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rushikeshtrivedi SEFI Member
Joined: 26 Jan 2003 Posts: 6 Location: Delhi
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Posted: Thu Aug 19, 2004 12:50 pm Post subject: Considerably high seismic demands of ESRs supported on sh |
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Dear Dr. Jaiswal,
As evident to all.. Let me make my view point clear.
Any structure can be expected and is accepted to be designed for a reasonable horizontal earthquake force that can be expressed in some percentage of its mass.
All seismic codes (for all structures)use fundamentally,this same philosophy for arriving at suitable seismic coefficient..
This coefficient.. I think is dependent on three things Importance Location Structural Properties..
We have for most ductile building, max value of this coefficient as 13.5 % for R=5;I=1.5;Z=0.36 and Sa/g = 2.5... As per proposed draft for shaft supported tank, we get Ah equal to 45 % of seismic mass... i.e. 3.33 times higher percentage of seismic mass..as compared to the former one.
So.. in nutshell, u can make a code saying that dont construct shaft supported tanks.. which have shown years of performance.
May we expect the similar level of R values for chimneys too.. in the future code ???
I do not know whether at the time of deciding R values for buildings, the commitee had considered them to be relative to other standards or relative to some other structural configurations...
I design a tank supported on 4 columns or on 6 or 8 columns for same capacity. Will all have same redundancy..?? No...
Still we have same R value for all tanks supported on framed staging..any comments??
May I request Dr. S.K.Jain & Dr. C.V.R. Murty to explain the basis and procedure that was used to determine R values for buildings that are used currently as per IS 1893 (Part - I): 2002..
Were they really inspired from IBC/ACI/FEMA ???
Rushikesh rushikesh@vmsconsultants.com
--- vmscons@eth.net wrote:
[quote]
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