Anchor Bolts

[joemarch]

Typically I use F1554 anchor bolts. I have a case where I need to develop the capacity of A325 bolts in a cage of steel. Is it possible to get headed anchor bolts 30" long with a capacity equal to A325's. Thanks for your help.

 

[JStephen]

Seems like I have seen A193/4 used for higher strength bolts. Consider a stud threaded on both ends with a nut in lieu of a headed bolt.

 

[mrengineer]

For "high strength" anchor rods we typically specify ASTM F1554, Grade 105, or ASTM A193, Grade B7, with heavy hex nut at bottom of rod.

 

[LPPE]

F1554 comes in different grades. Perhaps try grade 55 or grade 105?

 

[joemarch]

sounds good. thanks all!

 

[WillisV]

ASTM F1554 GR105 and ASTM 103 Grade B7 are equivalent as far as load calculations (same ultimate tensile strength and similiar elongations). Be careful specifying F1554 GR55 bolts as these are classified as brittle rather than ductile according to the criteria set forth in ACI Appendix D and you take a strength penalty. Normally I skip from GR36 to GR105.

 

[LPPE]

According to AISC, F1554 gr. 55 is the most commonly specified anchor rod. And they prefer to call them anchor rods, not anchor bolts. Check out Modern Steel Construction, March 1999 "Are You Properly Specifying Materials?"

 

[WillisV]

LPPE - my comment regarding GR55 did not have anything to do with if they are common or not - just that I normally specify F1554 GR36 or GR105 because the actual strength gain from GR36 to GR55 is miniscule using IBC 2000 which is the governing code in my area.

Reason being, according to IBC 2000 Sec. 1913.2.1 Definitions, an element must have a tensile test elongation of at least 14 percent and reduction in area of at least 40 percent to meet a "Ductile Steel Element" classification. GR36 and GR105 meet these requirements however GR55 has a reduction in area of only 30%.

Therefore it is classified as a brittle element and you get hit with a phi reduction from 0.90 for ductile to 0.75 for brittle steel strength (1913.4.4). Also note that the steel strength is based on ultimate not yield stress. Allowable ultimate stress is 58 for GR36 and 75 for GR55. So going from a GR36 to a GR55 you only gain [(0.75/0.9)(75)]/58 = 1.077 = about 8% strength gain. So either 1. Use a slightly larger GR36 or 2. Jump up to GR105.

Note that in IBC 2003 which Ref. ACI-02 Appendix D the requirements for ductility have been reduced to 30% and therefore GR55 would be considered ductile and the above does not apply.

 

[LPPE]

WillisV - My apologies, I did not mean to suggest you were incorrect in any way. My intent was only to add another $0.02 to the discussion and present AISC's view of anchor rods. I agree with what you say above.