COMPRESS horizontal vessel anchor bolts

[KN25]

What value should be used as an input for "allowable shear stress" for anchor bolts when designing a saddle for horizontal vessel in compress?
I am using SA-193 B7.
The default values is 15000 psi.
I believe this value is for Sa-307, and it is allowable tensile stress.
What is the allowable shear stress, and how it is calculated?
Is there any rule per ASME VIII DIV 1 for calculating allowable stresses for bolts?
Thanks for your answers !!

 

[MikeG7]

I would have just used 0.5 x tensile as a rule of thumb. Perhaps it is prescribed in ASME what to use?