I am not familiar with B31.8, but I'll presume its like B31.3 in this instance to maybe give you something to check.
B31.3 code stresses are in the sustained and expansion cases. Support loads are in the operating cases, generally speaking. So the code compliance report from CAESAR II does not show allowable stresses for operating cases because the code does not define an allowable stress for that case. See the below picture from a generic CAESAR II code compliance output for B31.3. Note that there are no allowable stresses in the operating case.