Bolt Strength

[JSPILLER3]

Does anyone know why, the tabulated values for the shear strength and to a lesser extent the tensile strength of bolts has changed so much. I have been comparing the 9th, 13th and 14th addition of the AISC steel manual and for example, A307 bolt available shear strength(kips), single shear, 9th add - 4.4, 13th - 5.3, 14th - 5.97. This seems to be a large change and I cannot account for it, other than technology is better and a larger allowable is now permitted. Are there other considerations being taken into account? Thanks for your help and time.

 

[frv]

That is the "major" change to the 14th Ed. There is a note about this in this month's Modern Steel Construction (you can view it for free online).

Brief summary: there used to be a 20% reduction to account for uneven distribution of load in connections up to 50 in. in length. The reduction is now 10% for connections up to 38 in. in length.