X Bracing for retrofitting

[seismosoft]

Adding imperfections on steel members is the way to introduce the initial displacements in order to model bucking.
The issue is beyond the scope of the forum, you probably need to discuss this issue with your supervisor or find a good textbook on steel structures.
Seismosoft Support

[Ralazem]

So you are saying that the introduction of a node in the middle of the bracing will model the imperfections?

[seismosoft]

It needs to be shifted a bit to the side (e.g. by 1%) so that to initiate the buckling of the brace.
Seismosoft Support