I stumbled upon similar problem.
I have a simple truss, where chords should be 0.9 utilization, braces 0.7
For tension, Clemens’ method would work, since material yield strength is proportional to resistance.
For compression though it doesn’t work, buckling is way more important and reduction of yield strength doesn’t correlate linearly.
What I did was create two separate models, one with CroSec Optimization using utilization of 0.7, other using 0.9.
Then made a final third model using AnalyzeThII with fixed cross sections taken from previous two models, chords from 0.9, braces from 0.7.
Problem is that because of different stiffness’s, forces are allocated differently, and because of that final utilization is different.
Chord utilization usually goes a little bit above 0.9.
But so far, it has been acceptable.
@karamba3d, could it be possible to introduce such functionality in the future? Some of my colleagues would be very glad.
The other thing would be using CroSec optimization, deflection check only for particular load combinations.
Currently I push ULS and SLS combinations into the same solver, because of that, I can’t use deflection check, since it would check deflection for ULS combinations…
Pushing them in different solvers would lead to different profiles.