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PhilippB

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About PhilippB

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  1. Thank you Mr. Rajan. This was exactly what i was looking for. Best regards, Philipp
  2. Hello Everyone, I want to perform sensitivity analysis with size optimization for truss structures in OptiStruct. I need the sensitivities for the objective (min(MASS)) and for all of the stress constraints of the beam elements. Furthermore, I don’t want OptiStruct to do any optimization iteration and just need the sensitivities, so I perform a zero iteration optimization run (DOPTPRM,DESMAX,0) according to the description in OS-manual (“Sensitivity Analysis”, figure 8). I use OUTPUT,ASCSENS,ALL,STRESS to write a ASCII-file (“_.asens”) with the sensitivities. I did this procedure for a simple truss example, which I have attached to this post. My specific example has 10 design variables (radius of each of the 10 beams) and a stress constraint for each beam. So the sensitivity analysis should have to calculate 10 sensitivities for each of the 21 responses. There are 21 responses because there is a stress response for each end of a beam and one response for the objective. The problem I have, is that OptiStruct does not output the sensitivities of all responses. The number of sensitivities OptiStruct outputs depends on the current values of the design variables (in my case the starting values). So if I use really good starting values for example, OptiStruct outputs nearly all of the sensitivities. The concerned responses for which the sensitivities are missing aren't written in the RETAINED RESPONSE TABLE in the out-file, too. I tried to use RESPRINT and DREPORT options to output the responses manually, but this does not affect the calculation of the sensitivities. Do you have an idea how to get all of the sensitivities? Best regards, Philipp truss_example.fem
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