Gross vs Root area of bolts

[Polecat]

How did AISC justify using the gross area (Ab) for bolts in tension instead of the root area of the threads?
Did they simply reduce the allowable stresses by a ratio of the root/gross areas?

Polecat

http://www.spiraleng.com

 

[woodman88]

Per the pdf at

http://www.boltcouncil.org/files/2004RCSCSpecification.pdf

on page 31

"The tensile strength of a high-strength bolt is the product of its ultimate tensile strength (per unit area) and some area through the threaded portion. This area, called the tensile stress area, is a derived quantity that is a function of the relative thread size and pitch. For the usual sizes of structural bolts, it is about 75 percent of the nominal cross-sectional area of the bolt. Hence, the nominal tensile strengths per unit area given in Table 5.1 are 0.75 times the tensile strength of the bolt material. According to Equation 5.1, the nominal area of the bolt is then used to calculate the design strength in tension. The nominal strengths so-calculated are intended to form the basis for comparison with the externally applied bolt tension plus any additional tension that results from prying action that is produced by deformation of the connected elements."

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[WillisV]

Yes.

 

[JLNJ]

Sometimes you are required to use the root area. Anchor bolts and fatigue calculations come to mind.