Total Building Collapse from a Single Column Failure

[Africanus]

The so called load redistribution is the key concept here.

NIST listed three phenomena that lead to buckling of columns 80 and 81:

• load redistribution
• increasing unsupported length
• damage columns by falling debris

See NCSTAR 1A, p. 22.

 

[erwinl]

Have a look at the roof of 7WTC. Do you think a single column supported the EPH?

You don't see how the TT#1 and TT#2 could have been and probably WERE involved in collapse of the EPH and the collapse of TT#3 was involved in the WPH?

I know you can't see it so it didn't happen... right?

I see what you mean. I mistook you for a thruther. Apologies for that.

To my eyes though. If you look at the collapse of WTC7, it seems that the part of the east penthouse above column 79 is the first to disappear.
Wouldn't it be different if the start was with TT1 and/or TT2? Or do I understand you wrong?

 

[ozeco41]

Sander the sad aspect of these posts is that you get so tantalisingly close to seeing the real priorities.

Let me cut out all the blame and angst material and focus on how close you do get.

I've stated that I feel the AFTER incident reports appear to avoid assigning any responsibility to engineering "features" which failed to perform as expected. The engineering work done years before may have been adequate, legal in that it met or exceeded minimum regulatory requirements.... but the point is that once the ◊◊◊◊ hit the fan we now know that both regulatory and engineering "professionals" failed to protect the public and property. We're supposed to learn how to make safer structures from these events.

Emphasis is on LEARN and I have put it in DarkRed to see if it makes you realise what you just wrote.

Learn - a process of getting better as a result of applying the lessons of experiences we have - LEARNING from experience. It should mean that the next time it happens we will be better at dealing with it. It does not mean what you imply - that every possible thing that could go wrong is identified by geniuses who accurately predict every possible event before it is experienced. Nor does it mean witch hunts of blame castigating those who do their job properly but get it wrong because new factors arise.

You continue to support the obnoxious claim that we should change the rules then go back in time to sanction people on the basis of changed rules. You won't even acknowledge that the concept is offensive. However - remember YOU said LEARN and that is a step forward even if you have not yet realised what you said..

9/11 was supposed to produce recommendations to mitigate such disasters in the future. Fine. Did you see anything about the nature of field connections or use of long span bar joists or building over a power station or forbidding the storage of fuel in next to a power station?...

Sander you are an architect. What are the primary design considerations for buildings in the event of fire? What is a primary consideration if the building is steel framed? Do you as an architect refuse to use steel frames?

What are those priorities:
1) Protect the building OR protect the people?
2) Recognise that steel frames are vulnerable to heat OR like lying truthers pretend that steel is not susceptible to failure in fire?

You of all people posting here should know that design for steel buildings is based around recognising the risks of fire and delaying the effects of fire until the people can escape AND/OR the fire is brought under control.

You of all professions should get the priority right. Yet you dismiss these:

What were the recs? Improved fire protection? Properly encased emergency egress...

Shame Sander denigrating those two. They should be the top two priorities. Most of those ~3000 people died because they could not "egress" those buildings. Despite all your misfocussed attention the buildings stood long enough for many more to get out despite a scale of attack that was outside reasonable expectations for the 1970s and despite your earnest use of 20/20 hindsight to assessing blame. The problem was first a lack of protected egress. Then failed fire fighting - vulnerable to single point failure.

That's it? Those are the sum total of the lessons learned????

Don't be ridiculous. You cannot prevent those who design tall buildings from learning the lessons.

So you want stronger buildings. How much stronger??? The collapses at WTC were not expected by the perpetrators - an unexpected "bonus" for their evil acts. But, if at some future time a similar attack is planned, can you as an architect build a building strong enough to resist the probably more massive attack? It wont be one single airplane unassisted by explosive devices if ever there is a next time. Would your focus be "Protect the People" OR "Protect the Building"?

The reasonable prudent professional designing a high rise will look first to providing secure egress for the people in the event of fire and major damage. To multiple redundancy of fire fighting measures primarily to ensure time for escape of the occupants. He may look at progressive collapse resistance but the priority will remain protect the people #1 protect the building a distant #2. Despite anyone's efforts to reverse those priorities.

