Compression dev. length -- precast to CIP connection

[JKStruct]

I'm working on my first big precast job (parking garage), here's my situation:

A 24"x24" PC column needs to be supported on a 5'-0" CIP pilaster above the ramp at the 1st floor. It's supporting the entire building. I've designed the pilaster to be slightly oversized (40"x24") to avoid interference/crowding with the anchor bolts from the column and the pilaster reinforcement. I need a fair amount of compression steel in the pilaster to make it work (12-#9). My question is about compression development length.

Usually, I develop the compression steel into the column above, but this isn't possible for this condition, due to the precast column. I need the steel for compression immediately upon load transfer to the pilaster, so how do I ensure development of the compression reinforcement? Or do I even need to worry about developing the rebar at this interface if I provide confinement ties (which I am, anyway)? Developing the compression steel into the foundation is easy (and necessary). I'm just trying to think about the condition at the top. Would providing a Lenton Terminator, or similar mechanical device at the top of each bar be sufficient? Then, do I need to worry about the 2" of concrete between the Lenton anchor and the top of the pilaster? I'm out of ideas.

Thanks in advance.

 

[csd72]

Do you actually need to use the compression capacity of your bars? By the sound of things you have plenty of concrete to take the compression load at the top of the column. Yuo then may only need enough embedment to hold it in place and tie it in (depending on seismic situation).

But if you have bending at the top then you will need to develop tension capacity.

I dont think that those lenton terminators were developed for compression, they could punnch through the cover concrete.

 

[civilperson]

If the bars are not directly under the column, they do not need compression development. Check bearing capacity of the concrete face of the pilaster compared to the maximum axial load in the column. The excess of column compression quantity needs to be taken by steel reinforcement under the column.

 

[Teguci]

If you designed your column with a pin connection at the CIP to PC interface, then all you need to do is provide anchor bolts for shear and as called for in ACI 318. Precaster will be able to tell you how to show the baseplate for the precast column.

If you need to transfer moment at this interface, use NMB splices or similar.

Call your local precaster. They are very helpful and will lead you in the direction of their standard practice.