Intermediate Stiffener Welds

[penpal97]

I am reading "Structural Steel Design: LRFD 3rd Ed" by A. Williams. For design of Plate Girders, Ch 8.4 says intermediate stiffeners (when required, with or without tension field action) must be connected to webs to resist shear given by
f_vs = 1.67h(Fy/340)^1.5

Could someone help tell me where this equation comes from? Or help me understand how it was derived (if not a reference)?

 

[271828]

According to Salmon & Johnson, it comes from the Basler ASCE Journal of the Structural Division paper, 1961, called "Strength of Plate Girders in Shear."

S&J says that this weld is designed to transfer the required stiffener force over 1/3 of the girder height. They say it's a requirement when TFA is used. It's Eq. 11.11.20 and 21 (with an ASD factor of safety) in the 1990 S&J.

 

[penpal97]

thank you. does that mean that this is equation is from a paper, not found in the AISC specifications?