P-delta

[Jhno]

Hi,
in the generic 2D frame NL push-over analysis example of the OS wiki, when defining the geometric transformation for the column, it is mentionned that p-delta might be used to consider p-delta effects.

Got me curious cuz I assumed in my model that vertical loading + linear geom. trans. in lat. push-over would take p-delta effects in consideration

Considerer a simple vertical beam with vertical load applied at the top node to simulate the weight. If I apply an incremental lateral load at the top node, will the p-delta effects be considered?

From what I understand, under the action of the lateral force the point of action of the weight will move hence create an excentrated force (which will create a force + moment) ... which is the p-delta effect.

If am correct; what are the advantages of the p-delta geom. trans??
If am wrong; could you point me to a explanation (or provide it?)??
Thanks for the help!

[ismailqeshta]

You can test it. Just use Linear transformation in the same model, and then change it to P-Delta. You may notice that at large deformations, the model with P-Delta undergoes smaller base shear at the same deformation. This is due to the effect of P-Delta that you considered.

[Jhno]

Thanks for the answer.


I modified it in my NSP model.
When I run the analysis without p-delta for column versus p-delta I get the same curve in the pre yield part of the base shear - roof drift curve.
At break point (I assume to be max V), the two curve are different (not that ,much thouth). However, p-delta curve keep running for larger value of deformation than the linear transf.

so pdelta is more accurate?

[ismailqeshta]

P-Delta will basically consider the additional moment on columns caused by the gravity load at large lateral deformations. So, yes it is.

[Jhno]

Aight, I see. Thanks for the help!