1- It is expected that the analysis of entire structure gives more accuracy.
The best reason is considering interaction effects of strcutural parts in
analysis. Although some codes permit ignoring this interaction for rigid
base part, but in my opinion when a specific structure needs dynamic
analysis for irregularities, the interaction effects become important.
2- As far as my experience in using finite element models, to get better
accuracy, the way that below shear walls models, will affect the result.
It's mainly because unreal stress concentration in the contact nodes of
shear wall and frame member elements caused by numerical analysis method.
Hope that it helps,
Fariborz Tehrani, Phone: (310)509-8826
Civil Engineer Fax: (530)481-9532
BSCE, MSCE, PE Voice Mail: (877)743-6206
From: "Yousefi, Ben" <Ben.Yousefi(--nospam--at)ci.sj.ca.us>
To: "'SEAINT(--nospam--at)SEAINT.ORG'" <SEAINT(--nospam--at)SEAINT.ORG>
Subject: Dynamic Analysis Question
Date: Thu, 13 Jan 2000 14:40:53 -0800
For those of you who are dynamic analysis experts, or have had substantial
experience in this field, here is a question:
We have a structure that is comprised of an irregular midrise tower (say 15
stories) utilizing moment frames located on top of a low rise,
rigid base (concrete shear walls). Originally the building was dynamically
analyzed as two separate sections. In the first run the tower was assumed
be a separate building located at grade and in the second run the forces
from the tower were applied at the top of the base and then analyzed. This
appeared to be crude approximation of the building behavior. So another run
was performed modeling the building as a whole.
As one might expect when the building is analyzed as whole, a substantial
portion of the forces induced by the base is getting dumped into the tower
and penalizing the tower frames.
The question is which one is more realistic? Is there a middle ground or
Thanks in advance
Ben Yousefi, SE
San Jose, CA