Geometric imperfections, Buckling analysis SAP2000

[rleclercq]

Hi,

I am currently studying a simple model V&V with SAP2000. I managed to compute buckling analysis, but I want to compute buckling analysis with geometrical imperfection (L/1000) to compare the value with the code equation Cr=AFy/((1+lambda^2n)^(1/n)). To include the imperfections, I tried to applied a lateral load corresponding to the shape of the mode 1. Is it the best way to include imperfections ?

Thanks for your answer,

Raphaël

 

[JoshPlumSE]

If you're doing an Elastic Buckling analysis then you should directly model the imperfections? You want them included in the initial stiffness matrix.

 

[rleclercq]

Do you mean model imperfections manually ? I tried with curved frame but results are not as expected. And it's seems really long because I want to do a sensitivity study about the initial imperfections effects.

 

[JoshPlumSE]

Yes, I mean manually adding in the imperfections. I'm not sure how SAP models curved members. So, I was really talking about breaking the member into at least two pieces so that you can offset the joints to the initial imperfection you were looking for.

 

[UcfSE]

If you want to capture the imperfections in the buckling analysis you will need to model the deflected geometry, not the ideal geometry, as Josh says.

 

[JasonMcKee71]

Imperfection can be imposed by many ways such as:
[ul]
[li]modeling of the deformed geometry[/li]
[li]apply horizontal loading[/li]
[li]do nothing as imperfection will be introduces because of the small arithmetic errors within the computer calculations, such as 1e-10[/li]
[/ul]

Jason McKee
proud R&D Manager of
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