Are Grade 5 bolts as reliable as A325 2

[RARWOOD]

As a structural engineer with a background in steel building design I am very familair with A325 bolts but not SAE Grade 5. It is my understanding that the A325 specifications are a little more restrictive than the Grade 5 specifications.

For the applications I am looking at the connections are almost always controlled by shear. In the design I assume a bearing connection with the threads included in the shear plane. There are now code or specification requirements that would require or prohibit the use of either grade.

I know that the design properties of A325 and Grade 5 bolts are the same. So on the surface it appears, that if I have a single shear connection with a load of 30 kips, I could use either a 1 3/8" diam. A325 or Grade 5 bolt.

As a structural engineer I feel more comfortable using a A325 bolt. A325 bolts however are a lot more expensive than Grade 5. So I am wondering are there good reasons I would want to stay with A325 bolts or am I just as well off using Grade 5 bolts.

 

[LEEMARVIN]

Bump ... Does anyone have any thoughts? I actually was having this conversation with a coworker today!!

Any help is very much appreciated.

 

[minerk]

According to Machinery's Handbook SAE Grade 5 covers bolts between 1/4" and 1". Larger bolts with the Grade 5 marking are actually ASTM A449.

 

[GBor]

Well, I have to come from the other side and say that I'm not that familiar with A325 bolts. I'm assuming A325 is corrosion resistant. Grade 5 are carbon steel...unless you coat them with polysulfide or some other moisture isolator, you will have rust and have to consider it for design purposes.

My experience is more with marine-based structures, so not sure how this translates to land-based structure.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group
Magnitude The Finite Element Analysis Magazine for the Engineering Community

 

[LEEMARVIN]

How does the heavy hex head of the A325 come into play?

If you use the gr 5 you lose the heavy hex head and still have to use a A194 2H Heavy Hex nut.

And if the larger SAE gr 5 is A449 then that is comparable to the ASTM A490 which have higher values than the A325.

So are the specs simply more uniform with A325's than gr 5's??

And I am very interested in how the heavy hex head comes into play.

 

[crossframe]

This might help:

From AISC’s publication, A Guide to Engineering and Quality Criteria: Common Questions Answered:

Question 6.2.5: Is it acceptable to substitute SAE J429 grades 5 and 8 bolts for ASTM A325 and A490 bolts, respectively?

Answer: No. The strength properties of SAE J429 grade 5 bolts and ASTM A325 bolts are identical; likewise, SAE J429 grade 8 bolts are the strength equivalent of ASTM A490 bolts. These material specifications differ, however, in that ASTM A325 and A490 specify thread length and head size, whereas SAE J429 does not. Additionally, quality assurance and inspection requirements for ASTM A325 and A490 bolts are more stringent.

Since AISC and RCSC specifications call for pretensioned installation for your application (which involves fatigue), I would question whether the SAE fasteners that were installed were properly installed. Also, I’d question if the head size, threading and quality assurance were adequate for the application. Usually, the request to substitute an SAE fastener for A325 or A490 comes because SAE’s are cheaper. Perhaps that gives you the answer right there.

 

[minerk]

Grade 5 bolts from a reputable source are certainly reliable. If there is no code or other specific requirement to use A325 then there is no reason that SAE Grade 5 bolts couldn't be used. If anyone has to replace these bolts in the future you can bet they'll probably do it with Grade 5.

I also read the comment from the AISC site, and the statement that J429 doesn't specify head size is a bit misleading. J429 may not specify it, but there certainly is a "standard" head size for any given size Grade 5 bolt.

The biggest issue I find with any bolted connection is getting the "hands-on" guys to install and tension the fasteners properly.

 

[LEEMARVIN]

Thank you Crossframe!! That definetly gives me a goood answer to my question.

To correct myself - in an earlier post I wrote A449 is = to A490. It is not A449 is an = to A325 and A354BD is = to A490. Both A449 and A354BD are common stud specs.

 

[civilperson]

Steel structures built to AISC must use A325 or A490 bolts.

 

[RARWOOD]

civilperson

What do you do if your connection requires 2" diameter bolts? In addition I believe the AISC Ninth Edition allowed the use of A307 bolts.

I want to thank every one for their input!!!

In the past when designing steel structures using the AISC specifications, I have always used A325 or A490 bolts.

My application is for use of bolts as part of a timber truss designing following AITC and NDS specifications. The grade 5 bolts would be used only in steel to steel connections. In most of the applications I would use grade 5 bolts are ones where the shop is instructed to install the bolts snug tight. All the other bolts used in the truss would be A307.

 

[GBor]

RARSWC,

For those posts that were particularly helpful, click on the "Thank _______ for this valuable post" and then confirm. It will place the star beside their handle and is a way of giving them a vote for "Tipmaster of the week". Most of us will never respond to enough posts to see that illustrious title, but some of these other guys deserve it for their contibutions.