Group Operations for Reaction Forces/Moments

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
END_

GROUP_OPER is default GROUP_OPER = MAX.
Other options of MAX and SUM are invalid.
A node group (ND_GROUP) must 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.

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:


$R_{31} \leq R^{}$ $R_{32} \leq R^{}$ $R_{33} \leq R^{*}$

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:


$R_{31} + R_{32} + R_{33} \leq R *$

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:


$R_{31} \leq R^{}$ $R_{32} \leq R^{}$ $R_{33} \leq R^{*}$

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.