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Re: Unblocked Plywood Diaphragm Deflection Calculation

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---------------------- 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>
cc:

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

Niaz



"Michael Valley" <mtv(--nospam--at)skilling.com> on 05/19/99 10:16:12 AM
                                                              
                                                              
                                                              
 To:      Niaz A. Nazir/EQE                                   
                                                              
 cc:                                                          
                                                              
                                                              
                                                              
 Subject: Re: Unblocked Plywood Diaphragm Deflection          
          Calculation                                         
                                                              






Mr. Nazir:

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.

-Mike


************************
> 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

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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