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RE: Column Splice Locations

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Greg,

Sorry for the late reply, but this one took a little looking into.  I don't
know if you have received a response yet.

Your interpretation is correct the lap splices are required to be in the
middle third of the column.  It appears that the 1997 UBC section 1921.7.2.2
is in error.  I say that because it is different in the ACI 318-95 section
21.7.2.2 and the Draft 2000 IBC section 1908.1.27.  Both of these documents
require the lap splices in the middle third if the factored gravity axial
forces exceed Ag f'c/10.

The ACI and IBC have additional requirements that kick in when the forces
exceed 0.35Po.  But the laps have to still occur in the middle third.

This additional requirement was a result of some performance issues observed
in the Northridge earthquake.

Regards,
Harold Sprague, P.E.
The Neenan Company
harold.sprague(--nospam--at)neenan.com


-----Original Message-----
From: Gregory P. Luth [mailto:gluth(--nospam--at)klaa.com]
Sent: Sunday, January 10, 1999 5:45 PM
To: SEAOC (E-mail)
Subject: Column Splice Locations


Section 1921.7.2.2 of the 1997 UBC applies to columns that do not resist
seismic loads, with axial load between 0.1 f'c and 0.3Po, in which the
compatibility moments due to Rw*delta do not exceed the design moment.
By reference to 1921.4.3, it appears that this section requires that the
lap splices in such columns be located in the middle 1/3, a significant
departure from previous codes.  Is my interpretation correct?  Can
anyone explain why this provision is not triggered for axial loads less
than 0.1f'c (1921.7.2.1) and for members with axial loads exceeding
0.3Po (1921.7.2.3)?