Turn Buckle and Rod Design

[kingpenn3]

Could someone share a good reference procedure on design of turn buckles and rods?

 

[Trenno]

Link

 

[hokie66]

Keep in mind that most commercially available turnbuckles are not rated for the full strength of the rod. Generally, if you need full strength, you have to fabricate your own.

 

[bowlingdanish]

I always just assumed they were for site tolerance/installation and you designed a standard rod.

Welp, back to the drawing board?

 

[dhengr]

Kingpenn3:
What are the turnbuckles and rods intended to accomplish? You really didn’t say. As Hokie mentioned the/some turnbuckles may not be rated at the same cap’y. as the rods which fit them, and of course, you should limit your design strength to the strength of the weakest link. There are several different grades, strengths and sizes of turnbuckles from different suppliers. And, I certainly wouldn’t buy my turnbuckles from the local big box store if strength was important.

 

[kingpenn3]

The rods and turn buckle will be used as tension members in a braced frame under seismic loading.

 

[oldestguy]

If in doubt buy a few different ones and have them tested to tension failure to give an idea of the ultimate strengths.

 

[klaus.]

Turn buckles are usually part of a specific system from a specific company
Once you pick the tension rod you can pick the turn buckle as well as end connections from the catalog
So all parts belong to the same 'system'



best regards
Klaus

 

[hokie66]

klaus,

That may be true for light stuff, but is not typical for structural bracing.

 

[klaus.]

no...I am talking for heavy construction stuff ...big ones with lots of load

see here for example

http://www.mconnect.eu/en/application/practical-contruction-elements-for-statics.html

and many others



best regards
Klaus

 

[hokie66]

klaus,

That company looks like it has a well thought out system, but I imagine it operates primarily in Europe. I don't think that system or similar is typical of other parts of the world.

Anybody else here who would routinely specify these rods? They look good, but I think their application is in high end structures, airport terminals and the like.

http://www.mconnect.eu/images/Downloads/tension_rods.pdf

 

[thaidavid40]

We do a lot of industrial design work, and turnbuckles in that sort of environment tend to see a lot of abuse. For that reason, I typically limit turnbuckle/rod loads to only 20% of the ultimate turnbuckle capacity.
Dave

Thaidavid

 

[kingpenn3]

The loading on this system is approx. 20 kips. The system is going in a school gym behind glass curtain walls. I don't think it should see a considerate amount abuse. The AISC Table 15-6 does specify loading for rods and turn buckles.

thaidavid40, are you saying you typically use only 20% of the loads specified by the manufacturer or the loads specified in the AISC manual?

 

[klaus.]

If you take a 'system' of one of the suppliers you dont need to worry about the turn buckle
it is part of the system...



best regards
Klaus

 

[thaidavid40]

@kingpenn3 -
I'm saying, "20% of the ultimate turnbuckle capacity." Most manufacturers list their "safe working strengths" in the typical online data. If you order from them, they will supply an ultimate (usually tested) strength. Apply the 0.20 resistance factor multiplier to that number.
Dave

Thaidavid

 

[PengStruct]

I've specified rods and turnbuckles in a braced frame using the AISC manual but for wind bracing, never did it for seismic.

 

[ajh1]

I would emphasize the fact that a lot of "standard" turnbuckles do not have the capacity to reach full capacity of a 50k brace rod. However, there are companies that can provide a full seismic-capable, rod-strength level, turnbuckle. We use Cleveland City Forge for turnbuckles that achieve this.

 

[chicopee]

I use Crosby turnbuckles but strictly for rigging application regardless of cost.

 

[dik]

Can you use a specialised curved washer and a nut on the end? Likely less costly and is common in these environs.

Dik

 

[UcfSE]

The AISC Manual 15-6 uses a factor of safety of 3.00. This is a typical value for a static structure in which the load is a wind load. Turnbuckles are also used for dynamic and impact applications in rigging and other situations. In that case I would use a factor of safety of at least 5, and preferably also in line with a more rigorous lifting code such as the ASME BTH (below the hook) code.