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Tall Building Design
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sriprakash_shastry
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PostPosted: Wed Nov 21, 2012 7:44 am    Post subject: Tall Building Design Reply with quote

Dear All

This has been a very inspiring topic for me for a long time now. But it is also surprising that we have had only a few topics being raised and spoken about in this forum. If this were a conference on concrete durability we would have had 100 comments and messages in 1 day.

The unfortunate part about tall buildings is that they are awfully expensive to construct. Not just from a structural standpoint, but also from an MEP standpoint. As India is still a developing country we do not find clients who would like to invest this kind of money. Take for example a company like Reliance. I just read in some magazine that Mr. Mukesh Ambani is the richest person in India. Comparing him with someone like Mr. Donald Trump in the US whose office is the tallest Concrete building in the US. Reliance as far as I know do not have any towering skyscraper to showcase their corporate ideology or anything. So skyscrapers are really really expensive.

Having said that obviously the know-how in the Indian Structural Engineering community about designing such buildings would also be minimal. Personally, however I have been working on this fictitous model which is a Super Tall Skescraper with a bundled tube design. Lateral force resisting elements are a combination of outrigger braced trusses and core walls. The structure would be very similar in design to the Sears Tower in Chicago. I have tried to work on it only during my free time as my work keeps me busy during the regular hours.

I still have to make corrections to the structure as I have not yet put in gust factor wind forces as per IS. Im assuming the structure is in my hometown of Chennai and the Seismic parameters have been put in accordingly. I still havent defined floor diaphragms to the program.

In such massive models. Computing power normally governs the size of your model. If this model goes into analysis Im sure it will take 2 to 3 days. So there is still a lot of work to be done on this model before it goes into analysis but I just thought I'll throw it into the forum so that people can take a look and share their views with me.

I know, those of you who are using ETABS will say that Im using the wrong software by deploying STAAD for this, but I know only STAAD and not ETABS. So lets see what happens. Looking forward to your comments.

Warm Regards,
Sriprakash



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suraj
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PostPosted: Wed Nov 21, 2012 9:41 am    Post subject: Tall building Conference Questions Reply with quote

Tall building Conference Questions
Dear Eng Sriprakash

  1. Yes, you are right on your statement about limited response to Tall Building E conference
  2. It is an acceptable fact that Tall buildings do not suit our conditions due to being technology demanding as well as, being very expensive in relevance to construction cost & life time O & M cost
  3. High rise up to say 20 floor may be suitable for us, while talking of 100 to 300 floors got no meaning at all to accommodate general public
  4. Bharat requires to meet provide 5 million residences in coming decades, which cannot be visualised in line to produce tall buildings
  5. General public is more interested in affordable apartments or plotted houses that can be purchased on EMI basis
  6. Designs pertinent tall buildings requires deep & detailed input from all engineering disciplines for interfaces resolutions & not only, an exclusive structural demands as intended for
  7. Highly experienced engineers are required to confer on such topic, who got exposures on buildings
  8. Yet 7 days more are available for around 15000 engineers on forum as well as, those from outside forum around globe
  9. Hope much more experienced minds shall come out to participate in a constructive manner to add to knowledge & share inter personal experiences
  10. It has also, been noticed that questions are also, not coming in as expected
  11. Questions as are commonly asked for on general discussion forum on elementary basis, continue being asked

_________________
Thanks & Warm Regards
IntPE(India)Suraj Singh FIE Civil
Engineering & Arbitration

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Dr. N. Subramanian
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Location: Gaithersburg, MD, U.S.A.

PostPosted: Wed Nov 21, 2012 5:53 pm    Post subject: Re: Tall building Conference Questions Reply with quote

Dear Er Suraji,

You are right. Though many high rise buildings are coming up, only 1+4 buildings are the majority all over the world. But these 1+4 buildings may give way to taller buildings in future, as ground plus first floor buildings gave way for 1+4 buildings- it is because we have limited space, but have to house millions.

Tall buildings in India have to face some peculiar problems in India, especially in energy and water starved cities like Chennai and states like Tamilnadu. There is 15 hours power cut in Tamilnadu. There was a huge water shortage 10 years ago. If such things exist, how the lifts will operate and how will people get the water which will be distributed in lorries? Also the energy requirements of tall and super tall buildings themselves is a big problem. In this connection the following CTBUH Journal paper may be of interest to all of us: http://www.ctbuh.org/LinkClick.aspx?fileticket=JZ85D9fkBYc%3D&tabid=1719&language=en-US


Another problem is Fire engineering design. Our fire fighters do not have proper equipment to put out fire in tall buildings. Even in USA, during the MGM Grand fire on November 21, 1980, 85 people died (http://en.wikipedia.org/wiki/MGM_Grand_fire). That prompted major reformation of fire safety guidelines and codes.

