StructuralJoe,
When I looked your second picture, I can tell without any doubt that the vertical green member will buckle without bracing. The blue one is a tension member at vertical loads therefore it can't buckle. I don't think the failure has anything to do with the lateral wind loads.
Assume the depth of each of your beam is H and length is L.
1. Find Mn of your composite beam section;
2. The total nominal shear capacity Pn required to be designed along half length of beam between two beam surface can be conservatively estimated as: Vn = Mn/H.
3. Assume you are going to use...
you may not able to "fix" your FEM until you can better explain the testing and FEM curves.
The width of positive pulse of the testing curve can approximately represent the contact time between plate and hat and the negative pulse width represents how "loss" or how "flexible" the rotational...
