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RE: Delta sub m

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DELTAm from the special load combinations are intended to give the maximum
force the system can deliver to critical elements. 

DELTAs used for drift calculation is not supposed to be from the ASD load
combinations with Eh/1.4.  1997 UBC 1630.9.1 errata
[http://www.icbo.org/Building_Standards_Online/read.cgi?file=./Code_Applicat
ions/archive/909094434.archive&action=Code_Applications] says to use 1612.2
strength load combinations with Eh [no /1.4] to figure DELTAs, there is a
typo in the earlier printings that says use 1612.3 load combinations with
Eh/1.4 for ASD.

The story drift .7*R*Eh is supposed to be an approximation the maximum
inelastic drift.



-----Original Message-----
From: Samir Ghosn [mailto:sghosn(--nospam--at)harris-assoc.com]
Sent: Monday, August 19, 2002 11:56 AM
To: seaint(--nospam--at)seaint.org
Subject: Delta sub m


Hi 
Just want to find out how some of you view the displacement value
associated with special seismic load condition outlined in  the seismic
provisions equation 4-1,
1.2D + 0.5 L +omega E for OMRF, two story, R=4.5.  do you consider the
resulting deflection equivalent to delta sub M. i.e.( inelastic)???
My first reaction was to view detla s associated with with equation 12-10,
).9D +E/1.4 or .9 D -E/1.4. as elastic delta s. with corrosponding deltaM =
0.7xRxDelta sub s.  In fact the maginfication factor seems to indicate
inelastic behavior. I am concerned about the vlaue of delta sub M as
compared to allowable drift values.
Your insight is appreciated.
Samir Ghosn, P.E.
Harris & Associates
(1800) 827-4901xt 360



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