Group Operations for Reaction Forces/Moments | ||
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The structure for defining a DRESP for reaction force(s) or reaction moment(s):
DRESP ID_NAME = ..... DEF_TYPE = SYSTEM TYPE = ..... GROUP_OPER = MAX or SUM ND_GROUP = .....or use the NODE-definition NODE = .....or use the ND_GROUP-definition LC_SEL = ..... END_
- GROUP_OPER is default GROUP_OPER = MAX.
- Other options of MAX and SUM are invalid.
- A node group (ND_GROUP) has to be applied in the DRESP when more than one node is required.
- Maximal 5000 DRESPs can be defined. Therefore, the maximal number of nodes for GROUP_OPER = MAX is 5000 or less as for each group member a design response is created.
- The maximal number of nodes for GROUP_OPER = SUM is unlimited.
- GROUP_OPER = SUM is not allowed for absolute values.
The picture below shows a structure where the reaction forces in the y-direction of the three nodes 31, 32, 33 should be applied in a set of constraints using GROUP_OPER=MAX or GROUP_OPER=SUM.
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For the use in CONSTRAINTs is, initially, a node group defined containing the nodes 31, 32 and 33 (see figure above) yielding
GROUP_DEF ID_NAME = reac_NODES TYPE = NODE FORMAT = LIST LIST_BEGIN 31, 32, 33 END_
GROUP_OPER = MAX
Based upon the node group a design response for the reaction force in y-directions are defined in a DRESP using GROUP_OPER=MAX yielding
DRESP ID_NAME = DRESP_REAC_MAX DEF_TYPE = SYSTEM TYPE = REACTION_FORCE_Y LC_SET = STATIC,1, ND_GROUP = REAC_NODES GROUP_OPER = MAX END_
Internally, SIMULIA Tosca Structure generates three DRESPs. One DRESP for the reaction force of node 31, one DRESP for the reaction force of node 32 and one DRESP for the reaction force of node 33.
If one then applies the DRESP in a constraint yielding:
CONSTRAINT ID_NAME = CONSTRAINT_MAX DRESP = DRESP_REAC_MAX MAGNITUDE = ABS LE_VALUE = <value> END_
SIMULIA Tosca Structure then generates three reaction force constraints like the following:
GROUP_OPER = SUM
Based upon the node group a design response for the reaction force in y-directions are defined in a DRESP using GROUP_OPER=SUM yielding
DRESP ID_NAME = DRESP_REAC_SUM DEF_TYPE = SYSTEM TYPE = REACTION_FORCE_Y LC_SET = STATIC,1, ND_GROUP = REAC_NODES GROUP_OPER = SUM END_
Internally, SIMULIA Tosca Structure generates one DRESP consisting of the sum of the reaction forces of the nodes 31, 32 and 33.
If one then applies the DRESP in a constraint yielding:
CONSTRAINT ID_NAME = CONSTRAINT_MAX DRESP = DRESP_REAC_MAX MAGNITUDE = ABS LE_VALUE = <value> END_
SIMULIA Tosca Structure then generates a single reaction force constraint like the following:
Alternative Definition of Constraints Function
Alternatively, one could also define three DRESPs for each node like the following:
DRESP ID_NAME = DRESP_REAC_1 DEF_TYPE = SYSTEM TYPE = REACTION_FORCE_Y NODE = 31 LC_SET = STATIC,1 GROUP_OPER = MAX or SUM END_ DRESP ID_NAME = DRESP_REAC_2 DEF_TYPE = SYSTEM TYPE = REACTION_FORCE_Y NODE = 32 LC_SET = STATIC,1 GROUP_OPER = MAX or SUM END_ DRESP ID_NAME = DRESP_REAC_3 DEF_TYPE = SYSTEM TYPE = REACTION_FORCE_Y NODE = 33 LC_SET = STATIC,1 GROUP_OPER = MAX or SUM END_
And then add the three design response in three constraints:
CONSTRAINT ID_NAME = CONSTRAINT_1 DRESP = DRESP_REAC_1 MAGNITUDE = ABS LE_VALUE = <value> END_ CONSTRAINT ID_NAME = CONSTRAINT_2 DRESP = DRESP_REAC_2 MAGNITUDE = ABS LE_VALUE = <value> END_ CONSTRAINT ID_NAME = CONSTRAINT_3 DRESP = DRESP_REAC_3 MAGNITUDE = ABS LE_VALUE = <value> END_
SIMULIA Tosca Structure then generates three reaction force constraints like the following:
Consequently, it can be concluded that there is fundamental difference in the constraints if a node group (ND_GROUP) consisting of more than one node is applied and the choice of GROUP_OPER.