Second order effect and frame imperfections

[KillianPMG]

Hi guys,

I've attached an snip from an SCI design guide below.  I'm designing a tall steel braced building. Bracing is in the form of K-frame therfor tension and compression.

I'm trying to understand how to conduct full second order analysis and any limitation with using second order analysis in Robot.

If I select non linear and p delta effect in analysis parameters, is it correct to assume robot accounts for:

• frame imperfection, so I do not have to apply notional horizontal loads (EHF) as per eurocode 
• second order effect due,to the deformed geometry, is accounted for in the analysis.

Are there other settings or important points I should look out for when running a second order analysis in Robot 2015.

My building is 40m high, each column has nodes at approximately 6m centres ( from research I believe it important to have internal nodes to run non linear, p delta analysis).

Thanks for your guidance.

Killian

[Rafal.Gaweda]

I think p delta effect in analysis parameters is correct to be assumed.

[KillianPMG]

Rafal,

Thanks for your reply.

So I can just select p-delata analysis box and leave the non lnear box unticked.

Regards

Killian

[Rafal.Gaweda]

pdelta+nonlin will be ticked

[mustafahesenow · Accepted solution]

1

[t.sautierr]

"frame imperfection, so I do not have to apply notional horizontal loads (EHF) as per eurocode "

Maybe I missed something in RSA, but i think it is not performed automatically -> you have to set this effect manually even when pdelta is ticked.

[t.sautierr]

"1- Consider (P-Δ and P-δ) Effects ( flexural, shear and axial deformations).

2-Consider the initial Imperfection whether by direct modeling of that Imperfections pf structural members or by inclusion of notional loads.

3-Reduction on the member stiffness to remove the partial yielding due to residual stresses in the members which is creating destabilizing effects."

What difference you make between P- small delta and 3)? To me 3) is related to push-over analysis and is not taken into account even when p-small delta is ticked?