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Turn Buckle and Rod Design

Turn Buckle and Rod Design

Turn Buckle and Rod Design

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

RE: Turn Buckle and Rod Design

RE: Turn Buckle and Rod Design

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.

RE: Turn Buckle and Rod Design

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

Welp, back to the drawing board?

RE: Turn Buckle and Rod Design

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.

RE: Turn Buckle and Rod Design

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

RE: Turn Buckle and Rod Design

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

RE: Turn Buckle and Rod Design

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

RE: Turn Buckle and Rod Design

klaus,

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

RE: Turn Buckle and Rod Design

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_ro...

RE: Turn Buckle and Rod Design

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

RE: Turn Buckle and Rod Design

(OP)
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?

RE: Turn Buckle and Rod Design

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

RE: Turn Buckle and Rod Design

@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

RE: Turn Buckle and Rod Design

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

RE: Turn Buckle and Rod Design

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.

RE: Turn Buckle and Rod Design

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

RE: Turn Buckle and Rod Design

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

Dik

RE: Turn Buckle and Rod Design

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.

RE: Turn Buckle and Rod Design

Kingpenn3:
You said....., “The loading on this system is approx. 20 kips. The system is going in a school gym behind glass curtain walls.” That being the case, you may want to pay some special attention to bldg. drift up at the top, under load, as this relates to the rigidity of any glass and glass curtain wall system. Tie rods allow a fair amount of movement of their upper connection points before they pick up their design load, due to slack take-up, due to geometric and stress/strain length changes and this can have detrimental effects on any rigid cladding system.

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