RCSC Specification Vs AISC

[ChrisNYCEng]

In working through some practice problems for the SE exam, I came across a difference in how to calculate the available tensile capacity of a bolt subjects to shear and tension. RSCS would be per equation 5.2 and rearranging to solve for Max tensions allowed would yield Tu < Phi*Rnt*SQRT(1-(Vu/(Phi*Rnv))^2)

This is different than in AISC spec page 16.1-109 where F'nt = 1.3Fnt-Fnt*fv/(phi*Fnv) <= Fnt.

Are both equations ok to use even though they yield quite different results? I am seeing a difference of around 20% for a 1" Dia A325N bolt with about 22.5k of shear.

 

[wannabeSE]

AISC 360-05 commentary for J3.7 provides an explanation. It says: "generally, use of the elliptical relationship is acceptable" Figure C-J3.1 graphs the solution to both equations and shows the difference.

 

[ajh1]

The next edition of the RCSC Specification will be using the identical formulas to AISC.

 

[Hokie93]

In cases such as this, it is best to use the AISC Specification equation since the AISC Specification is the document legally adopted by the building code (by IBC 2012, for example). The RCSC Specification is not part of the building code but, rather, provides much of the basis for the bolt-related provisions in Chapter J of the AISC Specification.

 

[ChrisNYCEng]

Thanks for the help guys.