Specification of Different Bolt Grades

[JohnnnyBoy]

For general work in Canada.

It seems like contractors or certain clients like certain types and grades of bolts that are sometimes different that typical specified.

Currently our client wants to use a Class 8.8 Steel Hex Bolt that meats SAE J1199. The project itself is a platform that would be designed using S16-19 - Design of Steel Structures. Within S16-19, connection design solely seems to incorporate A325, A325M, F1852, A490, A490M, F2280, A307. I do think its funny that a Canadian code (metric) uses mostly ASTM or imperial standards other than the metric equivalents of A325M and A490M, mostly since we are so closely ties to the US.

My overall question is when can we differ from what the code allows, and would the same formulas apply to different grades of steel not shown within the standard. Ductility, bearing, tensile, etc would be slightly different for each type of fastener. Engineering judgment is an obvious answer, but is there any sort of document that speaks to this a little bit. I see it happening more often now with issues with supply.

 

[dik]

Get the EOR to approve ASTM F3125, GRADE A325 bolts and imperial size M19 bolts are less costly than M20.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[JohnnnyBoy]

I guess my question was more so as the EOR is it typical to approve bolt grades not mentioned within the design code. A simple check of shear strength, tension, etc. can easily be done using S16 but S16 was not meant to be used for grade of bolts outside of what is mentioned within the code itself.

Seems like I have two options, take a hard stance against the use of any other grade of steel, or use the code and check using the tensile strength of the steel that is wanted to use. Wondering if there is some additional risk due to the change in ductility of the bolts.

 

[skeletron]

1. I don't think it is common for a steel structure to have anything but A325 (ASTM F3125) or A490. I have seen the SAE request for anchor bolts, but that has only been on wood frame structures and my understanding that it is a result of availability.

2. Because so much of S16 has developed the provisions based on testing and reliability indices, I would be hesitant to approve anything other than the ASTM F3125 bolts. You could potentially compare ASTM F3125 and SAE J1199, then make your own conclusions. It may certainly work based on the fundamental equations, but how much gravy are you putting on top to cover up the difference in bolts? Does the phi factor still apply? Do the additional coefficients still apply?

 

[dik]

I often encounter them spec'd in lieu of A325/A490, maybe a couple of times a month... My SMath program calculates the shear both snug tight and slip critical, tension and bearing capacity and if A325/A490s work, then add a note for the EOR to confirm the use of them. If you are the EOR then you should be able to specify what you want to see used.

The bolt research council has a publication that stipulates tightening of A325/A490 bolts that may not be applicable to other grades.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[WinelandV]

The big feature of A325/A490 is that (if I'm remembering correctly) head on the bolt is bigger than the corresponding bolt head on ASME bolts.

For shear only connections, it's likely an ok substitution. For tension applications, I would not substitute, as the A325/A490 bolt capacities preclude any head pull-through failures (due to the larger bearing area).

 

[JohnnnyBoy]

Appreciate the comments everyone. Luckily this design is a shear connection only and not even at 50% capacity so lots of gravy.

Interesting comment on the bolt pull-through failure and will have to keep that in mind on future projects when the bolts are in tension.