Bolt Subject To Pure Tension Load 1

[Robert_spider]

Hi To all,
I have a question to be asked I know how to calculate the bolt capacity for Tension and Shear, also how to check bolt bearing against different elelment such as Steel or Aluminum.

I want to ask if there is a hanging bolt by which a bar is hanging and the bolt subject to pure tension loads.
How can I calculate the force will make the bolt to fail the thread and come out of the nut.

 

[phamENG]

The threads on a bolt and in a nut are designed to preclude this type of failure. So long as your hardware is coming from a reputable source, it should not be an issue. If it's not coming from a reputable source, there probably isn't much point in engineering it anyway.

If you know how to calculate the bolt capacity for tension AND shear, you already know how to calculate the capacity for tension. You have to do it to do the combined, elliptical interaction equation already.

 

[rb1957]

if the nut strips, the bolt (loadpath) fails.

typically nuts have a higher allowable than the bolts, so not an issue.

Of course you could create a design when the nuts are weaker than the bolts (steel bolt and Aluminium nut) and you have an issue
I've had this situation ... steel fasteners into a helicoil in an Aluminium plate. I considered the tapped hole to be like an Aluminium bolt of the same thread.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[BridgeSmith]

I agree with what phamENG and rb1957 said, with one caveat - the nuts have to be the proper grade and type for the bolt tensile strength.

Nut Compatibility Chart

 

[Robert_spider]

Thank you all for your response, sorry for asking silly question. But let me answer some points here:

The Blue Hanging Bar is of Aluminum Grade 6082 T6,
The Bolt is Grade A2-70 (The Dia has to be decided)
The nut will by Nylock of same grade.
i have load of 10 kN Ultimate.

I know if it is even 10mm threaded bar of grade A2-70 this applied load is less than the Tension Load Capacity of the Bolt.

But we are thinking to use M12 bolt, but I just want to check by calculation the the thread failure.

@phamEng I do know how to calculate Shear and Tension Capacity, these bolts are in Tension Loads not shear load as the Shear is carried and transfer by the THICK T of grey color in the diagram.

But I don't understand what did you say here ''you have to do it to do the combined, elliptical interaction equation already'''.

 

[SWComposites]

Frankly, with a hanging detail like that shown, it is very poor design practice to have the bolts be the critical failure mode, or if they are, the bolts should be oversized such that there is no question about their strength.

 

[Robert_spider]

That is not my design @SWcomposites,
this the traditional practice for Unitized system in façade engineering.
The Dead Load Carried By the Hanging Bar, Control and Taken by the Bolt To the Floor Bracket.
While the wind load is transferred through the T to the bracket.

 

[phamENG]

I'm most familiar with steel - carbon steel mostly but some structural steel for SS and Aluminum Structures (I don't usually mess with aluminum bolts.) When bolts are loaded in tension and shear, you calculate the tension capacity and compare it to the tension load, then you calculate the shear capacity and compare it to the shear load, and then you enter it into the 'elliptical interaction equation"...so called because if you plot the function it it forms an ellipse. So...unless you're using some other form of capacity check, which is certainly possible as different countries/regions rely on different codes and application can vary between industries...if you're checking shear and tension together, you already checked tension alone before you did the combined check.

 

[Robert_spider]

@phamEng
I wonder How to call you Sir, Buddy, Engineer
So, You missed the fundamental I described The bolts are not taking and Shear Load.

And assume there is bolt which is in both in tension and shear It will go through 3 checks which you are right.
1st Check the tension capacity of bolt against the applied load.
2nd Check the Shear capacity of the bolt against the applied shear load.

3rd Check the combine shear and tension capacity of the bolt, (There is a combined capacity checking equation in the euro code).

 

[phamENG]

phamENG will do.

And no, I didn't miss it. You're saying you don't know how to check for only tension, but you somehow know how to check for both tension AND shear. I'm saying that's nonsensical. If you know how to check for both, then you know how to check for Tension. You can't check for both without fist checking for tension. So please, explain how you can check both without checking tension.

 

[dik]

and if the load is subject to vibration, I'd be using a thread locker like Loctite...or 'wrecking' the threads.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Robert_spider]

@phamEng

Sir, you have understood me wrong I apologize for any misconception.
I do know how to check all three checks for bolt.
But this question has arise that what if the Nut fails and the bolt slips through the nut.

@dik yes the nut is loctite which is Nylock.

 

[jjl317]

Having worked for many years in unitized curtainwall / facade, I can't say as I have ever seen an anchor like this.

Is the bolt truly a bolt (with an integrated head), or a threaded rod, threaded/tapped into the bar?

Does the bolt adjust the location of the "hanging" bar vertically, with the "tee" passing thru a slot in the brown (likely aluminum) anchor component?

Two US based potential references that might help -

a)the Aluminum Design Manual - ADM (includes information on capacity (pullout, pullover, bearing etc.) of threaded connections, plus typical analysis information)
]b) AAMA TIR-A9, which specifically addresses design considerations of metal fasteners for cladding, including stainless, aluminum and carbon steel components.

 

[Robert_spider]

@jjL317

Is the bolt truly a bolt (with an integrated head), or a threaded rod, threaded/tapped into the bar? Threaded Rod, but not tapped into the bar no threads in the bar.


Does the bolt adjust the location of the "hanging" bar vertically: YES this is second purpose for making adjustment according to site levels.

with the "tee" passing thru a slot in the brown (likely aluminum) anchor component? T has two functions one to get bolted with the UNITIZED frame plus it can freely move up and down for leveling (by sitting on blue hanging bar) and to transfer the wind load directly the floor bracket.

 

[jjl317]

Thanks for the clarification on the how it's used.

Does the threaded rod have nuts and washers on both ends (above and below)?

 

[Robert_spider]

@jj

at The bottom which is not visible in the image it has a head like bolt, at the top which is visible in the image there is a Nylock Nut.
Why I am saying it is a rod because it very long apologize if I am wrong here as well.

 

[rb1957]

sorry, but who cares if the nut fails ? I mean, it has such a low probability of occurring that no "professional" would consider it.

Sure we'd consider it if there is some obvious difference that would make that loadpath critical (like an Aluminium nut on a steel bolt)
but if it is a steel nut on a steel bolt (of the same grade) why would the nut fail ?

We consider loadpaths and analyze the critical ones (and the ones near critical). In this example I'd consider the bolt (and lets assume that covers the nut, same grade of steel) and the pull-thru of the various plates, and further afield as necessary.

If you're saying "no, I need to consider failure of the nut" then add a third bolt and show that any 2 can carry the load (and assume that failure of a bolt/nut is readily detectable, or inspected for).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[BridgeSmith]

All that's required to preclude failure of the nut/threads is to specify/use the proper nut for the threaded rod material.

After that, it's just checking that the threaded rod tension capacity (with the applicable reduction factors) is greater than the factored tension load, for all the applicable limit states, including fatigue, if the loading is cyclic.