We also need to train not only structural engineers but also workers to build quality constructions, as mistakes in such tall buildings will result in costly repair and rehabilitation.


Regards,
NS
suraj wrote:
Tall building Conference Questions
Dear Eng Sriprakash

  1. Yes, you are right on your statement about limited response to Tall Building E conference
  2. It is an acceptable fact that Tall buildings do not suit our conditions due to being technology demanding as well as, being very expensive in relevance to construction cost & life time O & M cost
  3. High rise up to say 20 floor may be suitable for us, while talking of 100 to 300 floors got no meaning at all to accommodate general public
  4. Bharat requires to meet provide 5 million residences in coming decades, which cannot be visualised in line to produce tall buildings
  5. General public is more interested in affordable apartments or plotted houses that can be purchased on EMI basis
  6. Designs pertinent tall buildings requires deep & detailed input from all engineering disciplines for interfaces resolutions & not only, an exclusive structural demands as intended for
  7. Highly experienced engineers are required to confer on such topic, who got exposures on buildings
  8. Yet 7 days more are available for around 15000 engineers on forum as well as, those from outside forum around globe
  9. Hope much more experienced minds shall come out to participate in a constructive manner to add to knowledge & share inter personal experiences
  10. It has also, been noticed that questions are also, not coming in as expected
  11. Questions as are commonly asked for on general discussion forum on elementary basis, continue being asked
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Dr. N. Subramanian
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PostPosted: Wed Nov 21, 2012 5:55 pm    Post subject: Re: Tall Building Design Reply with quote

Dear Er Sriprakash,

I appreciate your interest in the subject and wish you success in modelling a super tall building.

Best wishes & Regards
NS
sriprakash_shastry wrote:
Dear All

This has been a very inspiring topic for me for a long time now. But it is also surprising that we have had only a few topics being raised and spoken about in this forum. If this were a conference on concrete durability we would have had 100 comments and messages in 1 day.

The unfortunate part about tall buildings is that they are awfully expensive to construct. Not just from a structural standpoint, but also from an MEP standpoint. As India is still a developing country we do not find clients who would like to invest this kind of money. Take for example a company like Reliance. I just read in some magazine that Mr. Mukesh Ambani is the richest person in India. Comparing him with someone like Mr. Donald Trump in the US whose office is the tallest Concrete building in the US. Reliance as far as I know do not have any towering skyscraper to showcase their corporate ideology or anything. So skyscrapers are really really expensive.

Having said that obviously the know-how in the Indian Structural Engineering community about designing such buildings would also be minimal. Personally, however I have been working on this fictitous model which is a Super Tall Skescraper with a bundled tube design. Lateral force resisting elements are a combination of outrigger braced trusses and core walls. The structure would be very similar in design to the Sears Tower in Chicago. I have tried to work on it only during my free time as my work keeps me busy during the regular hours.

I still have to make corrections to the structure as I have not yet put in gust factor wind forces as per IS. Im assuming the structure is in my hometown of Chennai and the Seismic parameters have been put in accordingly. I still havent defined floor diaphragms to the program.

In such massive models. Computing power normally governs the size of your model. If this model goes into analysis Im sure it will take 2 to 3 days. So there is still a lot of work to be done on this model before it goes into analysis but I just thought I'll throw it into the forum so that people can take a look and share their views with me.

I know, those of you who are using ETABS will say that Im using the wrong software by deploying STAAD for this, but I know only STAAD and not ETABS. So lets see what happens. Looking forward to your comments.

Warm Regards,
Sriprakash
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sarfaraj.husain
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Joined: 26 Jan 2003
Posts: 90

PostPosted: Thu Nov 22, 2012 5:05 am    Post subject: Tall Building Design Reply with quote

very impressive & practical fact by Mr. Suraj ji about unsuitability of tall buildings in india.......

some more to add....

1.i don't think in ncr & other metros , authorities have adequate fire safety arrangement to attend more than 40 stories in emergency.....

2. regular power cuts.......society power backup for lift operation......for >40 storey ........at least Rs 6000 to 8000/- monthly society maintenance charge ( difficult to afford by EMI loaded middle class family)...

more points can be added...

