The combination method for the default ASME B31.1 occasional code combinations is absolute sum. Per ASME B31.1 para 104.8.4(b), if the method of analysis for occasional loads is such that only the force and moment magnitudes without relative algebraic signs are obtained, the most conservative (absolute sum) combination of the signed and unsigned forces and moments shall be used.

For a nonlinear analysis in which the earthquake loads are applied in all combinations of direction and signs, the calculated forces and moments retain the correct algebraic signs. The combination method "absolute sum" is then overly conservative in some cases. The combination method "sum" would be more appropriate in this case.

I propose an option be added to the Combinations dialog to change the combination method for default occasional code combinations from "absolute sum" to "sum".