Return to index: [Subject] [Thread] [Date] [Author]

column detailing

[Subject Prev][Subject Next][Thread Prev][Thread Next]
BACKGROUND INFO:  I have 48"x12" reinforced concrete gravity-load-only
columns.
The columns are not part of the lateral force resisting system.
The lateral force resisting system is reinforced concrete shearwalls.
The building is in UBC Seismic Zone 2.

QUESTION:  Does the UBC code require that I space stirrups @ d/2 min. for
the entire length of the column?

Section 1921.2.1.3 requires that the columns be detailed per Section 1921.7.
I interpret the minimum requirements of Section 1921.7 to be that transverse
reinforcing must be spaced at d/2 for the entire length of the column. For a
48"x12" section, d/2 is about 4 1/2."  Additionally, if the column is
moderately or heavily loaded. The required stirrup spacing is even tighter
(3").

This detailing requirement seems to be excessive in light of the fact that
detailing requirements for actual seismic frames in Zone 2 are required to
conform with 1921.8, which is LESS stringent than 1921.7.  Also ACI 318-95
does NOT require ANY special detailing for non-lateral-force-resisting
columns, as long as you are not in a high seismic design category, i.e. Zone
2. The columns only need to conform to the basic requirements of Chaper 7.

I also don't understand the reasoning for detailing a gravity-load-only
column to perform with a highly ductile response, given that the lateral
force resisting system is r/c shearwalls.  Provided the shearwalls are
designed correctly, in a design seismic event, there is no way the
gravity-load-only columns will experience large deflections or large
deflection-induced forced.

Please comment, thanks!
Evan


* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org