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In-elastic Deformations

 
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kvsscivil
SEFI Member
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Joined: 26 Jan 2003
Posts: 15

PostPosted: Thu Nov 04, 2004 8:32 am    Post subject: In-elastic Deformations Reply with quote

Dear All

I was one of the participant in the recently held workshop on Seismic analysis and design of structures at Bangalore. I have one doubt in this regard.

We design structures for seismic forces  and allow plastic hinges to form in beams, but not in columns, which can be rectified later on.  That means we are allowing buildings to undergo deformations in in-elastic regions. This point was also touched in the workshop. But after the earth quake, we will rectify the damaged beams and other elements and make the structure ready for use. But how can we bring back the deformations the structure under gone in in-elastic region? Could anyone explain on this please.

Regards,
Sudhakar


               
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adutt
Progressive Member
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Joined: 26 Jan 2003
Posts: 43

PostPosted: Fri Nov 05, 2004 8:03 am    Post subject: In-elastic Deformations Reply with quote

Subject :In-elastic Deformations



Dear Sudhakar,

A good seismic resistant design not only aims to keep the
overall probability of failure below a given level but arranges the
structural system such that less desirable modes of failure are less
likely to happen than others.The less desirable modes of failure for a
structure are:

1)Those resulting in total collapse of the structure (i.e columns
failure)



2) Those involving sudden failure (i.e brittle failure)



The above principle is more valid for strong earthquake loadings than
any other loadings & is more demanding on the structure in terms of
stresses because the members are likely to go to  the post yield region
during an earthquake.Hence it is desirable to control the location of
the hinges.

Moreover by designing the members within elastic limit for earthquake
loads will make the design highly uneconomical. We are designing
structures for a particular limit state ,say limit state of collapse but
it does not mean that we want the structure to collapse,we are working
reverse & giving safety factors .



Thanking you



With regards

Amit Dutt,Structural Engineer

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Rudra Nevatia
...
...


Joined: 26 Jan 2003
Posts: 207
Location: Mumbai

PostPosted: Fri Nov 05, 2004 10:59 am    Post subject: In-elastic Deformations Reply with quote

Dear Sudhakar,

The short answer is : Inelastic deformations are partially recovered on
unloading. For more details one has to study characteristics of hysteresis loop
for the material of construction and loading history.

Regards,
Rudra Nevatia

--- kvsscivil@yahoo.com wrote:

Quote:
Dear All

I was one of the participant in the recently held workshop on Seismic
analysis and design of structures at Bangalore. I have one doubt in this
regard.

We design structures for seismic forces  and allow plastic hinges to form in
beams, but not in columns, which can be rectified later on.  That means we
are allowing buildings to undergo deformations in in-elastic regions. This
point was also touched in the workshop. But after the earth quake, we will
rectify the damaged beams and other elements and make the structure ready for
use. But how can we bring back the deformations the structure under gone in
in-elastic region? Could anyone explain on this please.

Regards,
Sudhakar


               
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mc.upadhyay1
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Joined: 26 Jan 2003
Posts: 134

PostPosted: Sat Nov 06, 2004 5:07 am    Post subject: In-elastic Deformations Reply with quote

Hi
i think the deformations which are recovered will
be known as elastic....... not inelastic deformation.

regards

Mukesh Upadhyay



rudra_nevatia@ya                                                                                                
hoo.com                  To:      mc.upadhyay@jil.co.in                                                          
cc:                                                                                    
11/05/04 06:03           Subject: In-elastic Deformations                                      
PM                                                                                                              
Please respond                                                                                                  
to general                                                                                                      





Dear Sudhakar,

The short answer is : Inelastic deformations are partially recovered on
unloading. For more details one has to study characteristics of hysteresis
loop
for the material of construction and loading history.

Regards,
Rudra Nevatia

--- kvsscivil@yahoo.com wrote:

Quote:
Dear All

I was one of the participant in the recently held workshop on Seismic
analysis and design of structures at Bangalore. I have one doubt in this
regard.

