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Need a formula for shear strength of a pipe

Need a formula for shear strength of a pipe

Need a formula for shear strength of a pipe

(OP)
I just got asked a question I hadn't heard before. I need to know the shear strength of an 48" RCP pipe buried 12 feet to invert in what i believe is saturated soils. The pipe will be lined with CIPP. I know the Flex Modulus, Flex  Strength and Tensile Strength of the liner.  

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: Need a formula for shear strength of a pipe

I think this is maybe not an easy question to answer (at least without more information).  I would think the shear strength would be dependent on the many varied constructions available for such pipes and by different specifications/mfgr etc. (e.g. dimensions and amount/orientation of steel reinforcments etc.), as well as the actual condition of the materials now in th epipe wall (at least if this is an existing/old installation?)

RE: Need a formula for shear strength of a pipe

RE: Need a formula for shear strength of a pipe

Dick,
I'm not sure there would ever be enough confinement to mobilize the shear strength of the whole pipe cross section, except possibly within the bell of a joint.  But that would also require rigid confinement of the bell, which isn't likely in saturated soil.

Typical shear is not a failure mode for which the pi;e is tested or required to meet under ASTM standards.  Pipe load capacity is based on load testing under a crack width criterion.

The Concrete Pipe Design Manual of the American Concrete Pipe Association does not list shear strength as a variable, a parameter, or a criterion for any of the pipe characteristics.

RE: Need a formula for shear strength of a pipe

Ron makes a good point.  Typically RCP strength is based on the d=0.01 based on psi and classification of pipe.  There is a section on structural design based on bedding material in the design manual.  I am not sure if you can dl a PDF of the manual, I got a disc with the pfd on it.

RE: Need a formula for shear strength of a pipe

(OP)
Thanks Guys. I don't think the Engineer writing the spec. has any idea of what apipe does under load. I'm going to ignore him until I can't. Then maybe I will ask him how to do the Calc.  

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: Need a formula for shear strength of a pipe

Dick...good move.  He probably wouldn't be able to rebut if you challenged him.

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