Poisson's effect in Hollow Cylinder Piles

[Scynot]

I'm Reviewing this paper (BEHAVIOR OF CYLINDER PILES DURING PILE INSTALLATION - Frank Rausche, M.ASCE1 and Scott Webster, M.ASCE2)on the causes of longitudinal cracking in piles and this paragraph stuck out for me.

"Poisson’s effect has occasionally been mentioned as a potential reason for
longitudinal cracking. However, hoop strain due to Poisson’s effect does not cause
stresses and, therefore, should not cause cracking. The authors have seen horizontal
strain measurement results that, as expected, ranged between 20% and 30% of
vertical compressive strain. Exactly, how the hoop reinforcement interacts with the
expanding concrete cylinder, particularly, since this cylinder is not uniform (grouted
tendon channels), could be part of an interesting study."

I'm having a hard time understanding this idea that transverse stress would be zero under vertical only load while transverse strain would be non-zero. how could you not expect any vertical cracking in the cylinder? any insight is appreciated.

 

[KootK]

I know zilch about this. So if somebody else shows up to play, go with their stuff.

For Poisson induced cracking to occur, there needs to be restraint to that cracking. In a solid pile, I'd expect that restraint to come from the natural attachment between the perimeter and the solid core. For a hollow thing with relatively small thickness / radius, I would anticipate that the thing would just expand relatively freely without cracking.

 

[1503-44]

That's it. Poison stresses in pressurized pipelines reduces the length of the pipe as its diameter expands. If the pipe is free to contract along its length, it does so without inducing stress. If the pipe ends are anchored, or the pipe is grouted or shear friction with soil holds it in place and it cannot freely shorten, Poissin stresses are induced. Thermal expansion or contraction acts similarly. If an element expands thermally, it will do so without creating stress, as long as it can freely expand. Restrain it and its likely to break something, either itself, or whatever is restraining it.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."