Tack weld nut vs headed bolt 1

[delagina]

Does this affect anchor bolt embedment.. looking at my spreadsheet and there're nothing there if it's tack weld nut on threaded rod as opposed to headed bolt

 

[canwesteng]

It doesn't have to affect embedment, but it could if not spec'd properly and you give the contractor length of rod and not distance from TOC to anchor head.

 

[Whoopdedo_LSU]

How much thread engagement do you need? why would tacking welding either take away from your threads for thread engagement. Use a weld stud?

 

[wannabeSE]

Is this a trick question? If the work is based on ACI 318, look at the code to see how effective embedment is defined.

 

[BUGGAR]

Maybe it's your spreadsheet? Look for the one by AWS that covers welding situations.

 

[dik]

I use plain rod and thread 1" on the end and tighten the nut to the end of the thread... when you tighten the nut on the anchor rod, any rotation wants to push the rod into the concrete and force the thread onto the rod that isn't threaded.

No weld required...

Dik

 

[delagina]

My spreadsheet was developed by PIP which was based on ACI appendix D.
I dont see anything about it in appendix D.
This is more of a curious question.

Our preferred anchor bolt is headed per our standard but Ive seen threaded rod with tack weld nut also being used. I'm not really when it's preferred to use one over the other.

 

[Agent666]

Ensure your bolt material is actually weldable as well. Generally high strength threaded rods are not weldable due to hydrogen embrittlement.

 

[dik]

And if you use ASTM F1554, in grade 55, you have to stipulate it is weldable. the 105 stuff isn't.

Dik

 

[dhengr]

Delagina:
My old/std. go-to detail was pretty much as Dik suggested, a headed bolt or a plain round bar threaded at each end, and with a nut and washer on the embedded end. Our A.B. had to be cut to length and then threaded on both ends, and a nut and washer added. The bolt head, or nut and washer are intended to increase the end bearing area and thus the size of the conc. failure cone or area. I think that threaded rod has kinda become the default rod since it has become, more or less, a commodity item which can be roll formed in long lengths and then cut to any length for use, without the ability or effort of threading the ends. There should be nothing wrong with welding a nut to the end of a A.B. as long as the rod and nut are weldable, and the welding is done on the outer end, not the interior surface. And, you as the engineer/designer should make that determination before you spec. this detail. Generally, you should not be welding on high strength and heat-treated nuts and bolts because this can do metallurgical damage and reduce their strength. Your spreadsheet is based on ACI appendix D, a concrete code, so why would it spend much time on steel items details of us? It is your job and responsibility to marry the two materials with good engineering knowledge, experience and judgement.

 

[BridgeSmith]

If there is adequate room, using 2 nuts tightened against each other could work in lieu of tack welding the nut, if welding is not feasible, or not convenient.

 

[Lomarandil]

Or for that matter, punching the threads (there's a better term I'm forgetting) to lock the nut

----
The name is a long story -- just call me Lo.

 

[jimstructures]

Lo

upsetting the threads is how we term the process

Jim

 

[Lomarandil]

That one!

----
The name is a long story -- just call me Lo.

 

[12345abc6ttyui67]

If I got punched I'd be pretty upset about it too.

 

[BUGGAR]

Also saw a spec for marine bolts: "Bolt threads at the head of the the nut shall be peened with a 1/4" dia. punch to a depth of half the thread depth. Such peening shall occur at two locations on each bolt."

 

[Once20036]

Our preferred anchor bolt is headed per our standard but Ive seen threaded rod with tack weld nut also being used. I'm not really when it's preferred to use one over the other.

Is this a question about smooth rod vs threaded rod?
There was some good conversation here:

https://www.eng-tips.com/viewthread.cfm?qid=339117

Personally, I don't use threaded rods for anchor bolts regardless of whether the nut on the threaded rod is tacked, peened, punched, upset, or otherwise unhappy.

 

[BridgeSmith]

"I'm not really when it's preferred to use one over the other."

Threaded rod has the advantage for installations with odd or varying length, and is sometimes preferred for installations that require an embedded anchor plate, etc. to be secured to the bolt. we use them for our pole anchorages because we have an anchor ring embedded at the bottom with nuts top and bottom of the ring. Bolts are not threaded the full length of a 4ft anchor bolt, so we can't use bolts.

OTOH, bolts come in a higher grade, so have increased strength for the same size. They're also simpler to install for embedment, since there's no tack welding, peening, punching, etc. to keep a nut in place. Also, no question of whether the nut actually got installed.

 

[dik]

Why peen or weld. When you are tightening the anchor rod, the nut, if jammed to the end of the thread cannot move and the end of the anchor rod is pressing into the concrete? I rely on the bottom nut being forced 'tight'.

Dik

 

[BridgeSmith]

Dik, I think we're still discussing how to secure a nut to an all-thread anchor rod.