Shear Strength of a Concrete Drilled Pier
Shear Strength of a Concrete Drilled Pier
(OP)
Anyone have a reference that discusses the shear strength of a straight shaft reinforced concrete drilled pier (caisson)? ACI-318 specifically excludes them, but I have always used it anyway. Anyone know of another source?
Thanks
Thanks






RE: Shear Strength of a Concrete Drilled Pier
RE: Shear Strength of a Concrete Drilled Pier
I believe that, especially for caissons supporting lateral resisting elements and where shear and moment diagrams are provided by a geotech, ACI 318 is perfectly valid to use for the design of caissons.
I use ACI 318 to design caissons for shear and bending.
RE: Shear Strength of a Concrete Drilled Pier
RE: Shear Strength of a Concrete Drilled Pier
RE: Shear Strength of a Concrete Drilled Pier
RE: Shear Strength of a Concrete Drilled Pier
How close are you? Would a slightly higher f'c get you where you need to be? Do you have access to the break information for the caissons so you can see if the strength came in higher than spec'd?
RE: Shear Strength of a Concrete Drilled Pier
If I take everything into account that can help me I am around 2*sqrt(F'c) so bumping up the F'c even another 1ksi isn't helping enough.
RE: Shear Strength of a Concrete Drilled Pier
RE: Shear Strength of a Concrete Drilled Pier
RE: Shear Strength of a Concrete Drilled Pier
I would even go a step further and say that even if the bar were able to be fully developed in that 3" that shear friction doesn't apply to an inclined shear crack. Shear friction assumes a shear plane at some assumed crack location. An inclined shear crack is not a shear plane, it's a principle tensile stress plane.
It's the same reason you can't use longitudinal beam reinforcement at the ends for shear friction.
RE: Shear Strength of a Concrete Drilled Pier
RE: Shear Strength of a Concrete Drilled Pier
RE: Shear Strength of a Concrete Drilled Pier
If just at ground level you can still count slippage against the friction of the soil if a mat on the piles, or some passive push against the pile caps, if embedded ... of course if appropriate and permissible, that might not be.
You may also try to pass the shear as pure friction, i.e., a coefficient of friction to be developed between pile cap and pile. That of course would be forfeiting entirely the customary practice and usual intent and detail in RC construction, but the mechanism could be considered just to have some other appraisal of what available. Then it might be considered, would the piles stand the applied friction forces? A dynamic coefficient of friction would need to be considered if from earthquake. Everything here adventurous since not really a friction mechanism present, but of shear, and no clear real surface available for the friction.
RE: Shear Strength of a Concrete Drilled Pier
RE: Shear Strength of a Concrete Drilled Pier