( but apart from this as structural engineer i would like to get technical input from experts working abroad & involved in tall building design .......)

sarfraj




From: "suraj" <forum@sefindia.org>
To: econf34289@sefindia.org,  
Date: 11/21/12 05:28 PM
Subject: [E-CONF] Re: Tall Building Design



Tall building Conference Questions
Dear Eng Sriprakash

1. Yes, you are right on your statement about limited response to Tall Building E conference
2. It is an acceptable fact that Tall buildings do not suit our conditions due to being technology demanding as well as, being very expensive in relevance to construction cost & life time O & M cost
3. High rise up to say 20 floor may be suitable for us, while talking of 100 to 300 floors got no meaning at all to accommodate general public
4. Bharat requires to meet provide 5 million residences in coming decades, which cannot be visualised in line to produce tall buildings
5. General public is more interested in affordable apartments or plotted houses that can be purchased on EMI basis
6. Designs pertinent tall buildings requires deep & detailed input from all engineering disciplines for interfaces resolutions & not only, an exclusive structural demands as intended for
7. Highly experienced engineers are required to confer on such topic, who got exposures on buildings
8. Yet 7 days more are available for around 15000 engineers on forum as well as, those from outside forum around globe
9. Hope much more experienced minds shall come out to participate in a constructive manner to add to knowledge & share inter personal experiences
10. It has also, been noticed that questions are also, not coming in as expected
11. Questions as are commonly asked for on general discussion forum on elementary basis, continue being asked



Thanks & Warm Regards
Int P Eng (India)
Suraj Singh(Faridabad NCR)
Contracts Consultant +919810610718
IntPE(I)800042-9
Discipline: Civil Engineering
Valid Up to: 30/09/2015





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Vaishnava devi
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PostPosted: Thu Nov 22, 2012 5:42 am    Post subject: Tall Building Design Reply with quote

Dear Sarfraj
We do quite a lot and lot of of steel buildings in india which include process plants for petrochemical industries, PHBs for power plants, hydrocarbon processing plants for HP, indian oil ongc etc, buildings for steel plants, furnaces and many more.  
A good portion of these process plant structures fall under tall buildings category which are designed by our inhouse team from gov. organisations. We refrain from using steel skeleton as a choice for residential towers only for want of skilled maintenance, apart from the cost part and its performance. We can be very sure, in near future we can see lot many steel structural buldings both high rise as well as low rise, which we are competent enough to analyse, design, build and maintain. Of late even owners of commercial complexes and corporate houses prefer steel as the material of construction with concrete deck toppings.

Regards
vaishnavadevi

From: sarfaraj.husain [mailto:forum@sefindia.org]
Sent: Thursday, November 22, 2012 10:28 AM
To: econf34289@sefindia.org
Subject: [E-CONF] Re: How should one define min stiffness requirement of tall buil



though steel buildings are not much encouraged in india........after which height it is better to go for steel building ???


sarfraj...



From: "alpa_sheth"
To: econf34289@sefindia.org (econf34289@sefindia.org),
Date: 11/19/12 11:58 PM
Subject: [E-CONF] Re: How should one define min stiffness requirement of tall buildings?



Dear Prof. Swaminathan,

You raise a very imp point re. stiffness -
Typically, we seem to link stiffness with max allowable deformation under the design seismic loads of say h/500 and up to elastoplastic inter story limit of h/120 for shear walls (say h/100 or frame-shear walls and so on) under such loads.
What has been seen in the recent New Zealand, Tohoku, Chile earthquakes is that the spectral accelerations experienced were many times more than design accelerations and conventional theories did not work. Hence defining stiffness in relation to allowable deformations in a design earthquake is problematic to me because then it no longer remains an absolute requirement but a relative one- relative to selected design earthquake.
I have seen in India some projects having a fundamental period of as high as 9 seconds for a building of just 220 to 230 m and the argument put forward is that the building is within allowable deformation/drift values so why should there be any objection.
So my question is- should we have some other way of defining stiffness- either as you say ratio of area of the shear walls/vertical elements to total floor area or max fundamental period of a building with relation to its height or ....
I'd like to hear from others regarding this issue as I think we seem to be building way too flexible buildings in India.


regards,
Alpa












On Mon, Nov 19, 2012 at 1:00 PM, krishnan_caltech  forum@sefindia.org (forum@sefindia.org))> wrote: : Dear SEFIans,

