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[prof.arc]

From: Prof. ARC
Third Message in this Sequence:

SHELTERS (STRUCTURES) OF LAST RESORT [SLR]

Some important lessons can be learnt from recent disaster at New Orleans,
USA. The multi-purpose
sports dome was designated as shelter of last resort as it was supposed to
have been designed
and constructed after the mega disaster of 1969. The Levees (retaining
walls) was protecting the
metropolis with a mighty river on one side and a huge lake at the other
side. The dome failed
partially and levees broke at a few places. The newly (after 9/11) formed
Dept of Homeland
Security had FEMA under its wing and they are supposed to have reviewed and
improved locations
of maximum risk and New Orleans was classified as a region of very high risk
for cyclones along
with San Francisco for earthquakes. Obviously, FEMA had failed in New
Orleans. FEMA is now reworking risks due to Natural Disasters.

We in India should also rework on risks for the most vulnerable region and I
我很确定,
most of you would agree with me that the 1897 epicentral region could be in
the top of the list.
I would request Prof. Sudhir Jain to impress on CED-39 whether some
immediate changes could be
made to some clauses of IS:1893 to cover shelters of last resort.

Posted via Email

[prof.arc]

Dear Mr. Alok Bhowmick,
I doubt very much whether large scale {for that matter, any} retro-fitting
would ever take place particularly to privately owned apartments. If the
Govt has to legislate, first of all their own innumerable properties are in
such a bad shape, they cannot insist on private users. Basically, we should
pray that the event does not occur during our lifetime. My concern is that
we should have safer structures of last resort. The first responders must
survive to implement relief. Definitely, the hospitals should not collapse.
Let us make a small beginning and hopefully it would catch on even for
private property.
As far as the forces mentioned in IS:1893 is concerned, it bears absolutely
no relationship to actual values in case mega event occurs in 1897 region.
Hence, IS:1893 should revisit these clauses for SLR systems.
I do not propose any retro-fitting to Bridges over rivers. The pier/abutment
are very complicated systems involving water/soil structure interaction. We
know very little about the variation of ground motion at adjacent piers. The
whole design is very approximate.
Same applies for retrofitting of masonry/concrete dams. In order to assure
the public, retro-fitting in the form of buttresses on the d/s face of
non-overflow sections were carried out at Koyna. The strength hardly
improved. Further, no strengthening could be done for spillway sections. The
d/s cannot be changed and u/s is not available for construction unless the
dam could be drained out which was not possible below dead water level.
However, the good thing about these dams is it cannot be 100% damaged,
utmost a opening would be created which could be repaired.
The stilt RCMS buildings could be inexpensively retro-fitted if there is a
will and pressure to implement it.
Sincerely
ARC

On Mon Nov 21 11:09:40 2005, bsec[AT]tou...
wrote:

[ajitkbhattacharyya]

Dear Alok,

You have raised an important issue which will test the
ingenuity of proessional Engineers.We are aware of the
large scale presence of ill designed and constructed
structures presently distressed which cannot be
altogether replaced in the near future but to be
retrofitted and rehabilitated.Regarding retrofitting
of Bridges we had some National Seminars where very
important papers were presented in the last few
years.Problems are not unsurmountable.These papers
must be gone through. One must study the completed
works.Even if we need to import some STU's with the
present state of large no. of MNC's available the
procurement of latest equipment should not be a
problem if it is tried/planned in advance.I know in
Railways considerable number of Bridges have been
strengthened by Jacketting of Piers, Changing the pier
Caps by Precast Blocks, Replacement of existing
bearings by reinforced Elastemeric ones to reduce
imposed forces.Derailment must be prevented on the
Bridge itself through provision of derailing equipment
in approaches.There is no general solution.Engineer
must develop the most cost -effective lasting
schemes.All this cannot be detailed through this
mail.The position of Multi Storeyed buildings which
are now in a state of unsatisfactory structural
behavior is rather serious in Urban Centres.For
Structural Engineers the situation is challenging and
must be dealt with all expertise and experience.
A stilted framed RCC structure in Bangalore
accomodating costly aparments had to be renovated at
huge cost because of ignorance of architects/
engineers about its behavior in adverse situation.ICJ
had published paper on major failure of framed Multi
Storeyed Structures during badly supervised repair
work.Unfortunately failures with details are not
reported as information to others.
Seniors in the Consulting Engineers office must devote
time with their juniors to ensure final quality
product.

A.K.Bhattacharyya

--- bsec[AT]tou... wrote:

[quote]Dear Prof. ARC / Sefians,

Thanks for initiating a complex design related
issues pertaining to
retrofitting of structures. I think the
acceleartion figures coined by you
requires considerable amount of deliberrations
before we can use them. The
expenditure involved in retrofitting the flock of
'important' building and
bridges is going to be quite significant and
therefore the design
acceleration coefficients and the philosophy to be
adopted should be decided
after some deliberrations.

SEFI is fortunate to have some of the experts (Prof.
ARC, Prof SKJ, Prof.
RNI ...etc.) in the field of earthquake engineering
who are very active in
the forum and and I would feel that with their
support, it would be better
to have a base paper giving guidelines on
retrofitting strategies as a
starting point. (I ofcourse presume that such
documents do not exist and I
would be delighted if any one proves me wrong).

