Buckling constraints in the wing box optimization problem

[Gittwell]

Dears colleagues!

Please tell me, how I can set up optimization with a buckling constraints. I use tacs 3.3.1 and mphys 1.1.0.
I can add KSFailure constraint,but I can't find any information on how to add buckling constraints.

model.add_constraint("tip_shear.ks_vmfailure", lower=0.0, upper=1.0, scaler=1.0)

[Gittwell]

If it is useful to someone: smdogroup/tacs#347