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Typical shank tension in a tightened bolt

Typical shank tension in a tightened bolt

Typical shank tension in a tightened bolt

(OP)
Hi,

We have a connection with slotted holes - this means that the loading will initially be taken in friction between the plates until the the plates slip and the bolt is loaded in bearing. The bolts are not HSFG (as I understand it the main difference is that HSFG bolts are produced to a higher spec, meaning that they can be preloaded to near enough their full tension capacity?).

I am trying to get a feel for the loading at which slip will occur. The steel designers manual gives a friction force Psl that can be expected per bolt, the formula is:

Psl = 1.1 x ks x mu x P0

where ks is a factor based on the slotted hole direction, mu is the friction coeff between the plates and P0 is a minimum shank tension (preload) in the bolt.

I have no sense for the preload that could be expected by a typical steel fabricator, tensioning to the average man level required with a podger spanner... As they are not HSFG I know it will not be to anything like the same magnitude as a connection designed for this purpose but if you have a grade 8.8. M24 bolt does anyone have a feel for what you could safely assume for P0? 15kN? 7.5kN? Higher?

 

RE: Typical shank tension in a tightened bolt

Essentially zero.  Full effort of a man on an ordinary spud wrench is designated as "Snug Tight" by AISC, and on an M24 [1-inch] bolt it will be less than 1 kip = <1000 psi.  Without a designated minimum assenbly torque, you won't have anything worth quantitfying.
  

RE: Typical shank tension in a tightened bolt

This predicts the wrench is likely 12 to 15 inches long.

I'd predict something in the range of 40 - 80 lb ft of torque.

seems like that would result in 4000 psi or more in a bolt with full sized body.

Like Duwe6 said, there needs to be a specification to begin to be sure of anything.

RE: Typical shank tension in a tightened bolt

(OP)
I recognise you wouldn't want to rely on anything without specifying a minimum torque - I was just trying to get a feel for what a reasonable preload to expect from 'man power' (rather than using any specialist tools) would be... We're having the Contractor run through it with a mock assembly to test the equivalent torque and to test the sliding resistance with load cells so we'll have a pretty good idea of what it is - I was just looking for a number to pop in the calcs as a 'finger in the air' estimate.

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