pile caps - helical piles

huangyhg

pile caps - helical piles
can anyone provide some guidance regarding pile caps for helical piles.  it will be a single helical pile for a t-pole pipe support.  the moment is relatively small.  the cap and pile will see tension and compression.  i beleive i need to consider the same failure modes as that for an anchor bolt. is there concern for bending in the pile?
yes, the pile has to be adequate to resist combined axial and bending.  for your application, the pile cap would likely be a steel plate with four or more bolts which would match the holes in the t-pole baseplate.
ba
so the load is transfered directly from the base plate through the bolts to the pile? i thought pile cap would be designed such that the plate on the pile would be embedded in the cap a sufficient depth to develop the full tension load from the bolts.  
if the cap plate on the pile can be set level and to the required elevation, the pole baseplate bears directly on the pile cap plate.  the bolts just hold them together.
you can use a concrete pile cap if you prefer.  that allows grouting of the t-pole baseplate and does not require so much accuracy in the placement of the pile and leveling the cap plate.
ba
for this type of footing i have always used a concrete pile cap.
the typical top detail for the piles is a square top plate with a tube that is bolted over the top of the helical pile tube. this provides the embedment for tension.
provide square shear links in both directions around this cap plate and then provide chemical anchors to the top. this gives tolerance for both top of pile and pile location which is very critical for any interaction between structure and foundation.