matle
Structural
- Jan 11, 2012
- 7
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?
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?
