*** ERROR # 557 *** DRESP1 2 is not referenced above the first SUBCASE.

Heiko_H_870106

Hello Community,

I am struggling with ERROR # 557 in a topology optimization problem while trying to set up a weighted objective function.

My objective is to minimize a weighted combination of two responses: total volume and a specific displacement.

My Setup:

1. I have defined two DRESP1 responses:
   • DRESP1 (ID 1) for Displacement (from a static load subcase).
   • DRESP1 (ID 2) for Volume.
2. I am combining these two responses using a DRESP2 card,

DRESP2 3 kombi_an 1

+ DRESP1L 2 1 1 1

3. My objective function (DESOBJ) then references this DRESP2 response.

When I run the analysis, it stops with the following error

 *** ERROR # 557 *** DRESP1 2 is not referenced above the first SUBCASE. 

This type of response must be specified above the first  SUBCASE. 

This error occurs in DESOBJ 3.

I have already gone through many posts but couldn't solve the issue. The volume response is not subcase-dependent, but I don't know how to communicate this to OptiStruct.

Any support would be greatly appreciated.

Thanks and Regards,

Heiko

simply_support_DEQATN.fem

simply_support_DEQATN.out

Alberto Campagna

Hi,

sorry, but your setup does not have any sense. You cannot minimize a global and local response together. What you should do is setting the volume dresp1 as objective and the displacement as a constraint for example. In this way you have a constrained optimization instead of an unconstrained one.

You can try with something like this.

simply_support_DEQATN_1.fem

Hope this helps.

Kind Regards.

Alberto