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UBC 97 anchor bolt design

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Regarding design of anchorage to concrete, from UBC 97 Section 1923.3 (strength design):
 
When checking the steel strength, say for an A307 anchor bolt, Pss = 0.9*Ab*fut; fut is the minimum specified tensile strength, given as 60,000 psi for A307 bolts.  Ab is the anchor area.  The use of the tensile strength, rather than the nominal strength of 45,000 as given in LRFD Table J3.2, would suggest that the net tensile area should be used for Ab.  The 1997 NEHRP, Section 9.2.4.1, though, uses the same bolt strength equation with Ab defined as the 'area of the shank of the bolt or stud'.
 
Knowing that normal bolt allowables take into account the reduction in tensile area and allow the use of nominal areas, is this a different situation in which the tensile area must be used?
 
Thanks for any insights on this.
 
Jim Carey, P.E.