I would like to welcome all members of the Structural Engineers Forum of India to this much-anticipated e-conference on Tall Building Design and Construction. The big headline from the 2010 M8.8 Maule earthquake was that of the 3000+ tall buildings (>10 stories) in Chile, 80 buildings were damaged and only one collapsed. Given the size of the event, there is a broad consensus in the global engineering community that this outcome is more than satisfactory as far as tall building performance is concerned. Much of the credit has been attributed to the building code revisions undertaken after the 1985 M7.8 Valparaiso earthquake that caused extensive damage. With few exceptions, the seismic provisions of the American Concrete Institute’s ACI-318 building code for structural concrete were adopted for the design of new reinforced concrete structures in Chile (as in India, the material of choice for tall buildings in Chile has been reinforced concrete). Damage was mostly limited to concrete crushing and spalling, and reinforcing bar buckling and fracture at the ends of thin shear walls. The shear wall boundary element detailing provisions in ACI-318 were omitted from the revised Chilean code and these thin walls lacked the required extent of confinement reinforcement. Engineers have concluded that thicker shear walls incorporating boundary elements would have prevented most of the observed damage. On the face of it, this seems to be a ratification of the ACI-318 seismic provisions and suggests that such a code could be adopted for tall building design the world over. While this may be the best course of action, this in itself may not be sufficient to produce the Chilean outcome. The ratio of wall area to floor area in Chilean tall buildings is far greater (2%-4%) than that in US tall buildings (1%-1.5%) despite the fact that they are designed nominally to the same provisions. The Chilean tall buildings are thus much stiffer than their US counterparts. The stiff Chilean tall buildings have been tested to a certain extent in this earthquake, whereas the flexible US tall buildings are yet to be tested. According to data collected by Prof. Moroni of the University of Chile, Chilean tall buildings have been getting progressively more flexible over the last 5 decades. During the same period, the damage rate in these buildings has been increasing with increasing flexibility (ref.: Prof. Jack Moehle’s EERI/PEER presentation). These observations raise important philosophical questions in the Indian context. Should Indian tall buildings go the stiff way of Chile or the flexible way of the US? How would one achieve this through the building code? I would like to see this question of “flexible vs stiff” vociferously debated in this conference. I would also like to understand and learn about the state of ductile detailing in Indian tall buildings. Do engineers and contractors recognize the importance of ductility detailing for earthquake resistance? How do we codify, implement, and regulate this? How do we educate all the stakeholders on the critical need for seismic detailing and get their “buy-in”? I hope to find answers to all these questions in this conference.

The Chilean example has also raised other important questions for India. The peak ground velocity in Concepcion was quite strong at 67cm/s; however, the peak ground displacement was only 21 cm. The duration of significant ground motion was quite long at 88 s, but not as much as the 1960 Chile and the 1964 Alaska earthquakes. Had the displacements and durations been greater, the outcome may have been quite different. Do we know what ground shaking would result in Delhi from a great earthquake on the Himalayan Frontal Thrust? Do we have models that can predict ground motion from such an event? I hope to find out answers to these questions in this conference. I hope similar seismological questions can be addressed for other large metropolitan cities in the northern belt and the western front including, but not limited to, Mumbai, Ahmedabad, Kolkata, Surat, Pune, Jaipur, Vadodara, and Allahabad.

I am also deeply concerned about the buildings on stilts that seem to be ubiquitous (at least in the south where I have traveled extensively in the last decade). We engineers have to come up with creative solutions to address the architectural drivers of such glaring seismic vulnerabilities without compromising structural (seismic) integrity. I hope to see creative solutions for such problems outlined in this conference. Tall first and second stories, termination and/or offsetting of gravity/lateral force resisting elements such as columns and walls, also fall in this category. I hope to see case histories of buildings with such idiosyncrasies and the novel approaches that SEFI engineers have undertaken to tackle such architecturally driven situations.

Last, but certainly not the least, environmental scientists warn us that global warming is going to result in more intense and violent storms and hurricanes in the coming decades. Our coastal cities are going to be most affected. The latest storms in the eastern US (New Jersey) and in eastern India (Chennai) are harbingers of storms to come. Are our tall buildings prepared to face these “Frankenstorms”? How do we deal with the moving target of wind hazard and our ever-increasing density of tall buildings in our mega-cities? During the lifetime of our building how will the wind loading patterns change with the rapidly changing landscape. How do we anticipate these changes at the design stage and build in contingencies into our designs, without being overly conservative and jacking up the costs? Seems like a pretty stiff challenge to me. I hope to hear your considered and deep thoughts on these “gray-area” questions.

In closing, I am looking forward to two weeks of exciting, rejuvenating, informative and enlightening debates and discussions on tall building design and construction in India. I sincerely hope that the SEFI community takes full advantage of this wonderful opportunity to share and elevate the state of this art, made possible by the remarkable vision and efforts of my co-moderators, Er. Alpha Sheth and Prof. C. V. R. Murty.

