How to compute Direction Factor (DF) from Modal analysis?
The modal direction factors identify the predominant direction of excitation associated with each of the Modes. The factors are percentages associated with X- and Y- translational and Z-rotational directions. The sum of three values will always added up to 100.
The factor for a particular mode is given by:
where,
Again all summations are overall diaphragms and overall stories.
Sample Example:
