Hooks in Pile Caps

[VAengr]

CRSI design handbook states, "the provision to include a 180 (degrees) end hooks or heads on all reinforcing bars in pile caps with single lines of piles around the column is a prudent precaution against a premature "tied-arch" shear failure mode". What does "single lines of piles" mean?

 

[grantstructure]

I'm going to suggest that they mean a pile cap in which there are only piles in one "layer" or line around the perimeter. A 4x4 group with a column at the center, for instance, as opposed to a 16-pile cap in a 4 rowx 4 column array. The latter would have more than one "line" of piles around the column, and therefore the loading won't take the form of a simple arch between the column load point and the piles at the edge.

 

[TXStructural]

Grant is correct. Bars in the direction where a pile cap is acting as a single span have the most concentrated stress near the end of the compression strut The 2009 CRSI Design Handbook specifies that all bars should be hooked or headed on pile caps with 2, 3, 4, 5 6 7, or 9 piles. For caps over 8, 10, 11, or 12 piles, only the bars in the short dimension need to be hooked or headed, and they should be on the bottom layer.

While not always mandatory, final design for most pile caps should be developed using strut and tie (primarily to satisfy shear requirements of ACI 318-11 15.5, which references Appendix A.) We are working on revisions to the CRSI Design Handbook to incorporate this change.

 

[WillisV]

@TX - as long as the updated methodology ends up with the exact same thicknesses and reinforcing that have been in CRSI for the past 30 years we should be good!

 

[VAengr]

Thanks for your replies.