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[Sanjay_Puranik]

I havent yet heard of an Indian code that quantifies loads due to airplane impact. We must investigate how exactly the plane fell on the building, was it a sideways collision or a vertical impact, how much of the plane really fell on the building, how much of the fire really affected the building etc. Its quite probable that most of the fuel caused
A fire on the ground and this fire didn’t affect the building.  
Long story short let us not jump to conclusions.  

From: shenoy <forum@sefindia.org>
Sent: Wednesday, June 18, 2025 11:50 AM
To: general@sefindia.org
Subject: [SEFI] Re: Amidst the gloom of the air crash, a pat on the back for hostel structural behaviour



Attention: This email was sent from someone outside the Company. Do not click links or open attachments unless you recognize the sender and know the content is safe.    

Heartfelt condolences to the near and dear who are affected by the Crash.

I do really appreciate the mention of the performance of the building structure that did not collapse , subjected to the impact and the blast. If the structure had collapsed, the death toll would have been more, definitely.

But before patting the designer and the builder for this 'unexpected’ performance of the building, I feel we need to look at this from a different point of view. We have our set procedures for the design of buildings to resist the effects of natural disasters based on our strategy of mitigation, probabilistic theories, historical evidences. In no case we design the buildings, making them disaster proof. This means saving life, giving time to vacate the invaluable life/assets, even if the building is useless after the disaster.

There is no way a building can be designed to resist a man made disaster/ unfortunate disaster like the one happened in Ahmedabad, as the forces due to impact can not be quantified in advance, nor can it be assumed, based on previous experience. So, when we pat the structural designer of this building, are we glorifying his ability to forecast the forces and design the building accordingly ? If done so, how could he assume the forces?
Does it mean the Structural designer of the building is more brainy than the structural designers of the World Trade Center which collapsed when a similar incident happened? Are we giving a message to young Structural Engineers that you start assuming huge extra loads, assuming a plane is going to fall on the building and better consider a huge factor of safety in your design? and What is the Factor of safety that will qualify for a pat if such an incident happens?

If The structure that did not collapse has been built merely satisfying the clauses of IS codes that do not suggest any quantification of the effects these kinds of impacts, I would say, our codes are very conservative.

On the other hand if the structure absorbed a part of the impact load/ blast and the saved the plane from splitting/ or saved the passengers, and if the structural designer had consciously designed the form/members/ of the building, I would definitely pat him. Otherwise, I would suspect that the building was thoroughly overdesigned, spending the owner's money, luckily that has shown some good results.

So, to earn a pat, let our young structural engineers not overdesign the buildings with loads not quantifiable, assumptions not 'justifiable', and scare the owners of probable crash of planes on their buildings ! Afterall, all buildings are not designed as shelters !

- Dr. Premanand Shenoy


alpa_sheth wrote:    
Dear Sefians,

We have had a very difficult last week seeing a terrible air crash. It makes us realise the fragility of our lives. As they say, Carpe Diem- Seize every moment of your life to do all the good that you can.

But amidst the doom and gloom I was so very pleased with the absolutely stellar performance of the Hostel building on which the Airplane fell. The building suffered a HUGE impact load, a Blast load too, because the airplane crashed on the building and through the hostel building, carrying 1.25 lakh litres of fuel which led to a huge inferno with temperatures reaching over 1000 deg C.

Despite all this, the building did not lose its integrity. No major structural vertical element (from what has been accessed over the net) collapsed and caused progressive failure of the building. The building did not collapse. Imagine the additional damage and deaths that could have been caused, if it had. Sure, the walls where the plane punched through, gave way. Some bits of slab gave way. This was the least that should have happened. But these were all localised failures. The building withstood it all, the impact, the fire without losing its load carrying capacity.

Compare this with other structures that have suffered blast impact. We're seeing a war in live action as I write this and towers are falling like ten pins in the countries at war. Also recollect another incident when two airplanes flew into two large towers in the most developed country in the world and caused a progressive failure. Not a valid comparison, I agree, but they were similar incidents.

I do not know who had designed the hostel building and who had constructed it. Both the agencies deserve to take a bow. Rarely are people celebrated for what performed well and what did not go wrong. I think it is time we acknowledged the unseen heroes.

