Pin Hole Tolerances

[gvot]

When integrating pin holes for tension eyebars or standard clevis connections what is the accepted tolerance for the hole placed in the structural. Further what is the tolerance on the roundness for the holes? AISC D6.2 states pin holes shall not be more than 1/32” larger than the pin, however, the code doesn’t appear to address the tolerance of the hole.

 

[dhengr]

Gvot:
The 1/32” dia. difference relates to the fit of the pin within the pin holes in the pls., and further relates to the pin bearing stresses in the pin pl. That dia. difference is an important variable in the determination of the bearing conditions and stresses btwn. the pin and the hole in the pl. Look up Hertz bearing stresses in a good Strength of Materials or Theory of Elasticity textbook. There certainly will be an eyebar length tolerance on the pin hole centers someplace on the plans or specs. I don’t have some std. value off the top of my head, it will be somewhat dependent on the size and length of the eyebars. Often, the bars will be match bored in sets to some machine shop tolerances. Eyebars within a particular set should be fairly closely matched for good stress distribution, fit-up and performance. Different sets of bars can have a slightly less critical length tolerance and the system will still work o.k.

 

[bones206]

My understanding is that if you are designing a "pin-connected member", you only have to use the pin diameter + 1/32" (max) when "the pin is expected to provide for relative movement between connected parts while under full load". Otherwise I think you are free to design the pin hole in the convention Chapter J methodology with your chosen hole size. Please correct me if I am misunderstanding the code [AISC 360-16, D5.2(b)] on this.

 

[hokie66]

Just be careful with the geometry. Had a cantilevered awning section with some pin connected bracing to the supporting column. The fabricator decided to take a bit of liberty with the hole size. When erected, the awning noticeably sagged. Not because the cantilevered beams or the column were bending too much, but just because of slop in the pin holes. A little bit of movement back at the start magnifies at the end, and in this case was a visual problem.