Do purlins need to be modeled in staad

Hi,

Can you pls help.Image may be NSFW.
Clik here to view.

I modeled the purlins in the shelter and results of displacement and moments are ok,

but when i removed the purlins it resulted in larger deflection and moments.

My question is it ok to model the purlins inorder to consider its stiffness?

Or not to model the purlins inorder to not account its stiffness?

Which of the two scenarios is the correctt one?

Thanks a lot.

See also attached sketch.