Orientation of hook anchor bolts

[SKJ25POL]

My basic question is, does the orientation of hook of hooked anchor bolts matter? if they are outward or inward? if all in same direction or some toward each other and some away ?
I know that is recommended not to use them but I wonder when they were allowed to use, if there was any requirement on the orientation of the hook.

Thank you

 

[TehMightyEngineer]

I don't know of any requirement but there are cover requirements that change the design strength of the hook. Looks up the stresses the hooks impose on the concrete and you can see where you need more cover. Obviously having hooks that overlap their high stress location is a bad idea.

For yours I'd either turn them all towards the center or orient them to be parallel to the face of the concrete (so they will all be 90 degrees from the adjacent one).

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[KootK]

I don't use hooks for serious stuff but, were I to, my preferences would be:

1) If there's a moment involved creating a T/C couple, point the hooks of the tension bolts towards the source of the compression. This suits the flow of stresses in the joint.

2) For all other cases, point the hooks towards the "meatiest" part of the member. More cover on the hooks usually improves capacity.

3) In all cases, consider congestion problems.

Pretty tough to enforce all this though. #3 is king on site of course.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[TehMightyEngineer]

I second KootK's note about the hooks. I avoid them as I've seen research showing headed anchors to be better.

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[sponton]

Yes, we avoid hooks or J bolts because there have been cases where they've failed because they got straightened somehow.
Some codes in high seismic zones [at least in the case of NZ and MX] specify that hooks [whether bolts or rebars/dowels] should be pointing inward, I assume because of the protected core.

 

[SKJ25POL]

sponton (Structural,

I assume you meant NZ is Newzeland and MX is Mexico?
My project is in U.S., do you know any old A.C.I or else code had any statement on the orientation of the hooks?

Thank you

 

[sponton]

ACI, Chapter 21, on seismic design.


So you see a reference, it's in McCormac's reinforced concrete book.

https://books.google.com/books?id=_...v=onepage&q=ACI hooks pointing inward&f=false

 

[sponton]

ok I didn't want to be lazy and I got nothing else to do so here it is:

21.10.2.1 Longitudinal reinforcement of columns and structural walls resisting forced induced by earthquake effects shall extend into the footing..

 

[SKJ25POL]

sponton (Structural,
Thank you very much buddy.
Just may I ask what edition / year ACI are referencing to?
Is it clearly says about the hook orientation?

I may not have that version/editon of code - may I ask for a big favor and if you have that particular page scanned possibly.
Million thanks

Respectfully,
SKJ25POL (Structural)

 

[sponton]

Here you go, ACI-318 chap 21.10.2 2006 version.

 

[SKJ25POL]

sponton (Structural,
Thank you so very much, very much appreciate it.

Have a good weekend
Thank you again

 

[KootK]

That ACI clause is essentially a version of the statement that I made above:

1) If there's a moment involved creating a T/C couple, point the hooks of the tension bolts towards the source of the compression. This suits the flow of stresses in the joint.

Hooked dowels in a common, concentric footing are likely to be well confined laterally regardless of the orientation of the hook. The issue is joint design for flexure as informed by srut and tie modelling etc. Essentially, the tension rebar is restrained from pullout by it's containing the opposing column compression force coming down into the knuckle of the hook (ish).

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.