Insufficient number of modes

For vibration mode proficiency check , the condition given in TBDY 2018 Article is applied. - In modal calculation methods, sufficient number of vibration modes to be taken into account , YM, 

(a) According to Annex 4B , the base shear force calculated for each mode in earthquake directions (X) and (Y) shall be determined according to the rule that the sum of the modal effective masses is not less than 95% of the total building mass .  

The mode insufficient message is given when 95% is not achieved.

Solution :

  • Increase the "number of targeted modes" value that can be entered in Modal E1, E2, E3, E4 and if any, Modal BE1, BE2, BE3, B4 uploads listed under Analysis / Modal Analysis / Modal analysis from the structure tree and repeat the analysis.


Note: Modal E2, E3, E4 refresh automatically when changes are made to Modal E1. Similarly, when changes are made to Modal BE1, BE2, BE3, B4 are automatically renewed.

  • Ritz vectors method can be used instead of Eigen.

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