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RE: Dynamic analysis

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Shamini,

	If you modeled a structure with a weak part or weak elements then vibration
of those elements occur in the modes prior to the mode of global vibration
of the structure. This is also a good check to detect these minor modes to
find these elements. Usually you should correct these parts of structure to
have the global vibration of structure in successive modes.

Regards,
A. Karimzadegan
M.S. C.E.
PIDEC
Shiraz - Iran
T : +98-711-2270120
F : +98-711-2299412
e-mail : karimzadegan(--nospam--at)pidec.com

-----Original Message-----
From: Shamini Wijay [mailto:swijay(--nospam--at)fdgoc.com]
Sent: Monday, December 20, 2004 7:26 PM
To: seaint(--nospam--at)seaint.org
Subject: Dynamic analysis


I have a 7 story parking structure with 2 levels of basements. I am using
Etabs to model the structure and carried out a dynamic analysis using Ritz
vector. Every frame line is a special moment resisting frames. Therefore I
have a huge redundancy. I am getting 90% mass participation at mode 20. Is
this valid? The plan checkers are saying, I should get 90% mass
participation at mode 6, 7.

Is there anything I could refer to for this?

Happy Holidays!

Thank you.

Shamini


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