---------------------- Forwarded by Niaz A. Nazir/EQE on 05/20/99 10:59 AM
Niaz A. Nazir
05/19/99 10:26 AM
To: "Michael Valley" <mtv(--nospam--at)skilling.com>
Subject: Re: Unblocked Plywood Diaphragm Deflection Calculation (Document
link not converted)
The specific problem that I am working on is:
176'x84' diaphragm, 1/2" plywood with 10d @6,12, unblocked and chorded,
You will see that comparing the two eqns., equation 8-6 and 8-7 have nail
slippage and chord slippage components which are independent of the force v
(subscript: y. )In addition the shear deformation is also present.
Using eqn. 8-5, all kinds of diaphragms will calc out to be stiffer than
the blcoked plywood diaphragms.
For now, I have resorted to using ATC-7-1 and triservices manual..
I appreciate your help
"Michael Valley" <mtv(--nospam--at)skilling.com> on 05/19/99 10:16:12 AM
To: Niaz A. Nazir/EQE
Subject: Re: Unblocked Plywood Diaphragm Deflection
I am a member of the Project Advisory Committee for the effort to
update FEMA 273 (and make it into a Standard). Could you give me
more information concerning the real case you are calculating (L, b,
etc.)? That would give me a place to start looking. As you noted,
equation 8-5 does seem to leave out significant sources of
flexibility that appear in equations 8-6 and 8-7. I can't promise
immediate resolution, but I'm willing to look at your problem and at
the specified procedure in more detail. I will then share your
concerns (and mine) with the rest of the Project Team.
> From: "Niaz A. Nazir" <NAN(--nospam--at)eqe.com>
> To: seaint(--nospam--at)seaint.org
> Date: Tue, 18 May 1999 17:14:10 -0700
> Subject: Unblocked Plywood Diaphragm Deflection Calculation
> Reply-to: seaint(--nospam--at)seaint.org
> Organization: http://www.seaint.org
> I am trying to compare the FEMA 273 equations for the deflection
> computation of blocked and unblocked plywood diaphragm
> The unblocked diaphragm stiffness is given by equation 8-5 with a G
> (subscript: d) value of 800,000 or 400,000 (FEMA 273)
> The blocked diaphragm stiffness is given by equation 8-6 & 8-7 (FEMA 273)
> Using these equations will yield unblocked diaphragm stiffer than the
> blocked one......
> It appears that the equation 8-5 may be incomplete and missing the web
> shear defection contribution. Using ATC-7-1 one could compute unblocked
> diaphragm stiffness which calcs out to be much less than FEMA 273.
> Any comments, suggestions???
> Niaz A. Nazir, PhD, PE
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Michael Valley E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc. Tel:(206)292-1200
1301 Fifth Ave, #3200, Seattle WA 98101-2699 Fax: -1201