Grade Beam to Pile Torsion Connection

Right over the pile is the last place I would omit the stirrups.

Agree with WARose,

I'm with A all the way

Thanks guys. A colleague has actually convinced me that it is possible, and probably preferable, not to have a stirrup group centered on the pile. See below. A curious feature of this model is that you go from having a tubular torsion truss model to having just a pair of up/down trusses on either side of the grade beam as it hits the pile. I'm working on a version that maintains the entire tube. It's just wickedly hard to draw.



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.

It's preferable not to have any re-bar at all, but not advisable. I use to do a lot of beam-column joints as per ACI 352, and looking at your situation that way (as a column-beam connection; I don't know what the magnitude of the other forces are), you typically were limited to stirrup spacing at 4-6" at the joint (especially for Type II joints were stress reversals and inelastic behavior from seismic was expected).

That may not be the most accurate way to look at your situation....but no stirrups at such a connection would unnerve me a bit.

I was originally comparing it to a beam column connection too WARose. And that's what lead to my initial concerns. Upon closer inspection, however, having an infinite extent of concrete on either side of the joint facilitates some STM options not available in a typical beam-column joint.

Some of what would have had to happen within the joint in a beam-column joint can take place beside the joint instead. It introduces some eccentricities but those are easily handled. At least, I think that's the case. It does unnerve me a bit too.

The trouble is that, with a circular pile, one has almost no control over where the vertical reinforcement will land. Planning a dense arrangement of stirrups right over top of the pile is asking a lot in the field.

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.

I don't know if it will help you but in my drawings, I allow the contractor to skew the beam torsion ties that pass through the pile dowels. There's really no other choice. If your beam is big enough, you can use lap splices to close your ties and they're easier to install. We've even used welded A706 ties in a couple circumstances - last resort but can save the day.

Long live headed dowels. Imagine hooks up there.