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RE: Maximum inelastic displacement

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The last sentence of the last paragraph of the 1999 Blue Book 
commentary for C108.2.9 Item 1 (page 137) says (at least to me) 
that there are situations where it  ** is **  apppropriate to include 
diaphragm deflections in the delta-M calculation.  

Dave Evans


From:           	Gerard Madden <gmadden(--nospam--at)duquette-eng.com>
To:             	"'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
Subject:        	RE: Maximum inelastic displacement
Date sent:      	Thu, 8 Nov 2001 17:43:01 -0800 
Send reply to:  	seaint(--nospam--at)seaint.org
Organization:   	http://www.seaint.org

> Mark,
> 
> The drift is not calculated using diaphragm deflections. It is a measure of
> the vertical resisting elements displacements relative to a floor above or
> below.
> 
> The diaphragm displacement should be calculated using the values from the
> metal deck manufacturers ICBO. (I know Verco has values in their ICBO for
> unfilled metal deck) They also give limits for diaphragm deflection based on
> the type of wall (Concrete or CMU) supporting the boundaries of the
> diaphragm.
> 
> You should be able to look up Verco's ICBO report at www.icbo.org and type
> verco in the search field.
> 
> Diaphragms , when flexible (as it sounds in your case (diaphragm deflection
> is 2.5 times or more than the displacement of the vertical resisting
> elements)) shall be designed using an R value not greater than 4.
> 
> Hope that helps,
> -Gerard
> SJ, CA
> 
> -----Original Message-----
> From: Matt Melcher [mailto:MattM(--nospam--at)lbdg.com]
> Sent: Thursday, November 08, 2001 5:05 PM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: Maximum inelastic displacement
> 
> 
> Let's say I'm trying to determine the maximum inelastic displacement of a
> building at the midpoint of the diaphragm.  It is a shear wall building with
> a metal deck roof, therefore the diaphragm displacement is considerably
> greater than the wall displacement.  
> In determining the maximum inelastic displacement(Delta-m), would you
> include the displacement of the diaphragm as part of the Delta-s? This total
> number would then be multiplied by 0.7 and R to determine Delta-m(UBC
> 30-17).  This would seems odd to me since the diaphragm has little or
> nothing to do with the type of lateral system.  What is an appropriate R
> factor (if different) for metal deck diaphragms?
> Any Ideas?
> Thanks in advance
> Matt Melcher, P.E.
> 
> 
> 
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