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RE: Dynamic Analysis Question

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Thank you everyone for your input.

	Now let me provide you some additional relevant information, or
maybe the second part of the question. The dynamic analysis had revealed
that the dominant modes for upper tower and lower podium were dramatically
different. Assume the decision is made to use the distribution of forces per
the model of building as a whole. When it comes time to scale the forces
back to the code level forces what do you scale it to? And would you scale
the forces for each section separately? According to which period?"

Thanks again

Ben Yousefi, SE
San Jose, CA

	-----Original Message-----
	From:	Walter Sawruk [SMTP:sawruk(--nospam--at)]
	Sent:	Thursday, January 13, 2000 3:17 PM
	To:	seaint(--nospam--at)
	Subject:	Re: Dynamic Analysis Question


	In general, I think the coupled analysis would be the more
	However, there are many potentail pitfalls which could have
	extra conservatism into the combined model (e.g., eccentricities)
and the
	solution details (e.g., modal combination method).  Without knowing
	specific details, no one can say for sure which one of your results
is the
	most realistic.

	Walter Sawruk
	EQE International, Inc.
	Shillington, PA
	email: ws(--nospam--at)

	At 02:40 PM 13-01-2000 -0800, you wrote:
	>For those of you who are dynamic analysis experts, or have had
	>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
	>analyzed as two separate sections. In the first run the tower was
assumed to
	>be a separate building located at grade and in the second run the
	>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
	>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
	>better alternative?
	>Thanks in advance
	>Ben Yousefi, SE
	>San Jose, CA