AISC 13th Manual, Section J3.7 Question

[swearingen]

In section J3.7 of the 13th Edition AISC Manual, after defining the variables used in the equations, the Manual states: "The available shear stress of the fastener shall equal or exceed the required shear strength per unit area, fv." I thought the purpose of the equation was to find the available tensile stress left in the bolt after the effects of shear stress have been accounted for, especially since fv appears in the equation. Should the statement say "available tensile stress" or am I missing something?

 

[Bagman2524]

Looks like its' saying that after the tensile stress has been checked, you still have to check the shear to verify its' below the shear allowable.

 

[chichuck]

Bagman2524 has it right. The available tensile strength in Eq. J3-2 is based on the nominal tensile stress (allowed) for the bolt that is modified (ie. reduced) to that for combined tension and shear. Recall in the old 9th edition ASD, for example that Ft for a bolt is from Table J3.3:

Ft = sqrt[ (44)^2 - 3.75*fv^2) for A325 bolts, bearing connection with threads included in shear plane. fv is the applied shear stress. This is a tension/shear interaction valuke.

After you check that "combined stress value" you must also verify that applied shear, fv is less than allowable shear Fv for the bolt. The new code is written in terms of available stresses but this is still the same concept. I believe that the values are unchanged from the earlier code as well.


regards,


chichuck