My SALUTE to them, whoever and wherever they are!

warm regards,
Alpa Sheth

Posted via Email

[Sanjay_Puranik]

Its obvious that rear part of the fuselage has failed the perimeter beam/wall  



From: shenoy <forum@sefindia.org>
Sent: Wednesday, June 18, 2025 11:50 AM
To: general@sefindia.org
Subject: [SEFI] Re: Amidst the gloom of the air crash, a pat on the back for hostel structural behaviour



Attention: This email was sent from someone outside the Company. Do not click links or open attachments unless you recognize the sender and know the content is safe.    

Heartfelt condolences to the near and dear who are affected by the Crash.

I do really appreciate the mention of the performance of the building structure that did not collapse , subjected to the impact and the blast. If the structure had collapsed, the death toll would have been more, definitely.

But before patting the designer and the builder for this 'unexpected’ performance of the building, I feel we need to look at this from a different point of view. We have our set procedures for the design of buildings to resist the effects of natural disasters based on our strategy of mitigation, probabilistic theories, historical evidences. In no case we design the buildings, making them disaster proof. This means saving life, giving time to vacate the invaluable life/assets, even if the building is useless after the disaster.

There is no way a building can be designed to resist a man made disaster/ unfortunate disaster like the one happened in Ahmedabad, as the forces due to impact can not be quantified in advance, nor can it be assumed, based on previous experience. So, when we pat the structural designer of this building, are we glorifying his ability to forecast the forces and design the building accordingly ? If done so, how could he assume the forces?
Does it mean the Structural designer of the building is more brainy than the structural designers of the World Trade Center which collapsed when a similar incident happened? Are we giving a message to young Structural Engineers that you start assuming huge extra loads, assuming a plane is going to fall on the building and better consider a huge factor of safety in your design? and What is the Factor of safety that will qualify for a pat if such an incident happens?

If The structure that did not collapse has been built merely satisfying the clauses of IS codes that do not suggest any quantification of the effects these kinds of impacts, I would say, our codes are very conservative.

On the other hand if the structure absorbed a part of the impact load/ blast and the saved the plane from splitting/ or saved the passengers, and if the structural designer had consciously designed the form/members/ of the building, I would definitely pat him. Otherwise, I would suspect that the building was thoroughly overdesigned, spending the owner's money, luckily that has shown some good results.

So, to earn a pat, let our young structural engineers not overdesign the buildings with loads not quantifiable, assumptions not 'justifiable', and scare the owners of probable crash of planes on their buildings ! Afterall, all buildings are not designed as shelters !

- Dr. Premanand Shenoy


alpa_sheth wrote:    
Dear Sefians,

We have had a very difficult last week seeing a terrible air crash. It makes us realise the fragility of our lives. As they say, Carpe Diem- Seize every moment of your life to do all the good that you can.

But amidst the doom and gloom I was so very pleased with the absolutely stellar performance of the Hostel building on which the Airplane fell. The building suffered a HUGE impact load, a Blast load too, because the airplane crashed on the building and through the hostel building, carrying 1.25 lakh litres of fuel which led to a huge inferno with temperatures reaching over 1000 deg C.

Despite all this, the building did not lose its integrity. No major structural vertical element (from what has been accessed over the net) collapsed and caused progressive failure of the building. The building did not collapse. Imagine the additional damage and deaths that could have been caused, if it had. Sure, the walls where the plane punched through, gave way. Some bits of slab gave way. This was the least that should have happened. But these were all localised failures. The building withstood it all, the impact, the fire without losing its load carrying capacity.

Compare this with other structures that have suffered blast impact. We're seeing a war in live action as I write this and towers are falling like ten pins in the countries at war. Also recollect another incident when two airplanes flew into two large towers in the most developed country in the world and caused a progressive failure. Not a valid comparison, I agree, but they were similar incidents.

I do not know who had designed the hostel building and who had constructed it. Both the agencies deserve to take a bow. Rarely are people celebrated for what performed well and what did not go wrong. I think it is time we acknowledged the unseen heroes.

My SALUTE to them, whoever and wherever they are!

warm regards,
Alpa Sheth

Posted via Email

[vikram.jeet]

A very sad and tragic incident happened with Air India Boeing fell and dashed through Hospital Building causing humans loss ( passengers and doctors) . Whole world mourn.

As regards civil engineering aspect is concerned  , noted by Admin and  Consultant Madam Alpa

Definitely, Designers and Constructors of Building hit, in this incident , deserve  appreciation for standing to Impact of Hit and fire thereof.

