Load Deflection Curve

[NessaArya]

Hello,

I am modelling a concrete column in ABAQUS and I don't understand the load deflection curve that I get.
The curve reaches a maximum load, decreases and increases again. An image of the curve is attached.

Can someone explain this behavior?

Thanks!

 

[Mustaine3]

I assume you've run the analysis displacement controlled...?

Was NLGEOM activated? Check also plasticity (and maybe damage) parameter, buckling, kind of snap-through effects, hourglassing, ....

 

[NessaArya]

Yes, I run it displacement controlled and use velocity with smooth step.

NLGEOM is activated to take second order effect in consideration.

Thank you for your tips about activating enhanced hourglass control an. I got a better curve.

But now I have another problem. The new curve doesn't reach yielding and the maximum load exceed the expected max load!?

 

[DrBwts]

Densification?

 

[Mustaine3]

Or maybe the hourglass controls make the elements too stiff. Use a better mesh or suitable elements, so hourglassing does not appear.