 

[JSanderO]

Sander the sad aspect of these posts is that you get so tantalisingly close to seeing the real priorities.

...

The reasonable prudent professional designing a high rise will look first to providing secure egress for the people in the event of fire and major damage. To multiple redundancy of fire fighting measures primarily to ensure time for escape of the occupants. He may look at progressive collapse resistance but the priority will remain protect the people #1 protect the building a distant #2. Despite anyone's efforts to reverse those priorities.

Ozzie,

I am not going to cut and snip your post and respond to each idea and sentence.

You miss the trust of what I am trying to achieve. What the authorities armed with the proper understanding of what happened to those towers choose to do is a separate issue. I am not a lawyer and I won't go there.

What we got were some weak (IMO) recommendations for fire protection. We probably need more stringent ones. Apparently the EU has a tougher standard.

There were also design, planning, erection decisions which APPEAR to have assisted in the total collapse. MAYBE. This was not discussed and there was no LEARNING about the decisions which ROOSD and TTF point to. Did the engineers and planners get the message without it being explicitly stated? Dunno. Should it have been explicitly stated? I think so.

I began this all to understand (learn) why these towers collapsed as they did. Heat is only the most general cause. I want more specificity. YOU don't. More specificity gets to the PLANNING decisions.

That is my point.

I've satisfied my own curiosity... without too much help from NIST.

 

[jaydeehess]

Have a look at the roof of 7WTC. Do you think a single column supported the EPH?

No, that is not what I asked. I asked why the hole opened up at the location of col 79 FIRST. The hole into which the EPH drops does not open up all at once and swallow the structure whole. It opens at a corner, widens and the EPH tilts into it. It starts at the location of col 79 , not at the location of 73/76 which are directly resting on TT1. IF TT1 failed FIRST then the effect at the rooftop would be seen at the location of 73/76 FIRST. Although I have asked about this several times you simply refuse to address it.

You don't see how the TT#1 and TT#2 could have been and probably WERE involved in collapse of the EPH and the collapse of TT#3 was involved in the WPH?

Nope did not say that. What I was saying is laid out in the paragraph directly above.

I know you can't see it so it didn't happen... right?

I am giving you every chance to convince me that you are correct. Years back I argued that the consideration of diesel fuel fires in the WTC 7 interim report was justified because of a few facts, that not all of the fuel was accounted for and the simple presence of a fuel system in a key structural area. You have not deigned to address my problems with your TT1 first failure theory.

Although FEMA had already concluded that there was no evidence of such fires I defended the practise that NIST do their own independant study of that issue. I was told I was an apologist for NIST who was only putting this theory forth in order to hide the truth. NIST looked for evidence of such fires and found none, as FEMA before them. That's two orgs that have come to the same conclusion. My take is that this settles the issue. Yours seems to be that both are lieing in one way or another in order to suppress any finding of blame on the part of the engineering that allowed gensets and fuel in the building.
That is an example of a conspiracy theory JSO. Convince me otherwise and/or convince me that there was such a fire.

So two things then, explain why hole at roof starts to open at location of col 79, and show that TT1 was under attack by fire. Those two factors need to be addressed in order to convince anyone that your hypothesis may be correct.

 

[chrismohr]

I wish I could remember a long conversation I had with Michael Newman at NIST about the safety recommendations NIST proposed which were quickly implemented by many fire codes worldwide. And can someone tell me about the new building in Asia that burned for several hours without collapsing? Credit was given to the fact that this new building was constructed under the new NIST guidelines such as no long-span trusses. Other recommendations: wider staircases so firefighters can go up while occupants go down; better reinforcement for protection of the people in the stairwells; elevators that possibly can safely function during a fire; avoiding long-span trusses. In fact, Michael told me he had just gotten off the phone with an architect who was complaining to him that the NIST recommendations were unnecessary and too expensive! Which BTW is exactly what Richard Gage said to me in our debate. I asked him, if you think the NIST Report is so bad, do you think the safety recommendations it proposed post 9/11 were a waste of money, since the buildings should never have come down in the first place? He said yes, they were a waste of money. Then why, I asked, do we put fireproofing around the steel structual elements? Gage: To make them indestructible in fire! Well, that's very scary, I said, because I consider the lives of the people in this room to be well worth the cost of implementing NIST's safety recommendations.

