modal participating mass ratio 2

[ingenierobou]

Hello

I am working on a two-story steel building, and after 50 modes the participating mass ratio in Y-direction barely passes 75%. What can I do to increase the mass?

Best regards.

 

[ingenierobou]

I would like to know if for a simple two-story building, 120 modes to achieve 99% of the modal participating mass ratio is not too much? The building has about 120 small cantilever beams in the roof level.
regards

 

[structSU10]

the modal mass participation depends on the number of degrees of freedom. the more degrees of freedom, the more frequencies, and likely the more modes are required to get the percentage of mass participation you need. 120 sounds like alot, but if there a thousands of degrees of freedom, maybe it is reasonable.

 

[johnbridge231]

you may want to try the Ritz vector to overcome this issue.

Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis

http://www.engissol.com/cross-section-analysis-design.html