Precast Conc. Pile Connection for Gravity Load 1

[STR04]

What are your thoughts for not connecting a precast concrete pile to the pile cap when the loads are gravity only. I'm working on a design/build project and the contractor want's to save money by eliminating the epoxy anchors typically required to connect the two systems. I currently show the detail with a 6" embedment and no rebar to connect the two. I'm in a high seismic zone so I'm a little concerned about the lateral.

TIA

 

[civilperson]

Surround the upper tip of the pile with the reinforcing grid, place bottom steel 3" clear of bottom of cap and thus contain the pile.

 

[hokie66]

Don't know why you are talking about epoxy anchors. The way you connect precast concrete piles to the pile cap is to break out the concrete of the top of the pile and use the pile reinforcement to tie the two elements together.

 

[STR04]

hokie66,

Interesting thought. How do you work with the prestress tendons after they are exposed? I seems like it would be easier to cut the entire pile off and then come back and drill & epoxy. This give you something nice and clean to work with but really I cannot say since I'm not a contractor and you have used this detail because this is what the contractor wants. If you had say a 50kip tension pile, do you think you could still use this type of detail? Is this a standard detail from PCI?

 

[hokie66]

STR04,

Sorry, I should have told you that I am commenting from an Australian perspective. Most of our precast piles used in building work are reinforced with deformed bars rather than strands. So the typical detail is to saw around the pile, break out the remainder, bend the bars if required, and construct the pile cap. Yes, 50 kip tension can be taken in one of these piles.

Having said that, there are plenty of buildings on timber piles, and probably some on concrete piles, without positive connection of the piles to the pile caps. I think that would be a definite no-no in high seismic areas.

 

[shin25]

Few years back, University of South Carolina, Columbia, SC did some experimantal program to study how does the plain embedment of prestressed piles into the footing or caps behave. You can find a copy of this report in July-August, 2001 PCI journal.

Their recommendation was, if the piles need to develop their nominal moment capacity, their plain heads need to embedded about 12" into the footings of caps.

Hope this helps.

 

[BENDOG]

I am currently working on a project where we are using concrete filled pipe piles with a Seismic Design Category of "C". IBC 2003 Section 1808 specifies the seismic design requirements of pile connections to pile caps for different types of piles based on your Seismic Design Category. If you are to conform to IBC I suggest you read this.

 

[STR04]

What if you're in the state of California and the code (2001 CBC) doesn't state the specific requirement? I know the new 2007 CBC will reference IBC but for now I'm stuck between a design/build contractor and my boss.

 

[UcfSE]

If you have no guidance legally, listen to the man (or woman) who signs your check.

If they want to eliminate the epoxy anchors, then make them provide something else. I would tell them you have to have something and ask what they would prefer to what I have shown. You can't just take out something you specified or you'll get hammered for over designing. They could question every little thing after that and say you're just overdesigning and costing them money, such-and-such needs to be removed. Even if it works, make them change/add something.