However, Buildings can not be designed for any such adverse event of probability almost negligible.

Fire safety aspects of design are already covered in routine design.

Plane / missile  / ammunition attack  needs to be weighed for futuristic designs due to rapid changing war fighting scenarios, but all such needs Money, and generally these have very very low probability and may not justify in design vis a vis economics vs probability of happening .

Building near airport  zone , are always low rise - but this building was, I think few kilometers away,, but destiny

May Almighty save His Creation

Amen!

[alpa_sheth]

Dear All,

We've had some very enlightened discussions on this topic. Thanks so much, I (and I suppose all of us) have learned a lot from the  deliberations.

First of all I agree that one CANNOT (and may I add SHOULD not) consciously design for such eventualities. I am sure this building was also not designed for this air-crash event. BUT, what this building's behaviour tells us is that a building that has been designed for all the prescribed loads, that has inherent robustness, stiffness and integrity,   and has been detailed well has redundancies we are not even aware of!!

This reminds me of the behaviour of thousands and thousands of buildings in Ahmedabad built in the 1970s and earlier which were not designed for the shaking of Jan 26 2001 earthquake. And yet they behaved superbly, with just some minor non-structural separation cracks at masonry wall-beam junctions. I happen to have one such apartment in Ahmedabad,  so I speak from first-hand experience. My father was the designer of that 7 storey tower and he candidly told me that there was no concept of  "ductile design" at that time.   The  earthquake codes were nascent (First earthquake code was in 1962 I think). But simple rectangular configurations,  no stilts, no floating columns, no gymnastics  and the buildings could take the shaking in their stride.

The points I was trying to make in my earlier mail were:

a) Concrete seems to behave  much better under impact,  heat and  fire than steel.  I'm not really sure about all the fireproof paint, vermiculite  etc we provide on steel and imagine its just as good as solid concrete.  

b) A building with inherent stiffness, continuous load path, robustness and integrity generally behaves better  under ALL types of loads, incl.  impact and blast loads which it may actually not have been designed for.  So, there is no shortcut to these basic principles.

c) And ofcourse we can never ever forget the element of luck. Not a scientific statement, but a truism nonetheless. As earthquake engineers say this again and again, just because your building withstood an earthquake does not ensure it will withstand the next one!!

With warm regards,
Alpa

[vikram.jeet]

Very aptly analysed by Madam Alpa Sheth ,,
Steel buildings are more prone to Impact compared to Rcc buildings,,
Steel high rise could not withstand 9/11 attack,, and rising temperature s due to Massive fires made the structure worst to stand.

Luck factor is always there in any situation ,,  

But , definitely  ,appreciate Madam  Alpa for,  ALSO  ,seeing beyond the lines in present case on civil / structure Aspect confronted with Aeroplane mishap.

With kind regards

Vikramjeet


[quote="alpa_sheth"]Dear All,

We've had some very enlightened discussions on this topic. Thanks so much, I (and I suppose all of us) have learned a lot from the  deliberations.

First of all I agree that one CANNOT (and may I add SHOULD not) consciously design for such eventualities. I am sure this building was also not designed for this air-crash event. BUT, what this building's behaviour tells us is that a building that has been designed for all the prescribed loads, that has inherent robustness, stiffness and integrity,   and has been detailed well has redundancies we are not even aware of!!

This reminds me of the behaviour of thousands and thousands of buildings in Ahmedabad built in the 1970s and earlier which were not designed for the shaking of Jan 26 2001 earthquake. And yet they behaved superbly, with just some minor non-structural separation cracks at masonry wall-beam junctions. I happen to have one such apartment in Ahmedabad,  so I speak from first-hand experience. My father was the designer of that 7 storey tower and he candidly told me that there was no concept of  "ductile design" at that time.   The  earthquake codes were nascent (First earthquake code was in 1962 I think). But simple rectangular configurations,  no stilts, no floating columns, no gymnastics  and the buildings could take the shaking in their stride.

