Why don’t the values reported for the building story shear correspond to the values reported for the change in story shear?
The combination of modal results can affect interpretation of the results, especially building story shear and change in story shear. The program calculates a total story shear and a change in shear for each mode in the analysis. The results are each combined using either the SRSS or CQC combination. As a result, the reported change in shear is not linearly related to the reported building shear. For the same reason, the reported building story shears should not be expected to match the sum of the reported frame story shears. If one is trying to determine equivalent static forces to apply to the diaphragms to match the total base shear, the reported shear from one level should be manually subtracted from the shear reported in the adjacent level rather than using the change in shear values reported in the Building Story Shear Report.
