About Group Operations for Design Responses

For extracting one scalar value from a field of analysis results for a number of group entities into one design response, it is necessary to combine these results using an operator (GROUP_OPER). 


DRESP
  ID_NAME        =
  DEF_TYPE       =
  TYPE           =
  UPDATE         =
  ND_GROUP       = <group_entities_for_combination>
  EL_GROUP       = <group_entities_for_combination>
  GROUP_OPER     = MAX | MIN | AVERAGE| SUM | COUNT
END_

The following group operators exist:

  • MAX: extracts the maximum value within the group
  • MIN: extracts the minimum value within the group
  • AVERAGE: extracts the average value within the group
  • SUM: sums up all values of the entities of the group
  • COUNT: counts the number of entities of the group (cannot be used for the design response, only applicable for variables)

For the different types of terms, default settings for the operator exist. For all displacement, forces, stresses, strains and other nodal values, the default operator is MAX.

For all element-related entities (except the stresses and strains), the default operator is SUM.

Important:
  1. It is recommended to specify the operator directly in order to make sure that the correct settings are used.
  2. Maximal 5000 design responses are allowed. Therefore, the maximal number of nodes for GROUP_OPER = MAX is restricted to 5000, as internally there is created one design response for each node.
  3. For sensitivity-based optimization, the objective function built from design responses combining several entities (nodes) will be replaced by a substitute expression built from the single design responses. For TARGET=MAX this means that the sum of the single design responses is optimized. For an example see Group Operations for Displacements.
  4. Not all group operators make sense for all kind of design responses. An overview which group operators are admitted for specific design responses can be found in Design Response Combination.