DOBJREF – Design Objective for Minmax Problems
Defines a response and its reference values for a minmax (maxmin) optimization problem.
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DOBJREF |
DOID |
RID |
SID |
NEGREF |
POSREF |
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DOBJREF |
22 |
3 |
ALL |
-1.0 |
1.0 |
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DOBJREF |
22 |
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ALL |
-1.0 |
1.0 |
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DRESP1 |
3 |
TORN |
DISP |
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3 |
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488 |
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DRESP1 |
5 |
BUTTOM |
DISP |
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3 |
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601 |
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DOBJREF |
23 |
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ALL |
-1.0 |
1.0 |
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DRESP1 |
14 |
MISES |
STRESS |
PSHELL |
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DOID |
Design objective identification number. (integer > 0) |
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RID |
DRESP1 or DRESP2 identification number. (integer > 0) |
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SID |
Subcase identification number, use ALL if it applies to all subcases. Default = ALL (integer > 0, blank or ALL) |
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NEGREF |
Reference value for a negative response. Default = -1.0 (real or blank) |
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POSREF |
Reference value for a positive response. Default = 1.0 (real or blank) |
The same DOID can be used for multiple DOBJREF entries. If only one DOID is used, only one MINMAX=DOID entry is needed in the subcase information section.
The use of reference values allows users to set up general minmax problems involving different responses with different magnitudes. For these problems, the objective can be defined as:
where 
are response values,
and 
are corresponding reference values, which can take
different values depending on whether the response is positive or negative.
Typically, the target value or constraint value of a response can be used as its reference value. So, instead of the traditional optimization problem where there is a single objective and multiple constraints, the problem may be formulated as a minmax (maxmin) optimization, where all the responses which were previously constrained are defined as objectives and their bounds are used as reference values. This works toward pushing the maximum ratio of response versus bound value as low as possible, thus increasing the safety of the structure.
Go To
Guidelines for Bulk Data Entries
Alphabetical List of Bulk Data Entries