Engineers occasionally specify the use of F3125 Grade A325 heavy hex structural bolts as anchor bolts, but technically they are supposed to be used for structural steel connections only. Part of the problem is that the A325 specification is very specific as to the application and thread length. Because A325 bolts are typically used in structural steel connections, they have very short thread lengths. Often this thread length restriction is too short when the bolts are used as anchor bolts. Since the A325 specification was recategorized under the F3125 specification in 2016, extending the thread length is now allowed provided the heads are marked “A325S” to indicate a nonstandard thread length. Most A325 bolts used as anchor bolts will possess an extended thread length and be marked accordingly.
We occasionally see inquiries for A325 bent anchor bolts or straight anchor rods with anchor plates. Since the A325 specification is restricted to headed bolts only, the F3125 Grade A325 specification suggests moving to either ASTM A449 or A354 Grade BC in these instances. Since both A449 and A354 specifications are designed for general applications (including anchor bolts), engineers should consider these specifications for headed anchor bolts in lieu of F3125 Grade A325 when a similar strength and chemistry is desired. The F1554 specification was developed specifically for anchor bolts and may also be a more appropriate specification to consider when specifying anchor bolts. AISC also discusses which ASTM specifications should be used as anchor bolts.
@lucy76 The ASTM A449 specification reads as follows:
1.2 The fasteners are intended for general engineering use.
This basically means you can use A449 bolts for any application. It is not restricted to a specific type of bolt (heavy hex head) or thread length (as with A325 bolts). Some specifications such as A325 (heavy hex structural bolt), F1554 (anchor bolts), and A193 (high temperature or high pressure service) have very specific uses and configurations as outlined in the ASTM specification.
In reference to this comment, “ASTM A449 is virtually identical in chemistry and strength, but can have longer thread length and is not restricted by the application.” why is it not restricted by the application? Is this due to the longer thread length? Thanks for any info you can offer!
what is the tensile strength difference for A325 and A36 anchor bolts. thank you
In my opinion for anchor bolt we should restrict ourselves upto either ASTM A 307 or A36. Philosophy for this is bolt failure should occur prior to concret failure. Higher strength bolt will require quite stringent tensile requirement of concrete in effective concret cone (resistant against pull out, cone) which depends upon embedment depth, edge distance, center to center of bolt.
What is the advantage of ASTM A449 over ASTM F1554, pertaining to the above discussion?
@Dave ASTM A449 does not have any advantages or disadvantages versus F1554 as an anchor bolt specification….it simply has different characteristics. There are three grades of F1554 anchor bolts. Grade 36 is manufactured from mild steel and has a minimum yield strength of 36ksi. Grade 55 is a modified mild steel that has a 55 ksi minimum yield requirement. Grade 105 is a medium carbon alloy (often 4140) that undergoes a heat treating process and requires a minimum yield strength of 105 ksi.
Whereas F1554 is applicable only to anchor bolts, A449 is not specific to anchor bolts but can certainly be used as an anchor bolt specification (whereas A325 cannot). A449 differs in chemistry and strength from any of the F1554 grades. A449 bolts are manufactured from a medium carbon steel (often 1045) and heat treated to develop its strength characteristics which lie between F1554 Grade 55 and F1554 Grade 105. A comparison of the specifications can be found on our bolt strength by grade chart.
Therefore, depending on what combination of strength and ductility an engineer is looking for out of an anchor bolt for a specific application, any of the three grade of F1554 or A449 can be specified.