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RE: Column reinforcement splices

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I think moderate seismic means zone 2 and the code does not have specific
seismic lap splice requirements [UBC at least doesn't].


In a high seismic [zone 3-4 or SDC D by IBC]:

When columns are part of the LFRS in zone 3 and the axial load is less
.1*f'c*Ag then d/4 or 4" oc transverse reinforcement is required over the
lap length and the laps can't occur in the joints or within 2*d of the joint
per 97 UBC 1921.3.2.3.

When columns have axial load >.1*f'c*Ag and are part of the LFRS, splices
need to be mechanical or welded unless they happen at midheight between
floors and are proportioned as tension splices per 97 UBC 1921.4.3.2. [99
ACI318 21.4.3.2 requires the lap splices to be enclosed but not specific in
UBC].

If the columns are non-LFRS and Pu>.3Po and they work for stresses induced
by deformation compatability with the LFRS then they need to meet 97 UBC
1921.4.3.2 too and 1921.7.2.2 requires ties at 6" oc max full height.


-----Original Message-----
From: John Holliday [mailto:john.holliday(--nospam--at)chemtex.com]
Sent: Tuesday, February 26, 2002 10:31 AM
To: seaint(--nospam--at)seaint.org.
Subject: Column reinforcement splices


This seemed a silly question but I have got several
different opinions from my associates.
We are building a large industrial facility overseas where
labor is very cheap. On our design drawings we indicated
column reinforcement splices at floor levels and offset
the bars from the lower level to accomadate the upper bars
(aci318/99 7.8.1.1). The civil contractors (we are in
process of bidding the work) have told us that that is not
how column splicing is done over there. Because material
is so expensive, they use the full length of bar (40
feeet)whenever possible and make the splices in the column
where ever the bar ends. Additionally they do not offset
the lower bar at the splice, they make a normal lap splice
with bars placed next to each other. They are required to
stagger all column splices, 33% of splices at level one,
33% at level two one meter above level one and the final
33% at 1m above level 2. These practices result in the
column splices occuring anywhere along the length of a
column. It appears to me that these splices need to be of
the offset kind with ties added at the splice to account
for the horizintal component of the offset bar. Is their
method of using normal lap splices feasable? These are #10
and #11 bars in columns within a building 130 feet tall in
a medium seismic area.
Thanks in advance for all input.
Regards,
John Holliday P.E.

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