Pile rebar projection, hooked or not?

[J1D]

On the c.i.p. concrete pile std dwg, we usually provide two details of dowels to the contractors. 1. straight, the dowel is the extention of the pile vertical rebars. 2. hooked (90 degrees or 180 degrees) with other end embeded into the pile concrete. My question is, in construction practice, which one is better (or popular)?

In my understanding, straight dowel in the first case is required when the pile embedment depth is a variable because overlap may be inevitable. But the problem thus is the pile-cap shall be much deeper to accomodate the straight projection.

Thanks in advance for comments

 

[rowe]

The preferred method would be "1. straight". This method takes advantage of continuity at the pile to cap connection, which is important for seismic consideration (where plastic hinges may occur).

Your 2nd detail allows the contractor an easy "fix" if the pile is embedded beyond the expected elevation, which is OK if formation of a hinge is not a consideration.

If formation of a hinge is a consideration, you might consider detailing a lap splice near the mid-height of the column, with a long enough lap to allow for variance in the embedment depth (i.e. if your min. splice length is 54" then detail a lap splice of 54"+24" to allow for the column to extend 2' further than anticipated)