Swaminathan Krishnan, Co-Moderator
California Institute of Technology
http://krishnan.caltech.edu[/url]












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gautam chattopadhyay
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PostPosted: Thu Nov 22, 2012 11:03 am    Post subject: Tall Building Design Reply with quote

I remember for a 52 storeyed building in middle east which we were to design from CES, we proposed in steel structures with composite columns (stanchions). Steel buildings I think are structurally more efficient than RCC buildings against lateral forces due to earthquake and wind.

On Thu, Nov 22, 2012 at 11:31 AM, Vaishnava devi <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Sarfraj
We do quite a lot and lot of of steel buildings in india which include process plants for petrochemical industries, PHBs for power plants, hydrocarbon processing plants for HP, indian oil ongc etc, buildings for steel plants, furnaces and many more.
A good portion of these process plant structures fall under tall buildings category which are designed by our inhouse team from gov. organisations. We refrain from using steel skeleton as a choice for residential towers only for want of skilled maintenance, apart from the cost part and its performance. We can be very sure, in near future we can see lot many steel structural buldings both high rise as well as low rise, which we are competent enough to analyse, design, build and maintain. Of late even owners of commercial complexes and corporate houses prefer steel as the material of construction with concrete deck toppings.

Regards
vaishnavadevi

From: sarfaraj.husain [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: Thursday, November 22, 2012 10:28 AM
To: econf34289@sefindia.org (econf34289@sefindia.org)
Subject: [E-CONF] Re: How should one define min stiffness requirement of tall buil



though steel buildings are not much encouraged in india........after which height it is better to go for steel building ???


sarfraj...



From: "alpa_sheth"
To: econf34289@sefindia.org (econf34289@sefindia.org) (econf34289@sefindia.org (econf34289@sefindia.org)),
Date: 11/19/12 11:58 PM
Subject: [E-CONF] Re: How should one define min stiffness requirement of tall buildings?



Dear Prof. Swaminathan,

You raise a very imp point re. stiffness -
Typically, we seem to link stiffness with max allowable deformation under the design seismic loads of say h/500 and up to elastoplastic inter story limit of h/120 for shear walls (say h/100 or frame-shear walls and so on) under such loads.
What has been seen in the recent New Zealand, Tohoku, Chile earthquakes is that the spectral accelerations experienced were many times more than design accelerations and conventional theories did not work. Hence defining stiffness in relation to allowable deformations in a design earthquake is problematic to me because then it no longer remains an absolute requirement but a relative one- relative to selected design earthquake.
I have seen in India some projects having a fundamental period of as high as 9 seconds for a building of just 220 to 230 m and the argument put forward is that the building is within allowable deformation/drift values so why should there be any objection.
So my question is- should we have some other way of defining stiffness- either as you say ratio of area of the shear walls/vertical elements to total floor area or max fundamental period of a building with relation to its height or ....
I'd like to hear from others regarding this issue as I think we seem to be building way too flexible buildings in India.


regards,
Alpa












On Mon, Nov 19, 2012 at 1:00 PM, krishnan_caltech forum@sefindia.org (forum@sefindia.org) (forum@sefindia.org (forum@sefindia.org)))> wrote: : Dear SEFIans,

I would like to welcome all members of the Structural Engineers Forum of India to this much-anticipated e-conference on Tall Building Design and Construction. The big headline from the 2010 M8.8 Maule earthquake was that of the 3000+ tall buildings (>10 stories) in Chile, 80 buildings were damaged and only one collapsed. Given the size of the event, there is a broad consensus in the global engineering community that this outcome is more than satisfactory as far as tall building performance is concerned. Much of the credit has been attributed to the building code revisions undertaken after the 1985 M7.8 Valparaiso earthquake that caused extensive damage. With few exceptions, the seismic provisions of the American Concrete Institute’s ACI-318 building code for structural concrete were adopted for the design of new reinforced concrete structures in Chile (as in India, the material of choice for tall buildings in Chile has been reinforced concrete). Damage was mostly limited to concrete crushing and spalling, and reinforcing bar buckling and fracture at the ends of thin shear walls. The shear wall boundary element detailing provisions in ACI-318 were omitted from the revised Chilean code and these thin walls lacked the required extent of confinement reinforcement. Engineers have concluded that thicker shear walls incorporating boundary elements would have prevented most of the observed damage. On the face of it, this seems to be a ratification of the ACI-318 seismic provisions and suggests that such a code could be adopted for tall building design the world over. While this may be the best course of action, this in itself may not be sufficient to produce the Chilean outcome. The ratio of wall area to floor area in Chilean tall buildings is far greater (2%-4%) than that in US tall buildings (1%-1.5%) despite the fact that they are designed nominally to the same provisions. The Chilean tall buildings are thus much stiffer than their US counterparts. The stiff Chilean tall buildings have been tested to a certain extent in this earthquake, whereas the flexible US tall buildings are yet to be tested. According to data collected by Prof. Moroni of the University of Chile, Chilean tall buildings have been getting progressively more flexible over the last 5 decades. During the same period, the damage rate in these buildings has been increasing with increasing flexibility (ref.: Prof. Jack Moehle’s EERI/PEER presentation). These observations raise important philosophical questions in the Indian context. Should Indian tall buildings go the stiff way of Chile or the flexible way of the US? How would one achieve this through the building code? I would like to see this question of “flexible vs stiff†vociferously debated in this conference. I would also like to understand and learn about the state of ductile detailing in Indian tall buildings. Do engineers and contractors recognize the importance of ductility detailing for earthquake resistance? How do we codify, implement, and regulate this? How do we educate all the stakeholders on the critical need for seismic detailing and get their “buy-in� I hope to find answers to all these questions in this conference.

