Period of different directions

[julyan]

Hello everyone,

Conciser we want to model a 3D frame with different type of lateral-load-resisting structural system in different directions (for example moment-resistant frame in X-dir and shear wall with frame in Y-dir).
1.How can we distinguish the principal period of frame in different directions?
2.How can we distinguish another periods of frame in different directions?

Best,

[fmk]

look at the eigenvectors at the nodes.