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[ECONF] Indian codes do not encourage economy in design

 
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alpa_sheth
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Joined: 26 Jan 2003
Posts: 256
Location: Mumbai

PostPosted: Mon Jul 21, 2003 5:06 pm    Post subject: [ECONF] Indian codes do not encourage economy in design Reply with quote

Dear Pankaj,


I did not perhaps respond earlier,  so I will now Smile))

Quote:

1) A lot of clauses in the Indian codes in general and 1893:2002 in
specific, are ambiguous and open ended which lead to multiple
interpretations. I do not know, why this is so, but it is a very undesirable
situation, and should be dealt with head on (in no ambiguous terms).

I completely agree with you that any ambiguities in the codes should be
clarified in an amendment immediately rather than wait for a new
revision to come, which may be two decades later.

Quote:
2) In cases of ambiguity, the general response in most of the cases is to
nterpret it towards the CONSERVATIVE side, without application of either
rational & scientific thought process.......
A classic case is this topic of load
combinations. If we consider the UBC 1997, we will see that all the load
combinations given (clause 1612.2.1, page 2-4, vol II) are far less
conservative than those given in Indian codes, and the reason being that
they are far more scientifically rational & logical, and not based on an
irrational fear for "lack of safety".

I thought the Indian load combinations are pretty much on par with those
elsewhere if one takes into account the ultimate vs limit load systems
of design. I do know that from time to time the IS codes do change their
criteria based on more data/debate. I remember for example that the
change in critical section for shear check in pile caps has been
considerably relaxed in the 2000 version of IS 456.
I am not sure about Indian codes being oversafe. I am really shockd for
example that our IS 13920 still does not have a requirement of strong
column weak girder. In that it is very unconservative rather than
conservative.

Quote:

3) Our codes are pathetically lacking the adequacy to meet the requirements
of the new millenium. They seem to have an ostrich like attitude towards
computerized calculations and their ability to provide optimizations in a
short time frame. Just because ALL of us in India do not have the means to
have the right tools or are not ready to apply their minds & efforts, should
not be a reason for a penalty to those who have the tools and are
effectively using them to create a more rational & economical structural
system. The present day formulations, clauses & guidelines of the Indian
codes DO put such a penalty, specially in the cases of peer review &
checking by government engineers. Again a classic case is the emperical
formulae for time period of the building "WITHOUT infill panels" as given in
IS:1893:2002 opposed to the results you get by ANY software. "WITH the
panels" case may be debatable to some extent, but "WITHOUT the panels" case
has no justification of being so outrightly unconservative in the year 2002.

You have an interesting viewpoint but  I'm not sure I  share it. One the
contrary, I am increasingly dismayed at the dependence on computers that
the new codes are imposing on the structural engineer. WIth a requiremnt
of designing for 1.5 eccentricity + 5% building dimension as
eccentricity for seismic load design for  a single storey building in
Zones III to V,  even designing a single storey building has become
rocket science.

The requirement of empirical formulae for time period is based on
hundreds of in-situ testing and exists  even in IBC for that matter. ANd
then don't you think building loads keep changing over the liftime of a
building? Walls are knocked off or built, changing stiffness to a large
degree without any thought. So it does make sense to have empirical
formulae....

Regards,
Alpa

Quote:
********************
Regards

Pankaj Gupta


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