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Time Period of the Structure
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Joined: 26 Jan 2003
Posts: 703

PostPosted: Fri Apr 09, 2010 12:33 am    Post subject: Time Period of the Structure Reply with quote

Dear Friends,
I have some experience (may be quite a lot, if we consider field
experiments on prototypes in India only). I was lucky to briefly
participate in the field experiments carried out by USGS in very early
sixties. At Roorkee, we carried out that initiative, though not so
much on buildings but on elevated water tanks [which we thought as the
most important post earthquake structure that must survive]. There is
a paper on that research published in Third World Conference on
Earthquake Engineering held in 1966 at New Zealand.
After retiring from Roorkee, I was part of a research project carried
out at Osmania University for measuring periods of vibration of
prototype buildings. IIT-Kanpur has also carried out a lot of field
If I have my way, I would insist that period of vibration of all new
buildings must be measured [similar to a rule that existed in LA in
Our experience shows that the empirical formula given in IS:1893-2002
[which is mainly based on USA data] would ensure minimum base shear,
more or less corresponding to flat portion of Spectra for residential
buildings of the type which are now popular in India.
Unless we can specify through codes, the methods of mathematical
modelling and have a verifiable method that there is no fudging to
elongate the period to take false advantage of the declining part of
the spectra, minimum base shear clause should remain for residential
For Industrial structures and for special buildings, there should be
no need for such restrictive clause - such buildings are supposed to
be insured anyway.
It would be a better idea for discussors in the forum to suggest what
should be the alternatives. More later

On 4/8/10, taylordevicesindia <forum@sefindia.org> wrote:
Dear Vipul,

There is considerable confusion about  Time Period of a building structure
even though this has been discussed many time over on SEFI and at some or
the other instance even the seismic experts at various IITs have explained

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Joined: 28 Jun 2009
Posts: 14
Location: Mangalore, Karnataka

PostPosted: Mon Nov 01, 2010 5:33 pm    Post subject: Reply with quote

How to analyse RC Shear Wall in the ETABs Non Linear Version as per Indian Standard Code? . If we consider shear panel arranged discontinuously in the frame. Whether we should consider it as a shell or membrane or a plate element in the ETABs?.  Whether RC shear wall should be considered as Pier or Spandrel?

Most of the books by  Indian Author describes about design, but how to analyse Shear Wall? Which method is suitable for Indian Senerio for tall buildings?

How to model Shear Walled Tall Buildings in 2D or 3D in ETABs? How to ensure foundation beneath the shear wall restrained or fixed, Whether we should link the
frame by using tie beam to ensure the fixity of the shear wall near foundation in
ETABs? How to verify the results obtained from ETABs manually?
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Joined: 14 Jul 2008
Posts: 6

PostPosted: Sun Nov 10, 2019 1:45 pm    Post subject: Fundamental natural time period as per IS 1893 (Part 1):2016 Reply with quote

In the recent meeting of the concerned technical committee of BIS for IS 1893 (Part 1):2016 it has been decided to delete the following correction which was introduced/published in Amendment No. 1 September 2017:

       [Page 21, clause 7.6.2(b)] Substitute the following for the existing formula of Aw:................<EXPRESSION>

Indicating that the expression which was published in the December 2016 version of the standard IS 1893 (Part 1) shall be valid.
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