Triangular Reinforcement Pattern for Strut and Tie Pyramid

[canwesteng]

I have a pile cap sitting on three piles, triangular to distribute loads evenly to the piles. My S&T model is basically a 3 sided pyramid. I'm going to lay the rebar out in a tringular pattern, but I'm wondering if there is any basis for laying the bar out in an orthogonal pattern, and then taking the capacity of the ties as the sine/cosine of the angle between the ties and the rebar. Any thoughts?

 

[hokie66]

That would be acceptable, but I think the more traditional placement of bars in a triangular pattern, from pile to pile, is simpler.

 

[canwesteng]

I think triangular is much easier for analysis as well. I've just always defaulted to using either 2 larger piles or 4 smaller piles instead of 3, so I wasn't sure if triangular reinforcement is common.

 

[hokie66]

Triangular has never been an issue when I have designed it that way. The only slightly tricky bit is to ensure the column is at the centroid of the 3 pile group.

 

[canwesteng]

I don't think getting the column in the centre is going to be hard, unless you mean during construction. I'm adding 2 inches of eccentricity in the S&T model to allow for them misplacing the piles.

 

[hokie66]

I meant getting the piles in the right place. The column will be on a grid line, but the piles in one direction will be offset differently from a grid line so the centroid of the pile group coincides with the grid. Simple, I know, but sometimes set out wrong if not clearly shown on the drawings.