The code requires "scalar combination" as follows:

302.3.6 Limits of Calculated Stresses Due to Occasional
Loads
(a) Operation. The sum of the longitudinal stresses,
SL, due to sustained loads, such as pressure and weight,
and of the stresses produced by occasional loads, such
as wind or earthquake, may be as much as 1.33 times
the basic allowable stress given in Appendix A.

Now we do some magic and delete some words:

302.3.6 Limits of Calculated Stresses Due to Occasional
Loads
(a) ........... The sum of the ..... stresses,
...........,AND of the stresses.......

hence "scalar combination"

Best regards,