squaring operation, such as in a spectrum (SPRS,PSD) analysis.
Use the FORCE command prior to any load case operations to insure that the forces are correctly
summed before the operation. Note that once a force type has been combined, the other components
are no longer available and will be zero.
7.3.3.1. Saving a Combined Load Case
By default, the results of a load case combination are stored in memory, overwriting the results portion
of the database. To save these results - for later review or for subsequent combinations with other load
cases - use one of the following methods:
- writing the data to a load case file
- appending the data to the results file.
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationThe General Postprocessor (POST1)