p-delta effect in etab programm

huangyhg

p-delta effect in etab programm
hi everybody
we have building with 45 floor in define all load
fc ,ceiling and wall ....etc
but for the effect of p-delta
i need to confirm about p-delta load combination
is that right?
1.2 dead +1.2 floor cover +1.2 wall +0.5 live +earth quick
also
what is the factor effect on the number of interative?
i'm pretty sure etabs will not iterate at all.  it uses a story geometric stiffness matrix to account for second order effects.  no matter how far it moves, the story force won't change, so the geometric stiffness matrix won't change, so it's done in one iteration.
other programs, sap for example, use element geometric matrices.  because individual elements' axial forces change due to second order effects, programs that operate like that must iterate.
as for the load combinations, there will be a large set of combinations that must be considered, 1.2d+1.6l for example, just to name one more.
etabs does iterations, you can also set the convergence tolerance and/or maximum iterations.
interesting.  does it always iterate during second order analyses or only if "large displacements" is turned on?