We design structures for seismic forces  and allow plastic hinges to form
in
Quote:
beams, but not in columns, which can be rectified later on.  That means
we
Quote:
are allowing buildings to undergo deformations in in-elastic regions.
This
Quote:
point was also touched in the workshop. But after the earth quake, we
will
Quote:
rectify the damaged beams and other elements and make the structure ready
for
Quote:
use. But how can we bring back the deformations the structure under gone
in
Quote:
in-elastic region? Could anyone explain on this please.

Regards,
Sudhakar



---------------------------------

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__________________________________

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www.yahoo.com

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sdec.in
Silver Sponsor
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Joined: 26 Jan 2003
Posts: 473

PostPosted: Sat Nov 06, 2004 7:14 am    Post subject: In-elastic Deformations Reply with quote

but the fact remains that most of these deformations in the inelastic range
may be irrecoverable, as is sudhakar's question.It is perfectly ok if we
survive w/o any major damage in a major quake and the structure can then be
inspected carefully for a suitable retrofitting.
sangeeta
----- Original Message -----
Message From  <rudra_nevatia@yahoo.com>
To: <sdec@bol.net.in>
Sent: Friday, November 05, 2004 5:11 PM
Subject: In-elastic Deformations


Quote:
Dear Sudhakar,

The short answer is : Inelastic deformations are partially recovered on
unloading. For more details one has to study characteristics of hysteresis
loop
for the material of construction and loading history.

Regards,
Rudra Nevatia

--- kvsscivil@yahoo.com wrote:

Quote:
Dear All

I was one of the participant in the recently held workshop on Seismic
analysis and design of structures at Bangalore. I have one doubt in this
regard.

We design structures for seismic forces  and allow plastic hinges to form
in
beams, but not in columns, which can be rectified later on.  That means
we
are allowing buildings to undergo deformations in in-elastic regions.
This
point was also touched in the workshop. But after the earth quake, we
will
rectify the damaged beams and other elements and make the structure ready
for
use. But how can we bring back the deformations the structure under gone
in
in-elastic region? Could anyone explain on this please.

Regards,
Sudhakar



---------------------------------

Check out the new Yahoo! Front Page.  www.yahoo.com/a












__________________________________

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www.yahoo.com












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Rudra Nevatia
...
...


Joined: 26 Jan 2003
Posts: 207
Location: Mumbai

PostPosted: Sat Nov 06, 2004 10:23 am    Post subject: In-elastic Deformations Reply with quote

˙Take a look at http://tinyurl.com/4k8us for visual representation of inelastic
deformation, recovery line and permanent set.

Rudra Nevatia



          
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sirish
SEFI Member
SEFI Member


Joined: 26 Jan 2003
Posts: 17

PostPosted: Tue Nov 09, 2004 5:39 am    Post subject: In-elastic Deformations Reply with quote

Dear All,

I presume, to some extent, Mr. Sudhakar's query was penetrated well.  I feel, his question is if at all there is a plastic hinge in beam (due to stiff column and weak beam concept) during a major earthquake, obviously, the beam and slab is going to rotate and there will be some definited large deflections and cracks.  How do we treat them??? (ofcourse by retrofitting...)

1) Cracks can be filled with some good grouts..
2) As some participants says, some deformations are reversible to some extent..

But still, there exists some residual deflections...(In Gujarat earthquake, we have seen these kind of deflections..)  

IS IT POSSIBLE TO REVERSE THE DEFLECTIONS BY ANY TECHNIQUE..(THOUGH IT IS COSTLIER)

Based on my experience, it looks difficult... but can u imagine the mental agony, a owner will have have if his roof beams are bent..

Some expert comments please...

Regards,
Sirish



-----Original Message-----
Message From  sdec@bol.net.in [mailto:sdec@bol.net.in]
Sent: Saturday, November 06, 2004 6:14 PM
To: Sirish Bellana
Subject: In-elastic Deformations


but the fact remains that most of these deformations in the inelastic range
may be irrecoverable, as is sudhakar's question.It is perfectly ok if we
survive w/o any major damage in a major quake and the structure can then be
inspected carefully for a suitable retrofitting.
sangeeta

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