The sum of the modal weights for the computed modes may be compared to the total weight of the structure (that has not been lumped at supports). The difference is the amount of mass missing from a dynamic, base excitation, modal response analysis. If too much is missing, then rerun the eigensolution asking for a greater number of modes or read about how to employ the Missing Mass Correction method.
The Missing Mass Correction Method is most important for adequately capturing the higher-frequency response near supports.
The Missing Mass Correction Method is most important for adequately capturing the higher-frequency response near supports.