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Minimum Edge Distance

Minimum Edge Distance

(OP)
Is there a minimum recommended edge distance from centreline of pile to outside edge of pile cap/grade beam? or from outside edge of pile to outside edge of cap/grade beam?

Dik

RE: Minimum Edge Distance

2
If you have a pile connected to the cap with dowels, you want enough distance for the longitudinal cap edge bars to pass outside the pile dowels.  Also, consider pile location tolerances in addition to the bar clearance distance.  We typically design 18" to 24" prestressed concrete piles or 24" to 48" steel piles.  With a plus or minus 6" pile tolerance, about 6" additional to get all the longitudinal bars past with 3" cover, we generally leave a foot from the outer edge of the pile in theoretical position to the edge of cap.  My experience is to be generous with this dimension.  On caps, rebar placement can be more expensive than concrete so make it easy for the
rod-busters.

Bob G.    

RE: Minimum Edge Distance

(OP)
Thanks SRE, but it's not the centre to centre spacing but the centre to outside edge of the cap that I'm curious about. I've typically used the bond development length of the rebar from the inside edge of the pile.

Dik

RE: Minimum Edge Distance

thread585-223592: Pile Edge Distance To Pile Cap

Dik

I have seen this dimension vary from 4" to 8" accros a variety of projects. I have seen 4" used for 2-pile pile caps and 8" for larger 6/8-pile pile caps. Personally, I prefer to keep the dimension 6" unless I am really trying hard to reduce concrete volumes. 6" in my opinion allows enough distance to gain sufficient development in the reinforcement when considering the 3" pile location tolerance.

Regards

RE: Minimum Edge Distance

Usually, single pile at the corner/side is checked for punching through the cap.  

Beside dimensional requirement, generally 1.5 times pile diameter is used for pile center to the outside edge of cap.  

RE: Minimum Edge Distance

(OP)
SRE... missed the 9" min. in your link.  I'll check that with the hook dev length...

kikflip... good link

STRE... design handbook for CSA A23 by PCA, has 2x pile dia... I don't know the source, but think it's excessive.  I've never encountered that large... 1.5x pile dia seems huge... 24" for a 16" dia pile.

thanks, Dik

RE: Minimum Edge Distance

The Florida Building Code (FBC) has this requirement

1808.2.4 Pile caps.
Pile caps shall be of reinforced concrete, and shall include all elements to which piles are connected, including grade beams and mats. The soil immediately below the pile cap shall not be considered as carrying any vertical load. The tops of piles shall be embedded not less than 3 inches (76 mm) into pile caps and the caps shall extend at least 4 inches (102 mm) beyond the edges of piles. The tops of piles shall be cut back to sound material before capping.

And in High Velocity Hurricane Zones (HVHZ)
1822.1.6 Reinforced concrete caps shall be provided for all pile clusters and such caps shall extend laterally not less than 6 inches (152 mm) beyond the extreme pile surface and vertically not less than 4 inches (102 mm) below the pile butt. Pile caps may be omitted when piles are used to support grade beams, provided that the spacing of Section 1822.1.4 is complied with, and provided that the portions of the grade beams acting in place of the pile cap shall be computed by a recognized method of analysis to properly carry the loads.

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