Participating mass ratio

[babayaga]

hi,. just learning ETABS.
my problem is that my 2-story design do not get 80 or 90% of the participating mass ratio
I already run the analysis and checked the modal, i only get 72%
what maybe wrong with my design.

i will attach my design if ever you want to check.. thank you.

 

[chekre]

Increase ur eigenvectors modes or use the Ritz ones.

 

[JasonMcKee71]

Ritzy method would definitely help.

Jason McKee
proud R&D Manager of
Cross Section Analysis & Design
Software for the structural design of cross sections
Moment Curvature Analysis
Interaction Diagrams
Reifnorcement Design etc.

 

[wannabeSE]

I did not look at the model (I am at home and ETABS is at work). Have you looked at the mode shape and deflected animations to see if they are reasonable. Sometimes this will reveal an element flopping.