ultimate shear stress

huangyhg

ultimate shear stress
hi all.
when designing carbon steel structures for railcars,
i've often used 0.75 x (ultimate tensile strength) to calculate the ultimate shear stress.
many peple would suggest using 0.58 x ultimate tensile strength.
what do most of you use? can you suggest a reference?
the steel types are commonly a588, a572, a710.
thanks in advance,
tg
the aisc states that the shear yield strength of steel is estimated to be .5 to .625 of its tension yield strength.  they also state that it is often taken to be fy/(square root of 3)= .58fy.
this information is in the commentary section f4 of the asd manual, 9th edition.
i hope this is of help to you.
hi trainguy,
this is a function of h/w and 0.58 is for short and stubby.  you will need to reduce this as h/w and spacing of transverse shear stiffeners change.  0.75 is too high a number by any means.  check the aisc lrfd steel handbook, or arema under steel structures.
regards
vod
the 0.58fy comes from the mohr's circle for shear stress (going back to the strength of materials days). aisc (asd) allowable shear is 0.4fy.
i think 0.75fy is not the proper value because steel will shear well below that.
regards
thank you all for your responses.
in the railway industry, when desiging to yield in shear, we use fsy = 0.58 x fy (yield stress)
when designing for ultimate shear strength, the value of 0.75 x ftu (ultimate tensile strength) is commonly accepted. i've now found the reference - it's the aar (association of american railroads) manual of standards.
cheers,
tg