Bolt Bearing in a Shear Connection 5

[dik]

The Canadian steel code S16 allows for bearing equal to:

3 x ϕbr x n x t x db x Fu

where ϕbr is 0.8
n is number of fasteners
t is the thickness
db is the bolt dia
Fu is the UTS

I couldn't find anywhere that clarifies that this is the bearing material and not the bolt, and why would the value be so relatively high? I assume the AISC has something similar.


Dik

 

[r13]

Check the Fu, I believe it refers to the base metal, not the bolt.

 

[dik]

Thanks... Fu is also referenced with bolt strength, too... the reason for the conclusion. That was my original understanding... I was just wondering.


Dik

 

[r13]

AISC has 3 equations for bearing strength of bolt connection, and "Fu = minimum tensile strength of the connected material, ksi"

 

[dik]

Thanks...


Dik

 

[r13]

You are welcome.

 

[Agent666]

Dik, as to the why. The following excerpt explains the logic. Not Canadian specifically, but similar logic would have applied in determining your coefficient of 3.

 

[dik]

Thanks, Agent... I guess the 3 is not excessive.

Dik

 

[Agent666]

Yeah, I guess if you Google images of bearing failures you'll see there is a lot of deformation occuring to get to that limit state. The piling up of the material referenced is expected. So it is never intended to be an elastic (recoverable) phenomenon.

If you're after a "more" elastic approach I believe following the advice for 'pins' in any code is more appropriate.

For example see below from NZ code, Canada likely has similar provisions for pins. You'll note it is based on yield strength and lower factor overall.

 

[dhengr]

Agent666:
RE: your last two posts, very nicely done and explained. That’s about what I remember as an explanation and the way of dealing with bolts and pins, although I don’t have copies of those two stds. which you show copies of.

 

[dik]

Thanks, again Agent... much appreciated and the explanation was great. Is that an AISC commentary?


Dik

 

[BAretired]

I think it is from the NZ code, dik.

BA

 

[Agent666]

No problem . The screenshots are specifically from the New Zealand Steel code, NZS3404:1997.

The concepts involved in international codes are all based on similar research, whether it's a 3 or 3.2 factor the concept, reasoning and intent is similar.

The reference 9.12 mentioned in the first post/first screenshot is the following publication, which goes through it in a lot more detail and compares various international codes of the time and research on the subject (late 1970's) from an Australasian perspective.

 

[dik]

Thanks Bart...and Agent


Dik

 

[jayrod12]

Dik,

Screenshot of CSAS16-14

 

[dik]

Thanks Jayrod... had that... but thought the values were too high and wasn't sure if they were referring to the Fu of the bolt, or the base metal. For screenshots, do you use <Win><Shift><S>?


Dik

 

[r13]

<Shift><PrtSC> on my keyboard, then paste onto Paint for crop and edit.

 

[BAretired]

dik,

I use <win><shift><S> to get the image on the clipboard, but can't paste directly to the E-T file. Must create a pgn or jpg file and use the image tool to get it on E-T.

BA

 

[jayrod12]

I do use win shift S.

Then click the image button and click within the area that says drop file here. then I ctrl-v. all done.

Isn't the Fu of the bolt material generally higher? Except for A307 which are only allowed for wood connections and anchor bolts.

 

[BAretired]

How about that...it works.

BA