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RE: Maximum inelastic displacement

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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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