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RE: Standard Portal Frame Analysis
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 Subject: RE: Standard Portal Frame Analysis
 From: Syed Masroor <masroor(nospamat)cstengrs.com>
 Date: Tue, 1 Nov 2011 06:44:22 +0000
Wow
We did this stuff at school. But the way it is reiterated here (no pun intended) I wonder if I could get through school if I had to do it again. Syed A Masroor Karachi, Pakistan From: h.d.richardson(nospamat)shaw.ca To: seaint(nospamat)seaint.org Subject: Re: Standard Portal Frame Analysis Date: Mon, 31 Oct 2011 23:48:22 0600 Thor,
I am assuming you want
to do this manually.
For a one storey multi
bay plane frame structure where the axial shortening of the second storey
"beams" permits only very small joint translation relative to the magnitude of
joint translation permitted by bending of the "columns" I would proceed as
follows:
1.) Pin a convenient upper storey joint (call it Joint
"A" for future reference) to provide the location for an
artificial horizontal reaction. Give Joint "A" a unit deflection
keeping the beams rigid.
2.) Calculate the fixed end moments (F.E.M.) for the columns
(note: the beams have zero F.E.M. because you kept them rigid in step
1).
3.) Now release the formerly rigid beams and do a moment
distribution analysis to determine all of the beam forces, moments, and
reactions you may need later, including the horizontal reaction at Joint
"A".
4.) The horizontal reaction at Joint "A" divided by the unit
deflection from step 1.) will give you a spring constant (lets call it
"k" for all horizontal (sidesway) movements.
5.) Analyze the structure from 1.) including the horizontal
reaction from Joint "A" for each of your actual load cases assuming no
initial deflection for Joint "A" to determine all beam forces,
moments, and reactions, including the horizontal reaction at Joint "A"
(call it Ra).
6.) The amount of sidesway will be Ra/k.
7.) The forces on your real structure (including the effects
of sidesway) will be the sum of (the forces and moments from 5.) + (Ra/k)*(the
forces and moments from 3.)
I have assumed a moment
distribution analysis because that is what I am most familiar with; but any
method of analysis should do.
Hope this
helps.
Regards,
H. Daryl Richardson
 Original Message 

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