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Bolts in tension + a load
3

Bolts in tension + a load

Bolts in tension + a load

(OP)
Hypothetical

If I have an M10 bolt holding a plate with a hook to the roof and I have torqued it up correctly and it has 3,300kgs of clamp. Then I attach a 1,000kgs weight on the hook which is a straight line pull. Is the bolt now over stressed resisting a load of 4,300kgs?

Deleted segment on actuals

RE: Bolts in tension + a load

More info needed.

1 - The description of the 1000 kg weight and 4,300kg load has me scratching my head.
As do the descriptions of "an M10 bolt" and "only 4 X M10 bolts ."

2 - The details of the hook and whatever it is bolted to can induce big bending and prying loads greater than the simplfied straight line pull.

Thoughtful pictures are our only hope now.

RE: Bolts in tension + a load

(OP)
The bolt in the ceiling fixes vertically up from below. It is fixed through a plate. The bolt has clamped the plate to the ceiling. The ceiling is at a rightangle to gravity. It has been tightened such that it has clamped the plate to the ceiling with 3,300kgs (it's SWL) in tension. Attached to the plate is a hook. It is designed such that any weight on the hook will apply a force exactly collinear to the centre line of the bolt.

If a weight of 1000kgs is placed on the hook has the bolt been overstressed.

RE: Bolts in tension + a load

(OP)
Got it, thanks

RE: Bolts in tension + a load

not sure about the points being made.

when you preload a bolt, you set up a compression field in the material being clamped.

when you apply an external load to the bolt, the bolt reacts only some of this external load, and the clamped up material the rest.
look into "bolt loading diagrams", there's a lot of material out there on this topic.

The simple assumption is that that the bolt reacts the preload until the external load cause gapping (equals the preload) then the bolt reacts the applied load.
The "truth" is more complicated. If the bolt reacted 1/2 the applied load, then the load is higher than preload, until the joint gaps (at 2*preload).

If this was already clear, sorry about the "expert-splaining".

another day in paradise, or is paradise one day closer ?

RE: Bolts in tension + a load

In the words of my favorite college professor: "A bolt is weak. A bolted connection is strong."

RE: Bolts in tension + a load

(OP)
rb1956... "If the bolt reacted 1/2 the applied load, then the load is higher than preload, until the joint gaps (at 2*preload)".


Would this only be true if the bolt and the bolted material were of equal strength ?

RE: Bolts in tension + a load

Hi TmcRally

Have a look at the link below, the joint stiffness is usually much stiffer than the bolt and therefore carries the lions share of the applied load

https://www.tribology-abc.com/calculators/e3_6h.ht...

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

RE: Bolts in tension + a load

"If the bolt reacted 1/2 the applied load, then the load is higher than preload, until the joint gaps (at 2*preload)".

this was meant only as an example. The calculation of clamp up load is quite complex and not directly related to bolt or clamped material "strength".

another day in paradise, or is paradise one day closer ?

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