The points I was trying to make in my earlier mail were:

a) Concrete seems to behave  much better under impact,  heat and  fire than steel.  I'm not really sure about all the fireproof paint, vermiculite  etc we provide on steel and imagine its just as good as solid concrete.  

b) A building with inherent stiffness, continuous load path, robustness and integrity generally behaves better  under ALL types of loads, incl.  impact and blast loads which it may actually not have been designed for.  So, there is no shortcut to these basic principles.

c) And ofcourse we can never ever forget the element of luck. Not a scientific statement, but a truism nonetheless. As earthquake engineers say this again and again, just because your building withstood an earthquake does not ensure it will withstand the next one!!

With warm regards,
Alpa

[Dr. N. Subramanian]

Dear Er Alpa,

Thank you for your observation of the building on which the Air India Plane fell. I was also wondering how the building withstood the shock, as the flight was going to London and hence was having lot of fuel. Thus the impact would have been similar to the one that happened in the Twin WTC towers of New York.

I am sure that the designers might not have considered the impact load due to any plane crash. I suspect that the fire and blast happened outside the building, as the lone person who miraculously escaped said that all the dead bodies of people were lying around him on the ground.

As our Er. Alok Bhowmick has said someone near the blast should inspect and inform us more details about the building, in order that we may come to a conclusion.

Anyway, once again thank you for analysing the crash from the point of view of structural engineering.

Warm regards
Subramanian

[Sanjay_Puranik]

All said and done, the building survived with minimal damage after having been subjected to loads that were not considered during its design
Now how severe these loads were, where they got applied is a matter of guesswork. Had the impact been on the façade , I doubt if it would have escaped with the  
Little damage that it did. Whatever pictures we see of the building don’t show fire damage. I think a part of main body (tail section as the pics show) fell on the building  
And DID cause damage. The wings and forward section fell elsewhere. Also the building was spared of the huge fireball as the wings (where most of the fuel is stored) containing the highly inflammable fuel Fell elsewhere

From: Dr. N. Subramanian <forum@sefindia.org>
Sent: Thursday, June 26, 2025 11:53 PM
To: general@sefindia.org
Subject: [SEFI] Re: Amidst the gloom of the air crash, a pat on the back for hostel structural behaviour



Attention: This email was sent from someone outside the Company. Do not click links or open attachments unless you recognize the sender and know the content is safe.    

Dear Er Alpa,

Thank you for your observation of the building on which the Air India Plane fell. I was also wondering how the building withstood the shock, as the flight was going to London and hence was having lot of fuel. Thus the impact would have been similar to the one that happened in the Twin WTC towers of New York.

I am sure that the designers might not have considered the impact load due to any plane crash. I suspect that the fire and blast happened outside the building, as the lone person who miraculously escaped said that all the dead bodies of people were lying around him on the ground.

As our Er. Alok Bhowmick has said someone near the blast should inspect and inform us more details about the building, in order that we may come to a conclusion.

Anyway, once again thank you for analysing the crash from the point of view of structural engineering.

Warm regards
Subramanian       
alpa_sheth wrote:    
Dear Sefians,

We have had a very difficult last week seeing a terrible air crash. It makes us realise the fragility of our lives. As they say, Carpe Diem- Seize every moment of your life to do all the good that you can.

But amidst the doom and gloom I was so very pleased with the absolutely stellar performance of the Hostel building on which the Airplane fell. The building suffered a HUGE impact load, a Blast load too, because the airplane crashed on the building and through the hostel building, carrying 1.25 lakh litres of fuel which led to a huge inferno with temperatures reaching over 1000 deg C.

Despite all this, the building did not lose its integrity. No major structural vertical element (from what has been accessed over the net) collapsed and caused progressive failure of the building. The building did not collapse. Imagine the additional damage and deaths that could have been caused, if it had. Sure, the walls where the plane punched through, gave way. Some bits of slab gave way. This was the least that should have happened. But these were all localised failures. The building withstood it all, the impact, the fire without losing its load carrying capacity.

Compare this with other structures that have suffered blast impact. We're seeing a war in live action as I write this and towers are falling like ten pins in the countries at war. Also recollect another incident when two airplanes flew into two large towers in the most developed country in the world and caused a progressive failure. Not a valid comparison, I agree, but they were similar incidents.

I do not know who had designed the hostel building and who had constructed it. Both the agencies deserve to take a bow. Rarely are people celebrated for what performed well and what did not go wrong. I think it is time we acknowledged the unseen heroes.

My SALUTE to them, whoever and wherever they are!

warm regards,
Alpa Sheth

Posted via Email