Concrete Piles extension in Pile Caps or Raft

[Robert-32]

Dear Colleagues,
Do you know why should a pile penetrate the cap by 3"? Can we Weaver this in some cases? Or it is a must?

 

[dik]

I don't know... it's been common, almost forever. I don't know if it's to fully engage the top of the pile or to provide some modicum of corrosion resistance.


-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Robert-32]

Thank you dik,
Do you think that the above requirement differs when we are talking about Raft on Piles? The code states "Pile Cap", does that include Raft on Piles?

 

[dik]

Nope, same conditions occur... with large interior slabs, the soil beneath tends to desiccate. This can have an impact on highly plastic soils, and maybe even affect their load capacity as well as increasing the load a tad.


-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[KootK]

I think that the 3" is mostly about:

1) accommodating tolerance in the top of pike elevations

2) providing a bearing mechanism for shear transfer between piles and caps.

3) getting 3" cover on the cap bottom bars which are often set directly on the piles.

All of these goals can be achieved by different means and, if they have been, I would consider the 3" discretionary.

 

[OldDawgNewTricks]

All of these goals can be achieved by different means and, if they have been, I would consider the 3" discretionary.

Depends on what code you are using. IBC 1810.3.11 requires 3" minimum embedment.

 

[bugbus]

50 mm embedment is typical in Australia.

I think the main reason is to fully encapsulate the top of the pile for durability reasons. The top of the pile will never be flat or built exactly to the correct level.

 

[KootK]

Depends on what code you are using. IBC 1810.3.11 requires 3" minimum embedment

That wouldn't change anything for me in the context of dealing with a non-compliant field condition which I assume this to be. In such situations, and where I feel that I understand the pertinent issues underlying the code provisions, I deem my professional judgement to supercede the code. Naturally, it's also the AHJ"s prerogative to deny me that if they feel differently.

If a pile comes up an inch short, I'm certainly not going to abandon it or order some meaningless extension if I can get what I need from the joint as is.

 

[OldDawgNewTricks]

I didn't gather from the OP that the question only regards dealing with a non-compliant field condition (maybe because I'm unfamiliar with the term "Weaver"). Even so, I think I would try to adjust the design of the pile cap to maintain the required pile embedment.

 

[dik]

I like the attitude... one of my favourite moments was one in a judgement for a building collapse in Bancroft, Ont. several years back. The judge commented on my "cavalier application of the Ontario Building Code". The collapse load was only a few psf over the actual measured and calculated dead load. It was just 'so far' off code. I had to use Euler's bucking to indicate the failed structure had any strength. It was a long span wood truss system and the contractor had put the web bracing on the wrong members.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[KootK]

Maybe it's a Canadian / prairie thing... Our regulatory environment is a tad slacker that some other environs.