For a typical line stop in one uninsulated hot piping, what could be the allowable shear stress for the following parameters:

applicable code - B 31.3
structural steel for line stop - A 36M
pipe flexibility temperature - 300 C

As the structural steel for line stop is placed below shoe, can we take temperature as ambient for this while considering the allowable stress in shear (0.8 times that in tension as per B 31.3) ?

Is this approach right or can we take AISC stress allowable at ambient temperature (say 0.4 * Yield stress) ?

regards,

sam