Hi, I am working on a simulation of built-up section using two angle sections, I want to run the model i.e. initially load should take by one angle and then second angle should get active to take load. actually this is to represent retrofitting for existing structure.

I have used Model Change option to deactivate all elements except one angle and reactivate in the next step, But after reactivation it was not running and showing the following warnings (See Images).

Can any one suggest me, how to run my model? Thank Youuuuuuuuuu