J Hook with Bolt

[EngineeringEric]

I have a client who wants to install a single pole sign (typical to gas station signs). So with the Anchor Bolts undergoing tension i would design the AB to be 1" headed (hex or square) F1554 with 25" embedt. And the client has some 54" J bolts on hand... So i explained how the extra length doesn't mater once the bottom hook straitens out and becomes a smooth dowel. that is 54" long. One thing we mentioned was adding a bolt and washer at the end of the j-hook so when the hook tries to pull up the head will resist this motion by pushing into the center of the pier.

Now i am not sure how to analyze this . I know the failure mecanism of the sideways force but the logic seems to be the bolt will only engage when the confined Hook straitens which cannot straiten with the headed bolt.

I was hoping one of you could shed some light on the matter if this is a crazy idea, a bad idea, and why.

Thank you

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[CELinOttawa]

This is one of those counterintuitive times where longer and bigger can be weaker and worse... The bolt calcs may (quite rightly) tell you that the longer bolt will fail the foundation's concrete at a much lower load unless you increase confinement. Also you cannot design a terminated J-hook anchor as a straight or regular J-hook answer. I've not seen a report detailing how to design them, but I can tell you from personal experience that playing with anchor bolt shape a d layouts can have very surprising and unexpected results.

Try to find some research paper or design guidance dealing with this arrangement. My money's on Restreppo or Eigenhousen (sp?) having done something on this. I have a fair number of anchoring design guides; I'll see what I can find once I get home.

Just as an aside: My first reaction would be to advise the client/owner that the unknown is dangerous in this business and to cut down the J-hook anchors to straight anchors that will do the job.

 

[a2mfk]

Many years ago I went to a workshop at Simpson where they installed and tested several concrete anchors. One of the was the now notorious J-hook. It straightened out and snaked right out of the hole as predicted. Changed all of our details the next day and never looked back.

The epoxy bolts installed with adequate embed depth failed the steel. It was impressive.

 

[dik]

Can you cut the bend off and add a heavy hex nut?

Dik

 

[dhengr]

Cut the hook off and sell it for scrap and chalk the rest up to a learning cost. Add a thread, a nut and a sufficiently sized washer and some confinement reinforcing and you have a real anchor bolt.

 

[EngineeringEric]

Thank you gentlemen, It seems to be a consensus on my gut that this is not a good idea. I Think it will be best to cut to bottom and add a bolt per standard detailing. I suppose i will call out the minimum length and let them decide whether it better to buy new and keep these for a future job where they can find an application to use these massive J-Hooks.

Thanks for the information!