Sleeve Nuts Vs. Turnbuckles

[MacGruber22]

I am finding some publications that believe sleeve nuts are easier to install and less expensive than turnbuckles. Also, Portland Bolt indicates turnbuckles are not a stocked item. Obviously if the aesthetics of the turnbuckle are desired, it doesn't matter.

Thoughts?

-Mac

 

[ajh1]

A turnbuckle has reversed threads at the two ends. This allows the rod to be tightened by turning the turnbuckle if the end connections, typically clevises, do not have adjustability once installed. If the rod connection at the end is adjustable (rod through a plate with a nut on it), then the turnbuckle would not be required. A sleeve nut is going to have a single thread orientation all the way through, great for using multiple rods to build up an overall length, but not length-adjustable. I would concur that a sleeve not is probably both easier to install and less expensive, it simply can't do all the functionality of a turnbuckle. There are a variety of manufacturers that make turnbuckles of various sizes and capacities. We happen to use Cleveland City Forge and have been happy with them for many years.

 

[Leftwow]

I would like to join this discussion because I have read literature that says tension cables and steel rods are being phased out of steel construction, and not many engineers use them. However, I find the concept fascinating and would like to learn more about the design of these, since there are many bridges that use steel cables... anyone have some insight on that?

 

[MacGruber22]

Sleeve nuts also have reverse threads.

http://www.portlandbolt.com/products/nuts/sleeve/

Thanks, ajh1


-Mac

 

[sbisteel]

I suppose the advantage of the turnbuckle is that the inside threads are exposed, allowing you to nick the threads and prevent the rod from backing out.

 

[JAE]

Turnbuckles provide you with more distance to adjust tension in the rods (vs. sleeve nuts).

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[CANPRO]

installation wise, not sure there is an advantage of one over the other - not that I've heard anyway. I believe sleeve nuts are generally shorter than turnbuckles and would provide slightly less adjustability. sbisteel raises a good point about being able damage the threads and lock the connection in place.

 

[KootK]

I would like to join this discussion because I have read literature that says tension cables and steel rods are being phased out of steel construction, and not many engineers use them.

I can't speak to bridges but, in buildings, this has certainly been a trend that I've noticed and wondered about. Many braces that would have been rod & cleveis when I first started out seem to be chevron etc now. I have a few theories:

1) Seismic. Rod bracing doesn't play so great with seismic in many situations.

2) Base anchorage details. We pay much more rigorous attention to this stuff than we used to. Consequently, it's harder to make the numbers work and there is often a benefit to sharing your shear load between two column bases instead of one.

3) Braces in walls. I see a lot of braces buried inside of cold formed stud walls rather that positioned behind those walls. As such, the braces need to be able to take wind and that tends to steer one away from rods.



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.

 

[hokie66]

I was not familiar with the term "sleeve nut" until reading this thread. But they are just a different type of turnbuckle. The advantage over most commercially available forged turnbuckles is that they are stronger. The typical open turnbuckles you buy off the shelf often are not as strong as the rods they connect.

These sleeve nuts, often custom fabricated from bar stock, are used in many architecturally exposed applications. Airport terminal buildings come to mind.

 

[MacGruber22]

I suppose the advantage of the turnbuckle is that the inside threads are exposed, allowing you to nick the threads and prevent the rod from backing out.

That is a good point.

Turnbuckles provide you with more distance to adjust tension in the rods (vs. sleeve nuts).

Agreed, though I would think you could make up the difference at clevises. I wonder what the maximum brace length would be practical for a given sleeve nut length and rod diameter. My braces are at most 12 ft long. I haven't sized my rods yet, but I imagine they will be in the 1" dia. range.

hokie - I didn't realize they would be stronger.

-Mac

 

[ajh1]

The coupling nuts we use on occasion are continuous thread, not reversed thread at one end.
The other advantage of the turnbuckle is you can clearly see how far the rod has been threaded into the part. It would seem there would be a risk on the sleeve nut that after adjustment you would not necessarily have enough length of thread in the part. This might be particularly true if you start out with it a little loose and intend to tighten to snug up the rod. If you fully thread it in before you start to insure enough depth of thread then you don't have any adjustment left.
Cables seem to be phasing out and I would say good riddance, too much stretch under load without return to original length.
Rods are good for lighter loads. I wouldn't recommend them for extremely heavy loads nor for conditions like crane bracing where you would see a lot of cycling loads, or at least 0 to something back to 0.
As seismic forces are getting higher there is a desire to move up to more ductile systems, i.e. eccentric braces, buckling restrained braces, etc. which generally require tension and compression braces which drops rods out of the picture.

 

[MacGruber22]

thanks, ajh1. I certainly agree with the sentiments regarding seismic.

-Mac