Allowable bending stress of coped beam seat

[Qrs]

I was reviewing how to designed a coped beam seat for a beam and was following the example in the “designing with vulcraft” 2nd edition manual.

When determining the bending capacity of the bottom plate (of the seat), they using an allowable stress of 0.75Fy.
When determining the bending capacity of the built up cantilever section, they use an allowable stress of 0.6Fy.

I would expect it to be 0.6Fy for both (Fy/1.67). Why do they use 0.75Fy at all? (See attached.)

 

[msquared48]

Compact Section?

Mike McCann, PE, SE (WA)

 

[neffers]

Plates in weak axis bending had an allowable stress = .75*Fy according to the 9th Edition ASD AISC Manual.

 

[KootK]

One could use Zx for the plate design could the not?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[Qrs]

Gotcha. Thanks everyone!