topic Re: Second order effect and frame imperfections in Robot Structural Analysis Forum

Second order effect and frame imperfections

KillianPMG — Sat, 24 Jan 2015 11:46:12 GMT

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

Re: Second order effect and frame imperfections

Rafal.Gaweda — Mon, 26 Jan 2015 13:50:44 GMT

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

Re: Second order effect and frame imperfections

KillianPMG — Mon, 26 Jan 2015 14:10:50 GMT

Rafal,

Thanks for your reply.

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

Regards

Killian

Re: Second order effect and frame imperfections

Rafal.Gaweda — Mon, 26 Jan 2015 14:26:25 GMT

pdelta+nonlin will be ticked

Re: Second order effect and frame imperfections

mustafahesenow — Sun, 05 Nov 2023 05:29:44 GMT

Re: Second order effect and frame imperfections

t.sautierr — Sun, 01 Mar 2015 07:25:26 GMT

"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.

Re: Second order effect and frame imperfections

t.sautierr — Sun, 01 Mar 2015 07:27:18 GMT

"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?