# DOBJREF

Bulk Data Entry Defines a response and its reference values for a minmax (maxmin) optimization problem.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DOBJREF DOID RID SID NEGREF / LID POSREF / UID LOWFQ HIGHFQ

## Example 1

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DOBJREF 22 3 ALL -1.0 1.0
DOBJREF 22 5 ALL -1.0 1.0
Table 1. Associated Cards
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DRESP1 3 TOP DISP     3   488
DRESP1 5 BOTTOM DISP     3   601

## Example 2

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DOBJREF 23 14 ALL -1.0 1.0
Table 2. Associated Cards
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
DRESP1 3 TOP DISP     3   488
DRESP1 5 BOTTOM DISP     3   601

## Definitions

Field Contents SI Unit Example
DOID Design objective identification number.

(Integer > 0)

RID DRESP1 or DRESP2 identification number.

(Integer > 0)

SID Subcase identification number.
ALL (Default)
If it applies to all subcases
blank

(Integer > 0)

NEGREF/ LID
NEGREF
Default = -1 (Real < 0.0)
Reference value for a negative response (should always be a negative real number or blank). 2 3 5
LID
No default <Integer>
Table identification number of a TABLEDi entry that specifies the negative reference as a function of loading frequency. 2 3 5

POSREF/ UID
POSREF
Default = 1.0 (Real > 0.0)
Reference value for a positive response (should always be a positive real number or blank). 2 3 5
UID
No default <Integer>
Table identification number of a TABLEDi entry that specifies the positive reference as a function of loading frequency. 2 3 5

Default = 0.0 (Real ≥ 0.0)

Default = 1.0E+20 (Real ≥ LOWFQ)

1. 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.
2. 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:(1)
$\mathit{Minimize} \text{max} \left({W}_{1}\left(x\right)/{r}_{1}, {W}_{2}\left(\text{x}\right)/{\text{r}}_{2},\dots {W}_{k}\left(x\right)/{r}_{k}\right)$
Or, alternatively:(2)
$\mathit{Maximize} \text{max} \left({W}_{1}\left(x\right)/{r}_{1}, {W}_{2}\left(x\right)/{\text{r}}_{2},\dots {W}_{k}\left(x\right)/{r}_{k}\right)$
Where,
${W}_{k}$
Response values
${r}_{k}$
Are corresponding reference values, which can take different values depending on whether the response is positive or negative.
3. 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.
4. LOWFQ and HIGHFQ apply only to response types related to a frequency response subcase (DRESPi, RTYPE = FRDISP, FRVELO, FRACCL, FRSTRS, FRSTRN, FRFORC, FRPRES and FRERP). The reference values NEGREF and POSREF are applied only if the loading frequency falls between LOWFQ and HIGHFQ. If ATTB of DRESP1 specifies a frequency value, LOWFQ and HIGHFQ are ignored.
5. LID and UID identify a loading frequency dependent tabular input using TABLEDi. They are applied analogous to LOWFQ, HIGHFQ. 4
6. The recommended setup to define Minmax or Maxmin models which reference several responses is:
• Create multiple DOBJREF entries with the same DOID
• Each DOBJREF entry references one response
• MINMAX or MAXMIN entry should reference the single ID corresponding to all DOBJREF entries.
7. This card is represented as a design objective reference in HyperMesh.