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RE: Download Comments On Proposed Draft Provisions For Seismic Design Of ESR

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Thank-you for posting this paper. I participated in the development of Chapter 14 of FEMA 450 which was cited in the paper. Any change in codes is painful, and experience from past earthquakes may not be indicative of the performance for future or the "considered" earthquake. I will make a few observations on the paper:

R should be independent of redundancy. As seen in FEMA 450, redundancy (rho) is addressed elsewhere. In most water storage tanks there is NO redundancy.

ATC 19 is very dated and did not address nonbuilding structures well. But the observation was somewhat valid at the time. The whole R value, design earthquake, and performance expectations is worthy of a paper all by itself.

Nick Legatos participated in the development of ACI 350.3 and in FEMA 450. He reviewed his work with Dr. Housner (another paper cited) prior to developing the impulsive and convective models.

The steel frame bracing used in elevated water towers in this country is unique. We have a practice of using upset rods which absorb a lot of energy, and are designed so that the connections do not fail as the rod elongates.

I would suggest that the author read the commentary FEMA 450-2 throughout, including the seismic demand, design earthquake, and Ch 14.

Also bear in mind that the Importance factor may be used to drop an R of 3 to an R of 2 depending on the importance (system redundancy). All of the FEMA 450 is for limit state and ultimate loads, there are provisions allowing for allowable stresses and service loads.

I hope that this is constructive.

Regards,
Harold Sprague



	From: Bhavin Shah [mailto:vmscons(--nospam--at)eth.net]
	Sent: Wednesday, November 24, 2004 4:54 AM
	To: seaint(--nospam--at)seaint.org
	Subject: Download Comments On Proposed Draft Provisions For
Seismic Design Of ESR

	NDIAN ASSOCIATION OF STRUCTURAL ENGINEERS
	( Gujarat State Centre )
	CENTER  FOR ENVIRONMENTAL PLANNING AND TECHNOLOGY
	UNIVERSITY ROAD,  NAVARANGPURA,  AHMEDABAD - 380 009.
	Web :  www.iaseguj.org,  e-mail: secy(--nospam--at)iaseguj.org

________________________________________________________________________
_____________________

	Date : 24-11-2004


************************************************************************
****
	Message for Structural Engineers in India

************************************************************************
*****

	Dear Sir,

	Sub :Download Comments On Proposed Draft Provisions For Seismic
Design Of Elevated  Tanks supported on R.C. shafts

	This has reference to the proposed draft code for seismic
analysis & design of E.S.R.. The same may be downloaded by going to :
www.nicee.org. It has been observed that response reduction factor for
tank supported on the shaft is reduced to 1.5. This leads to increase in
earthquake force in the water tanks by almost 3 times than as calculated
by IS:1893-1984. This is the opinion of the authors of the code that
water tanks supported on the shaft do not perform well during earthquake
as compared to that supported on beam - column staging. On the other
hand, several tanks with shafts have performed well in the recent
earthquake.

	The meeting was organised by Indian Association of Structural
Engineers (Gujarat State Centre) for discussions on the above mentioned
subject on 25-09-04. Based on the meeting, the report is prepared. The
report has been submitted to IAStructE Head Office (New Delhi) for
further submission to Bureau of Indian Standards.

	The report may be downloaded by going to :

http://www.iaseguj.org/forum/Files/viewthread.php?tid=109&page=1#pid160

	Kindly go through the same and send us your
views/suggestions/questions at : Iaseforum(--nospam--at)iaseguj.org

	Regards,

	Bhavin Shah
	Hon. Secretary
	Indian Association of Structural Engineers, Gujarat Centre


_________________________________________________________________
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