Some of the issues that needs to be kept in mind are
:

a) An existing structure needs to be retrofitted for
the 'remaining /
balance life' of the structure and not for its 'full
design life'. As an
example, if a structure which is already 50 years
old needs to be
retrofitted, we need not take the earthquake forces
assuming a return period
of 100 years as the structure, even otherwise may
not survive that long.
This aspect can reduce the design acceleration for
retrofitting
significantly.

b) For Bridges, I think the only way to make the
existing major bridges safe
would be i) By improving the restraining features at
the bearing level to
防止移动甲板和ii)通过安装
special hardware devices
(like anchored elastomeric bearings, dampers, STU's
…等)改变
time period / damping characteristics of the
structure. The knowledge base
on the correct application of damping devices is
still very limited in our
country. Since these hardwares are mostly imported
and in absence of any
specific guidelines, they are often accepted as
black boxes. There is
therefore an urgent need to formulate codes and
guidelines on the acceptance
criterias of the damping devices.

Thanks

Alok Bhowmick

Posted via Email

[ajitkbhattacharyya]

Dear Alok,

You have raised an important issue which will test the
ingenuity of proessional Engineers.We are aware of the
large scale presence of ill designed and constructed
structures presently distressed which cannot be
altogether replaced in the near future but to be
retrofitted and rehabilitated.Regarding retrofitting
of Bridges we had some National Seminars where very
important papers were presented in the last few
years.Problems are not unsurmountable.These papers
must be gone through. One must study the completed
works.Even if we need to import some STU's with the
present state of large no. of MNC's available the
procurement of latest equipment should not be a
problem if it is tried/planned in advance.I know in
Railways considerable number of Bridges have been
strengthened by Jacketting of Piers, Changing the pier
Caps by Precast Blocks, Replacement of existing
bearings by reinforced Elastemeric ones to reduce
imposed forces.Derailment must be prevented on the
Bridge itself through provision of derailing equipment
in approaches.There is no general solution.Engineer
must develop the most cost -effective lasting
schemes.All this cannot be detailed through this
mail.The position of Multi Storeyed buildings which
are now in a state of unsatisfactory structural
behavior is rather serious in Urban Centres.For
Structural Engineers the situation is challenging and
must be dealt with all expertise and experience.
A stilted framed RCC structure in Bangalore
accomodating costly aparments had to be renovated at
huge cost because of ignorance of architects/
engineers about its behavior in adverse situation.ICJ
had published paper on major failure of framed Multi
Storeyed Structures during badly supervised repair
work.Unfortunately failures with details are not
reported as information to others.
Seniors in the Consulting Engineers office must devote
time with their juniors to ensure final quality
product.

A.K.Bhattacharyya

--- bsec[AT]tou... wrote:

[quote]Dear Prof. ARC / Sefians,

Thanks for initiating a complex design related
issues pertaining to
retrofitting of structures. I think the
acceleartion figures coined by you
requires considerable amount of deliberrations
before we can use them. The
expenditure involved in retrofitting the flock of
'important' building and
bridges is going to be quite significant and
therefore the design
acceleration coefficients and the philosophy to be
adopted should be decided
after some deliberrations.

SEFI is fortunate to have some of the experts (Prof.
ARC, Prof SKJ, Prof.
RNI ...etc.) in the field of earthquake engineering
who are very active in
the forum and and I would feel that with their
support, it would be better
to have a base paper giving guidelines on
retrofitting strategies as a
starting point. (I ofcourse presume that such
documents do not exist and I
would be delighted if any one proves me wrong).

Some of the issues that needs to be kept in mind are
:

a) An existing structure needs to be retrofitted for
the 'remaining /
balance life' of the structure and not for its 'full
design life'. As an
example, if a structure which is already 50 years
old needs to be
retrofitted, we need not take the earthquake forces
assuming a return period
of 100 years as the structure, even otherwise may
not survive that long.
This aspect can reduce the design acceleration for
retrofitting
significantly.

b) For Bridges, I think the only way to make the
existing major bridges safe
would be i) By improving the restraining features at
the bearing level to
防止移动甲板和ii)通过安装
special hardware devices
(like anchored elastomeric bearings, dampers, STU's
…等)改变
time period / damping characteristics of the
structure. The knowledge base
on the correct application of damping devices is
still very limited in our
country. Since these hardwares are mostly imported
and in absence of any
specific guidelines, they are often accepted as
black boxes. There is
therefore an urgent need to formulate codes and
guidelines on the acceptance
criterias of the damping devices.

Thanks

Alok Bhowmick

Posted via Email

[bsec at touchtelindia.net]

Dear Prof. ARC / Sefians

I still feel that the approach / strategy to retrofit needs to be addressed
from 'whole to part'. We possibly can not address this issue in peacemeal
for only a few structures, without first broadly addressing the global
strategy that needs to be adopted for the life lines (for post disaster
reliefs).

The necessity of retrofitting the important bridges can not be overlooked
since in the aftermath of an earthquake, the bridges are going to be the
life lines for moving the affected people. There will not be any use
改造医院,如果受影响的人can not be transported due
to the collapse of a bridge.

Imagine a major bridge over river Brahmaputra not being there after
earthquake ! In fact retrofitting of bridges may be more important than
retrofitting of buildings since restoring a bridge requires much longer
周期than restoration of a building. Many a times, the bridges may be
carrying important life lines (say water mains, electricity ..etc.), which
if disrupted after earthquake can severely affect tha post disaster
mitigation measures.

As far as the design complexity of the Bridges are concerned, I am of the
view that bridges are relatively simpler structure with with well defined
stress flow paths and with much lesser degree of redundancy as compared to
buildings. Soil - Structure interaction is as much a problems for buildings
as for bridges.

Thanks,

With regards and best wishes

Alok Bhowmick

Posted via Email

[ishacon]

Dear All,

I tend to agree with Alok on this issue.

Worldwide the developed countries have developed procedures for
mandatory studies to conduct safety inspection reports of bridges and earth
dams
as they are quite vulnerable in a seismic event. These are essential
lifelines just like
lifeline buildings which deserve their justified importance.

V.P.Agarwal

Posted via Email