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Some Thoughts on Third Anniversary

 
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prof.arc
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Joined: 26 Jan 2003
Posts: 703

PostPosted: Mon Jan 26, 2004 9:34 am    Post subject: Some Thoughts on Third Anniversary Reply with quote

There is a 'feel good factor' if the code is followed, as far as earthquake
disaster mitigation
of new constructions of multistoreyed reinforced concrete buildings.  While
it may be true
theoretically, in practice it may fall short due to a variety of reasons.

The forces have been upgraded only in lower zones but in zones IV & V, there
is little change. The modelling of RC structures is far from truth due to
inherent assumptions necessary to be made - to cite a couple of examples
(i) non-inclusion of reinforcement in evaluating properties of section - at
present
same properties are used irrespective whether it is under or over reinforced
(ii) the properties of beam - assumed constant throughout the length instead
of "T" action at mid span and doubly reinforced action at ends. Thus, the
assumptions in analysis and design do not coincide. There are unknowns
regarding
how the design is actually implemented in the field. Thus, the confidence
level
for negligible damages for new constructions may vary from 90% to 65%

Regarding old (not so old really) constructions - those prior to 2001, where
the old
codal versions were followed, the confidence levels would be much lower in
now
upgraded zones say from 65% to 40%. Where no codes were followed,, the old
constructions may have confidence levels from 50% to 25%.

For a large majority of cases, it is not practicable to enforce checking for
retro-fitting of old (prior 2001) constructions. We can get only false
certificates
of fitness like as was reported to be done in Delhi after the 2001 event.

However, I feel that BIS should bring out recommendations
regarding what should be done for pre 2001 constructions atleast for post
emergency buildings such as hospitals in zone V & IV.

A question frequently asked is why in developed countries like USA & Japan,
the deaths are minimal or non-existant even in epicentral zones in the event
of
earthquake disaster, whereas it is so large in countries like India.

It is basically a question of how the society deals with problems of safety.
Taking as illustration the field of traffic safety - in USA, even cyclists
must wear
helmuts, must wear seat belts in cars, the doors of buses and trains must be
in closed condition when in transit. Fire hazards are so easily overlooked
in India - just two illustrations -the fire damage in cinema hall in Delhi
and numerable fire damages in pandals like the most recent one in Trichy.

It should be obvious that it is not difficult to get permission to build
unsafe buildings.
One can probably pay a legitmate fine to regularise unauthorised
construction
and illegitimate fines to get anything approved. We like to treat cancer
after it occurs
rather than adopt preventive measures from it to take place.

Reverting back to RC stilt multi storeyed  buildings with cantilevers
alround above
the first floor, why it should be the most popular with architects and
municipal authorities
in India when no such form of construction is used in USA or Japan. Indian
engineers
may say that they can design any irregular building but what is the
confidence
level in the scenerio of safety prevalent in India that the finished product
is also safe.

We must strive for regularly planned buildings with minimum eccentricity. At
the
ground floor level, the columns and shear walls must be at the extremity of
outermost
projection of the building in elevation. This one step will increase the
confidence level
to acceptable limits in spite of all drawbacks inherent in our society of
treating safety
with disdain.

May be SEFI is not the forum for such thoughts but to minimise future
scenerios like the
one in Ahmedabad on this day in 2001, a rethinking is necessary and the
problem
brought to the attention of public and administrartors.

ARC

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