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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?

2009-09-15, 11:11 AM	#1
huangyhg 超级版主注册日期: 04-03 帖子: 18592 精华: 36 现金: 249466 标准币资产: 1080358888 标准币	p-delta effect in etab programm 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? __________________ 借用达朗贝尔的名言：前进吧，你会得到信心! [url="http://www.dimcax.com"]几何尺寸与公差标准[/url]