Buckling of deformed structure

[IGG1980]

Hi there!

Let's introduce my self. My name is Igor and I'm mechanical engineer. I solved lot of questions thanks to you, but all my questions were questioned by others. Until today. I have worked lot in SOFISTIK but, now I have to learn to make some calculations in SAP2000. I use to make calculations on steel structures like this (unfortunatelly not this one, but that kind)

So, I know how to introduce my models from autocad and make some analisys in SAP2000, but i have to make some buckling calculations i don't know how.

First of all, I want to make some linear buckling analisys to achive the shape of the structure of those modes i want to analyze. After that, I'll give the structure some deformation (maximum L/250 being L span leght) as geometry imperfection, with exactly the same shape I achieved in the linear buckling analyisis. Finally, I'll make nonlinear buckling analisys with this deformed structure. This procedure, for every mode i want to analyze.

My questions are: how can I give that geometric imperfection to my structure? How can I see how far is my structure from buckling, i mean, is there any Buckling Load Factor (BLF or something)?

Than you so much.

Best regards

 

[stressed]

You can introduce imperfections to an idealized structural model by either modeling the structure in a way in which members are out of plumb, or you could assign joint displacements, or assign load (some codes call this "notional" loading) in order to add imperfection. If you add imposed joint displacement or loading, you would need to run a P-Delta case with the load or displacement and then sequence one or more buckling cases to be run based on the P-Delta case.

You can define a Buckling case, or run buckling as a nonlinear P-Delta case with large displacements.