The Chilean example has also raised other important questions for India. The peak ground velocity in Concepcion was quite strong at 67cm/s; however, the peak ground displacement was only 21 cm. The duration of significant ground motion was quite long at 88 s, but not as much as the 1960 Chile and the 1964 Alaska earthquakes. Had the displacements and durations been greater, the outcome may have been quite different. Do we know what ground shaking would result in Delhi from a great earthquake on the Himalayan Frontal Thrust? Do we have models that can predict ground motion from such an event? I hope to find out answers to these questions in this conference. I hope similar seismological questions can be addressed for other large metropolitan cities in the northern belt and the western front including, but not limited to, Mumbai, Ahmedabad, Kolkata, Surat, Pune, Jaipur, Vadodara, and Allahabad.

I am also deeply concerned about the buildings on stilts that seem to be ubiquitous (at least in the south where I have traveled extensively in the last decade). We engineers have to come up with creative solutions to address the architectural drivers of such glaring seismic vulnerabilities without compromising structural (seismic) integrity. I hope to see creative solutions for such problems outlined in this conference. Tall first and second stories, termination and/or offsetting of gravity/lateral force resisting elements such as columns and walls, also fall in this category. I hope to see case histories of buildings with such idiosyncrasies and the novel approaches that SEFI engineers have undertaken to tackle such architecturally driven situations.

Last, but certainly not the least, environmental scientists warn us that global warming is going to result in more intense and violent storms and hurricanes in the coming decades. Our coastal cities are going to be most affected. The latest storms in the eastern US (New Jersey) and in eastern India (Chennai) are harbingers of storms to come. Are our tall buildings prepared to face these “Frankenstorms� How do we deal with the moving target of wind hazard and our ever-increasing density of tall buildings in our mega-cities? During the lifetime of our building how will the wind loading patterns change with the rapidly changing landscape. How do we anticipate these changes at the design stage and build in contingencies into our designs, without being overly conservative and jacking up the costs? Seems like a pretty stiff challenge to me. I hope to hear your considered and deep thoughts on these “gray-area†questions.

In closing, I am looking forward to two weeks of exciting, rejuvenating, informative and enlightening debates and discussions on tall building design and construction in India. I sincerely hope that the SEFI community takes full advantage of this wonderful opportunity to share and elevate the state of this art, made possible by the remarkable vision and efforts of my co-moderators, Er. Alpha Sheth and Prof. C. V. R. Murty.

Swaminathan Krishnan, Co-Moderator
California Institute of Technology
http://krishnan.caltech.edu[/url]












-- ­­





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PostPosted: Thu Nov 22, 2012 11:56 am    Post subject: Tall Building Design Reply with quote

dear vaishnava devi...

i appreciate your reply with full of excitement...also i don't have any doubt on your capability that you can analyse, design, build and maintain....point is not of capability but suitability of tall buildings in india....as Mr. Suraj ji has given so many points i agree with him.....also the type plant structures you have mentioned are not considered as tall structures(except few).....these plants contains facility structures/ buildings....even TG buildings mechanically don't require more than six to eight floor.......
experts can give their view point.....

sarfraj



From: "Vaishnava devi" <forum@sefindia.org>
To: econf34289@sefindia.org,  
Date: 11/22/12 11:29 AM
Subject: [E-CONF] Re: Tall Building Design



Dear Sarfraj
We do quite a lot and lot of of steel buildings in india which include process plants for petrochemical industries, PHBs for power plants, hydrocarbon processing plants for HP, indian oil ongc etc, buildings for steel plants, furnaces and many more.
A good portion of these process plant structures fall under tall buildings category which are designed by our inhouse team from gov. organisations. We refrain from using steel skeleton as a choice for residential towers only for want of skilled maintenance, apart from the cost part and its performance. We can be very sure, in near future we can see lot many steel structural buldings both high rise as well as low rise, which we are competent enough to analyse, design, build and maintain. Of late even owners of commercial complexes and corporate houses prefer steel as the material of construction with concrete deck toppings.

