Seismic analysis EC8

[Structural Shaft]

I'm working one my first fullsize project in RSAP(Robot Structural Analysis Proffesional) 2011. I have finished the model but, meshing and vertification goes smooth but here is also were the first problems occur. The differences in the stiffness of the materials and of course eccentric arcitchture makes the modal analysis though. The model doesn't reach 90% participation of mass for each of the horizontal direction before after 300 modes.

Any advise would be highly appreciated.

[costasm27]

Thin and slender sections are prone to vibrations with a low mass participation. Try to remove any unnecessary slender members in order to reduce the number of modal cases!

[Structural Shaft]

Do I have to introduce reinfocement in the concrete before doing the seismic analysis?

[costasm27]

The common practice especially for new buildings is to perform the analysis and then design the reinforcement that satisfies the results obtained. If you want to do a performance based design approach then yes. This is the way to follow if you wish to check the limits of your structure. Not usual in common practice.

[Structural Shaft]

Excellent thank you so much for your valuable help. Is the same practice used toward the supports? For mye initial calculations I just selected ridig supports.