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

Re: Concrete Column Biaxial Bending

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Scanning through my reference book in reinf concrete,
the value of Pno can neither be exceeded by Pnx nor
Pny. With this in mind the result using the reciprocal
load method will always be a positive number.

Rod Tayong 


 
--- Rich Lewis <seaint02(--nospam--at)lewisengineering.com> wrote:
> I am working on the design of some concrete columns
> with biaxial bending.  I
> don't do a lot of these so a program like PCA Column
> is not feasible.  I am
> using the ACI Design handbook, Example 8, as a
> reference.  It is the
> reciprocal load method.  This is one of the 3
> methods discussed in PCA Notes
> for the ACI 318.
> 
>  
> 
> I made a MathCAD sheet for the procedure.  It worked
> fine for the example
> problem.  Most of my columns worked fine.  I had one
> column where the method
> kind of blew apart on.  It occurred on a column with
> low bending moments.
> When you calculate the values for Pnx and Pny using
> the equation
> Pnx=Rn*fc*Ag*h/ex, it becomes very large due to the
> low eccentricity.  I
> used the minimum eccentricities of 0.6+0.03*h or b.
> Same for Pny.  When you
> run the equation 1/Pni=1/[(1/Pnx)+(1/Pny)-1/Pno] you
> get a negative number
> because of the high Pnx and Pny.
> 
>  
> 
> Is there a valid range where this equation works and
> doesn't?  Am I
> miss-applying it?
> 
>  
> 
> I created another MathCAD sheet using the load
> contour method and the column
> design had no problem.
> 
>  
> 
> Thanks for your insight.
> 
>  
> 
> Rich Lewis
> 
>  
> 
> 


		
Yahoo! Mail
Stay connected, organized, and protected. Take the tour:
http://tour.mail.yahoo.com/mailtour.html


******* ****** ******* ******** ******* ******* ******* ***
*   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 
******* ****** ****** ****** ******* ****** ****** ********