Regards
vaishnavadevi

From:
sarfaraj.husain [mailto:forum@sefindia.org]
Sent:
Thursday, November 22, 2012 10:28 AM
To:
econf34289@sefindia.org
Subject:
[E-CONF] Re: How should one define min stiffness requirement of tall buil



though steel buildings are not much encouraged in india........after which height it is better to go for steel building ???


sarfraj...



From: "alpa_sheth"
To: econf34289@sefindia.org (econf34289@sefindia.org),
Date: 11/19/12 11:58 PM
Subject: [E-CONF] Re: How should one define min stiffness requirement of tall buildings?



Dear Prof. Swaminathan,

You raise a very imp point re. stiffness -
Typically, we seem to link stiffness with max allowable deformation under the design seismic loads of say h/500 and up to elastoplastic inter story limit of h/120 for shear walls (say h/100 or frame-shear walls and so on) under such loads.
What has been seen in the recent New Zealand, Tohoku, Chile earthquakes is that the spectral accelerations experienced were many times more than design accelerations and conventional theories did not work. Hence defining stiffness in relation to allowable deformations in a design earthquake is problematic to me because then it no longer remains an absolute requirement but a relative one- relative to selected design earthquake.
I have seen in India some projects having a fundamental period of as high as 9 seconds for a building of just 220 to 230 m and the argument put forward is that the building is within allowable deformation/drift values so why should there be any objection.
So my question is- should we have some other way of defining stiffness- either as you say ratio of area of the shear walls/vertical elements to total floor area or max fundamental period of a building with relation to its height or ....
I'd like to hear from others regarding this issue as I think we seem to be building way too flexible buildings in India.


regards,
Alpa












On Mon, Nov 19, 2012 at 1:00 PM, krishnan_caltech forum@sefindia.org (forum@sefindia.org))> wrote: : Dear SEFIans,

I would like to welcome all members of the Structural Engineers Forum of India to this much-anticipated e-conference on Tall Building Design and Construction. The big headline from the 2010 M8.8 Maule earthquake was that of the 3000+ tall buildings (>10 stories) in Chile, 80 buildings were damaged and only one collapsed. Given the size of the event, there is a broad consensus in the global engineering community that this outcome is more than satisfactory as far as tall building performance is concerned. Much of the credit has been attributed to the building code revisions undertaken after the 1985 M7.8 Valparaiso earthquake that caused extensive damage. With few exceptions, the seismic provisions of the American Concrete Institute’s ACI-318 building code for structural concrete were adopted for the design of new reinforced concrete structures in Chile (as in India, the material of choice for tall buildings in Chile has been reinforced concrete). Damage was mostly limited to concrete crushing and spalling, and reinforcing bar buckling and fracture at the ends of thin shear walls. The shear wall boundary element detailing provisions in ACI-318 were omitted from the revised Chilean code and these thin walls lacked the required extent of confinement reinforcement. Engineers have concluded that thicker shear walls incorporating boundary elements would have prevented most of the observed damage. On the face of it, this seems to be a ratification of the ACI-318 seismic provisions and suggests that such a code could be adopted for tall building design the world over. While this may be the best course of action, this in itself may not be sufficient to produce the Chilean outcome. The ratio of wall area to floor area in Chilean tall buildings is far greater (2%-4%) than that in US tall buildings (1%-1.5%) despite the fact that they are designed nominally to the same provisions. The Chilean tall buildings are thus much stiffer than their US counterparts. The stiff Chilean tall buildings have been tested to a certain extent in this earthquake, whereas the flexible US tall buildings are yet to be tested. According to data collected by Prof. Moroni of the University of Chile, Chilean tall buildings have been getting progressively more flexible over the last 5 decades. During the same period, the damage rate in these buildings has been increasing with increasing flexibility (ref.: Prof. Jack Moehle’s EERI/PEER presentation). These observations raise important philosophical questions in the Indian context. Should Indian tall buildings go the stiff way of Chile or the flexible way of the US? How would one achieve this through the building code? I would like to see this question of “flexible vs stiff†vociferously debated in this conference. I would also like to understand and learn about the state of ductile detailing in Indian tall buildings. Do engineers and contractors recognize the importance of ductility detailing for earthquake resistance? How do we codify, implement, and regulate this? How do we educate all the stakeholders on the critical need for seismic detailing and get their “buy-inâ€? I hope to find answers to all these questions in this conference.

