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Biaxial Pier Stem Design

Biaxial Pier Stem Design

Biaxial Pier Stem Design

(OP)
Is there any widely accepted design methodology for pier stems on isolated footings with large biaxial bending moments?
Can the stem be designed as a doubly reinforced beam with moments in each direction being independently analyzed?
 

RE: Biaxial Pier Stem Design

You will have to do a interaction (strain-compatibility) analysis because your pier will probably also have axial loads in addition to biaxial moments.

Any good column design software such as PCACOL should be able to do the job.

RE: Biaxial Pier Stem Design

(OP)
Slick-
Its an odd situation....
There are very high moments with almost negligible axial load....hence I'm not so sure a "column" design is even appropriate.
I think what I basically have is a cantilever beam with biaxial moments.
I'll admit, I am a steel guy with some basic foundation design knowledge and this is a first for me.
I am very familiar with "normal" spread footing design as well as concrete beam design theory.
Would designing this as a cantilever biaxial concrete beam make sense? If so, is a regular bi-axial interaction equation like you'd find in steel appropriate?

Thank you

RE: Biaxial Pier Stem Design

PCS Column is still an appropriate (not to mention efficient) design/analysis tool for this case. PCS Col will give you the interaction diagram whether you have axial load or not. If you have no axial load then look at the interaction diagram (surface when you have biaxial bending) for Mx and My with P=0.  

RE: Biaxial Pier Stem Design

(OP)
Is PCS column some kind of software?

RE: Biaxial Pier Stem Design

Sorry, I meant PCA Column. That's what I get for typing on my phone.

RE: Biaxial Pier Stem Design

(OP)
Still interested in a by-hand technique.

RE: Biaxial Pier Stem Design

It is the same as a biaxial column (even though it has little axial load).  For low axial load the recommended hand method is the Bresler Load Countour Method (or its extension the PCA Load Contour Method).  See p7-10 thru 7-22 of the -05 PCA notes for procedures.   

RE: Biaxial Pier Stem Design

(OP)
Thank you Willis  

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