straight headed anchor bolts vs bent AB's
straight headed anchor bolts vs bent AB's
(OP)
1. Where in the codes does it say you can specify staight headed anchor bolts over bent anchor bolts? I know the research is in favor of straight headed bolts but I am dealing with some troglodites who say if it was good enough for my (you choose the person) its good enough for me or we have been doing this for 60 years and I am not going to change. I am looking for the research that supports this.
Jim
Jim






RE: straight headed anchor bolts vs bent AB's
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: straight headed anchor bolts vs bent AB's
I believe there is a bit of a reduction to the bent tensile capacities however. I'd start with Appendix D.
RE: straight headed anchor bolts vs bent AB's
Walking away from that, intuitive, anchorage after years of using it successfully is difficult. The hook helped in the setting of the dowels on the main reinforcing, too.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: straight headed anchor bolts vs bent AB's
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RE: straight headed anchor bolts vs bent AB's
RE: straight headed anchor bolts vs bent AB's
We never allow a bent anchor rod. If they come in bent on shops, we send it back R&R asking for straight anchors with nuts per our typical details.
RE: straight headed anchor bolts vs bent AB's
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: straight headed anchor bolts vs bent AB's
Mike McCann
MMC Engineering
RE: straight headed anchor bolts vs bent AB's
I understand the predictions for the load straightening the J bolt and pulling it out. My dissenters are saying that in 60 years of company history and hundreds of buildings it hasn't happened.
I do know that in 17 years of practice I have only seen 2 buildings that pulled columns out of or off foundations. One from an explosion of magnesium dust in the plant and one from a direct hit by a tornado. I believe the bent anchor bolts can pull out easier than the straight bolts.
I did see pictures of another case where the contractor who placed the foundation used 5 gallon buckets with the anchor bolts pushed into the concrete to provide the piers. In that case the building only lasted until the first decent wind (no where near a design event) and promptly fell over.
Again thanks for the responses.
Jim
RE: straight headed anchor bolts vs bent AB's
It is reasonable to assume that a short semi circle or a short section at the end of J-Bolt will facilitate crushing the concrete and ease the pulling out.
How about bigger bends? let us say converting the J-bolt to a large L bolt where the lower part of L is long? How about bent threaded bolts?
Without real data and proper experiments to support the claims it is hard to believe that straight is better than bent in absolute terms. May be the kind of bends we took for granted is where the problem and not the concept of bending the bolt or the rebar.
RE: straight headed anchor bolts vs bent AB's
Lets talk UNHEADED straight bars or LONG HOOKED bars.
Intuition says you will have a hard time pulling out an UNHEADED straight bar out of concrete if the bar is well embedded into the concrete. Current research IMPLIES that there is no calcs to support that intuition. But AISC says well, if your headed anchor is too short, go ahead transfer the load to the straight reinforcement ensuring development length.
There I get confused, why reinforce the insufficient HEADED with an unheaded straight or hooked.
I guess the whole thing against straight unheaded bars or bent bars has to do with incomplete research
respects
IJR
RE: straight headed anchor bolts vs bent AB's
Developing the straight, headed anchors into the pier reinforcing is invaluable and I don't see anything counterintuitive about it. This will only get you out of one failure mode check in App. D. (which is the concrete breakout), you still have to check all other failure modes.
For the headed anchor, we assume all load is transferred to the concrete at the head. If you develop the rebar above the plane of the anticipated failure surface then you've taken that failure mechanism out of the picture. What about this doesn't sit well with you?
The difference between a straight, headed anchor and a rebar is that a straight headed anchor is assumed to have all the load concentrated at the head, while the rebar transfers the load along its length.
RE: straight headed anchor bolts vs bent AB's