Need a book? Engineering books recommendations...

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

RE: spacing limits for concrete beam shear reinforcement

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Thanks all.
Is there any practical or code limit on the minimum size of shear
stirrups?
For example, if W6.5 wire stirrups will work at 6" oc. for strength and
meet the maximum spacing limits, are there any other practical or code
considerations for sizing stirrups?

Christopher Banbury, PE
President

Ark Engineering, Inc.
PO Box 10129, Brooksville, FL 34603
22 North Broad ST, Brooksville, FL 34601
Phone: (352) 754-2424
Fax: (352) 754-2412
www.arkengineering.net

-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)umich.edu] 
Sent: Tuesday, February 12, 2008 11:46 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: spacing limits for concrete beam shear reinforcement

And I would futher note that the Masonry code (MSJC/ACI 530) has the
same
d/2 requirement...for both ASD and Strength design.

Regards,

Scott
Adrian, MI

-----Original Message-----
From: Kipp Martin [mailto:KMartin(--nospam--at)carollo.com] 
Sent: Tuesday, February 12, 2008 11:07 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: spacing limits for concrete beam shear reinforcement


Christopher,

If I remember correctly from my concrete design classes, the limit on
maximum spacing for shear reinforcing in beams is set so that any
possible
shear crack will intersect at least one stirrup.  That is where the d/2
limitation in 11.5.5 comes from.  Remember that shear cracks (diagonal
tension cracks) are at roughly 45 degrees to the horizontal axis of the
beam.  For shallow beams, this does indeed push the stirrup spacing
close.
As far as I know, there is no exception or variance to this requirement.
A
6" spacing does not sound like it is all that crowded.  It may not be
the
way the residential contractor "has always done it for 27 years" but it
is
not a new provision in ACI 318.  The oldest copy that I have is from
1983,
and the d/2 provision is in that edition as well.

--Kipp Martin, S. E., P. E.
  Carollo Engineers
  Portland, Oregon


>>> "Christopher Banbury" <cbanbury(--nospam--at)arkengineering.net> 2/11/2008 2:58 
>>> PM >>>
Perhaps someone can help us navigate the ACI 318 provisions and
exceptions
related to shear reinforcement spacing limits and area minimums.

When considering 12"Wx16"D c.i.p. floor beams on c.i.p. columns for an
elevated V-Zone residence, ACI 318, 11.5.5 requires stirrups at about 6"
oc
if d is taken to be 0.8*h. Based only on strength considerations, the
spacing could be 14" if No.3 stirrups are used. Torsion can be neglected
which helps with Av min per 11.5.6.3 but that doesn't help with the
spacing.

Are there any alternatives or exceptions to 6"oc stirrups short of
switching
to reinforced masonry which would does not have such restrictive spacing
limits? We are limited on height so increasing d is not an option.

I'm concerned that a stirrup spacing less than 12" oc would be
impractical
for the typical residential contractor.

Thanks in advance.

 

Christopher Banbury, PE

President

 

Ark Engineering, Inc.

PO Box 10129, Brooksville, FL 34603

22 North Broad ST, Brooksville, FL 34601

Phone: (352) 754-2424

Fax: (352) 754-2412

www.arkengineering.net <http://www.arkengineering.net> 

 

 

<http://usa.autodesk.com/adsk/servlet/mform?id=9131297&siteID=123112&CMP

=ILC-GN9219645015>  
<http://usa.autodesk.com/adsk/servlet/mform?id=9131297&siteID=123112&CMP

=ILC-GN9219645015> 

 



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   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 
******* ****** ****** ****** ******* ****** ****** ******** 





******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   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 
******* ****** ****** ****** ******* ****** ****** ******** 



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   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 
******* ****** ****** ****** ******* ****** ****** ********