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Re: Footing design

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Dear Santhosh,
If you have Joseph  E. Bowle's book of Foundation Analysis and Design, refer Page no. 364 , 4th edition, you can see the solution of your problem. I will repeat the formula here.
q=P/A+My x/Iy+Mx y/Ixx. Use + or - at the locations of sign +. This is applicable if there is no separation of footing.
Regards
Ashraf


 
On 30/12/05, Santhosh Kumar Yedidi <sant527(--nospam--at)gmail.com> wrote:
I have a rectangular footing in the X-Y plane. There are Moments Mx ,
MY and vertical compressive force Fz. Its clear how to do for uniaxial
bending. But then for biaxial moment how to design.

The normal procedure we follow is,
We calculate maximum/minimum stress due to MX and Fz in X dir (i.e
Fzy/A + (Mx * (Lx/2))/Ixx  and Fz/A - (Mx * (Lx/2))/Ixx
Similarly we calculate maximum stress due to My and Fz in Y dir. (i.e
Fz/A + (My * (Ly/2))/Iyy  and Fy/A - (My * (Ly/2))/Iyy
And we design for shear and flexure in both the directions with the
stress calculated.

But i feel we are not taking into account of the affect of Mx in Y dir
or My in the X - dir. So can one tell some methodology

Santhosh

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--
S.M.Ashraf
Structural Engineer
Al Habshi Consultants Office
P.O.Box 27154
Safat 13132, Kuwait
Tel. 965-2430103