Pile Cap Design for 3 pile group

CRSI's pile cap design guide covers 3 pile groups. I wouldn't say it's much different than a four pile group unless you're loading it up eccentrically or are putting a moment reaction into the pile cap.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

Thank you TehMightyEngineer!

I was wanting to look at how the reinforcement detailing is done in case of the 3 pile cap. I understand from the design guide, that the steel shall be placed three ways. Is there a traditional procedure that is followed for this design?

I don't know how traditional it is but, nowadays, this will often be handled as a strut and tie design. Essentially a truss in the shape of a tetrahedron. To understand the bar layering, make a mental experiment of installing it. Effectively two layers with only two lines of reinforcing being truly level.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

The reinforcement does tend to be placed in three directions, between the piles. On thing to remember, and contractors don't always get this, is that the column needs to be at the centroid of the pile group if all three piles are to be loaded evenly.

The piles are generally arranged in a triangle and the reinforcement is laid in a triangular shape, with 1 layer joggled so the bars can be placed. Sometimes I have seen the 3rd layer detailed with a crank so the 3 layers can fit.