The Chilean example has also raised other important questions for India. The peak ground velocity in Concepcion was quite strong at 67cm/s; however, the peak ground displacement was only 21 cm. The duration of significant ground motion was quite long at 88 s, but not as much as the 1960 Chile and the 1964 Alaska earthquakes. Had the displacements and durations been greater, the outcome may have been quite different. Do we know what ground shaking would result in Delhi from a great earthquake on the Himalayan Frontal Thrust? Do we have models that can predict ground motion from such an event? I hope to find out answers to these questions in this conference. I hope similar seismological questions can be addressed for other large metropolitan cities in the northern belt and the western front including, but not limited to, Mumbai, Ahmedabad, Kolkata, Surat, Pune, Jaipur, Vadodara, and Allahabad.

I am also deeply concerned about the buildings on stilts that seem to be ubiquitous (at least in the south where I have traveled extensively in the last decade). We engineers have to come up with creative solutions to address the architectural drivers of such glaring seismic vulnerabilities without compromising structural (seismic) integrity. I hope to see creative solutions for such problems outlined in this conference. Tall first and second stories, termination and/or offsetting of gravity/lateral force resisting elements such as columns and walls, also fall in this category. I hope to see case histories of buildings with such idiosyncrasies and the novel approaches that SEFI engineers have undertaken to tackle such architecturally driven situations.

Last, but certainly not the least, environmental scientists warn us that global warming is going to result in more intense and violent storms and hurricanes in the coming decades. Our coastal cities are going to be most affected. The latest storms in the eastern US (New Jersey) and in eastern India (Chennai) are harbingers of storms to come. Are our tall buildings prepared to face these “Frankenstormsâ€? How do we deal with the moving target of wind hazard and our ever-increasing density of tall buildings in our mega-cities? During the lifetime of our building how will the wind loading patterns change with the rapidly changing landscape. How do we anticipate these changes at the design stage and build in contingencies into our designs, without being overly conservative and jacking up the costs? Seems like a pretty stiff challenge to me. I hope to hear your considered and deep thoughts on these “gray-area†questions.

In closing, I am looking forward to two weeks of exciting, rejuvenating, informative and enlightening debates and discussions on tall building design and construction in India. I sincerely hope that the SEFI community takes full advantage of this wonderful opportunity to share and elevate the state of this art, made possible by the remarkable vision and efforts of my co-moderators, Er. Alpha Sheth and Prof. C. V. R. Murty.

Swaminathan Krishnan, Co-Moderator
California Institute of Technology
http://krishnan.caltech.edu[/url]












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N. Prabhakar
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PostPosted: Thu Nov 22, 2012 2:46 pm    Post subject: Reply with quote

Dear Sefians,

The use of structural steel for tall buildings has clear-cut drawbacks on matters related to fire and heat resisitance.  The fire-rating of steel is very low as compared to that of concrete.  

For industrial type structures like factory sheds, petro-chemical plants, power plant structures, etc. open steel sections are conviniently used without having any  protection as the fire-risks are comparatively less, and also it is generally safe guarded by efficient fire-fighting systems at these locations.

But, when steel sections are used for tall buildings, they require protection all round the sections with fire and heat resisting materials.  In some western countries, there are stringent rules for  protecting steel sections.  On this matter, I would like to refer to the 9/11 collapse of World Trade Centre Towers in New York City which were framed with steel columns and steel trussed floors.  It is well known now that  the towers collapsed due to the effect of fire and heat, apart from the impact forces.  If  the towers had been built with reinforced concrete columns and floor beams, it would have taken more time to collapse, thereby reducing the casualty figures.

The scenerio in India on the matter of fire and heat resistance of steel structures  is very casual, and there seems to be no stringent rules on this matter by municipal authorities.  The general opinion is that steel is strong, but many do not know that it looses its strength drastically at high temperatures, and they do need protection.

I trust you will find theabove observation useful.

With best wishes,

N. Prabhakar
Chartered Structural Engineer
Vasai (E)
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Ambalal
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PostPosted: Thu Nov 22, 2012 4:33 pm    Post subject: Reply with quote

Respected sir's.
I would like to share a very good definition for tall building from one of the text books i am referring for my final year project..
""Tall building may be defined as one that ,because of its height ,is effected by lateral forces due wind or earthquake action to an extent that they play an important role in the structural design""..
Im following this definition. Im interested in this topic because i have choose my final year project related to tall structure using steel..
thank you
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