Sway steel structure

[RRufino]

Hello all,

I was reading other topics and testing some procedures on steel portal frames and i'm not sure if the following procedure is correct for a sway portal:

1) make a buckling analysis proofing thas i'm in presence of a sway structure (as seen on other topics by calculating alfacr for global buckling mode)

2) change linear combinations to "P-Delta" (not large displacements)

3) set member definitions as non-sway and define proper buckling lenghts

4) run steel design

Is this correct?

Do i've to break columns and beams in order to have several intermediate points?

Thanks in advance,

Happy new year,

RR

[Simau]

Hi @RRufino 

could you specify what code you are using?

[RRufino]

Hi @Simau ,

I'm using Eurocode 3.

Tks.

[Simau]

I usually try to avoid alphacr < 10 for a global blucking.
So i can't tell you if your point 3 is correct.
You have to read carefully EC3 &5.2 &6.3
It's better if you have a concret example

[RRufino]

Thanks @Simau , me too but i'm evaluating an existing structure. It's a single portal truss where alfacr=7. Nevertheless i'm also interest in general procedure and robot approach to study further structures.

Thanks,

RR 

[Simau]

For what mode?

Could you post the structure deformation for this mode?

[RRufino]

Hi @Simau ,

As requested,

But as i said previously i'm also interest in general procedure and robot approach to study further structures.

Thanks in advance,

RR

[Simau]

@RRufino 

This deformation shape shows that there is a global buckling of the structure.
As I said you previously, I try to avoid Alpha cr < 10 by changing elements step by step to reach alpha > 10.
In case of existing structure With alpha-cr <10, I would try this ( but not sure @Krzysztof_Wasik 😞
Run a the second order with a “static analysis + P_Delta.” And check the displacements and resistance of the elements. The buckling lengths of bars are calculated according to your code using Robot features.