Fiber Section considerations

[Mohammadf]

Hi Dear all
when we use fiber section for a nonlinear element in a frame we consider what kind of interactions (such M-P, M-V, etc) and for which interactions we should use section aggregator command to fix fiber section deficiency?

regards

[Mohammadf]

Any Idea????

[mhscott]

With a force-based element, you can use section aggregator to couple P-M with V (or P-M-M with V-V in 3D) in the element equilibrium relationship bot not in the fiber model. For displacement-based, the aggregator doesn't get you anything, but you can try dispBeamColumnInt

[Mohammadf]

Thanks for your reply
so you mean that 1.if we have a nonlinear element with fiber section, we just consider p-m interaction. and for considering p-m-v interaction we have to use force base element with section aggregator command. am I right?
2.does section aggregator work for dispbeam column?

[mhscott]

With force-based, you can use aggreator to couple P-M-V in element equilibrium only, or NDFiberSection, which couples axial and shear stresses in fibers and thus element

Aggregator "works" for dispBeamColumn element, but it will ignore shear because it's not a Timoshenko formulation.

[Mohammadf]

thanks for your reply
I have another question in this category. when we use a material behavior to apply in a fiber section, this behavior works for which direction ( M, V, or P) for fiber section?
Regards

[mhscott]

I don't understand your question.

[Mohammadf]

I mean for example we use steel02 material to construct an I-shape section. is this material behavior works only for longitudinal direction of section fibers or shear or moment?
best

[mhscott]

Any uniaxialMaterial in a fiber section describes the longitudinal stress, so you get only axial and moment stress resultants.

[Mohammadf]

many thanks dear mhscott