None of this is to imply that I have the knowledge to support the NIST safety recommendations as they stand. Maybe you are right and they are not enough. But from what I've seen, they are not too bad.

The one area I've always wondered about, which you bring up, is the choice to allow massive amounts of diesel fuel in the lower floors of a high-rise. Even if NIST is right that these huge tanks did not significantly contribute to bringing down Building 7, it certainly gives me pause that a raging unfought fire engulfed a huge building that had so much fuel in it. I wouldn't want to jail the original designers, but if the observation that a huge supply of diesel fuel was in a building that caught fire is not included in the NIST recommendations, that seems like an oversight of something obvious to me.

 

[JSanderO]

No, that is not what I asked. I asked why the hole opened up at the location of col 79 FIRST. The hole into which the EPH drops does not open up all at once and swallow the structure whole. It opens at a corner, widens and the EPH tilts into it. It starts at the location of col 79 , not at the location of 73/76 which are directly resting on TT1. IF TT1 failed FIRST then the effect at the rooftop would be seen at the location of 73/76 FIRST. Although I have asked about this several times you simply refuse to address it.

Nope did not say that. I was saying,,,, read the paragraph directly above.


I am giving you every chance to convince me that you are correct. You have not deigned to address my problems with your TT1 first failure theory.

If you look at the diagram the EPH is over the entire East side load transfer region and col 79 is almost in east and north of center of the EPH. The EPH seems to have its roof fold in approximately where the N-S line of the bream connection 79-80 and 81. Hard to tell though.

One column (point) failure (79) would not produce the motion seen. One line would.

So you agree?

 

[jaydeehess]

If you look at the diagram the EPH is over the entire East side load transfer region and col 79 is almost in east and north of center of the EPH. The EPH seems to have its roof fold in approximately where the N-S line of the bream connection 79-80 and 81. Hard to tell though.

One column (point) failure (79) would not produce the motion seen. One line would.

So you agree?

I see that the analysis done by NIST for several different column failure scenarios best matches what was observed for a col 79 failure, not a col 73, 76 failure.

A 79, 80 ,81 failure at roof level does not indicate a TT1 (and thus col 73&76) at fifth floor initial failure.

 

[DGM]

So two things then, explain why hole at roof starts to open at location of col 79, and show that TT1 was under attack by fire. Those two factors need to be addressed in order to convince anyone that your hypothesis may be correct.

Another issue was, TT1 and TT2 were not located in the same space as the generators or electrical vaults. They were in a ventilation and A/C area that was separated by masonry walls with little combustible material available.

 

[JSanderO]

Another issue was, TT1 and TT2 were not located in the same space as the generators or electrical vaults. They were in a ventilation and A/C area that was separated by masonry walls with little combustible material available.

There were 2 explosions I recall.

 

[DGM]

There were 2 explosions I recall.

And? How long after did the building collapse?

 

[JSanderO]

And? How long after did the building collapse?

The explosions were not THE cause of the collapse, but they were contributory to the progression of weakening and failures.

Are you confused by the fact that there was a PROGRESSION of failures, each of which occurred when a sub system's capacity was exceeded...

The progression cascaded and went "runway" as cascading system failures do... when the reserve capacity of the system was consumed... and then the next stress increase tipped the system passed stability into instability and on to global collapse.

 

[DGM]

The explosions were not THE cause of the collapse, but they were contributory to the progression of weakening and failures.

Are you confused by the fact that there was a PROGRESSION of failures, each of which occurred when a sub system's capacity was exceeded...

The progression cascaded and went "runway" as cascading system failures do... when the reserve capacity of the system was consumed... and then the next stress increase tipped the system passed stability into instability and on to global collapse.

I'm not confused at all. I'm asking for your evidence of conditions that were right to cause the failure where you suggest.

 

[JSanderO]

DGM...

I wasn't there.. Nor was NIST... nor was anyone else for the entire day... nor were they at column 79 on floor 13...

Correct or not?

Solving this mystery explaining collapse requires we INFER some things. I don't think there is a lot of hard evidence to work with. We have:

structural plans
architectural plans
vids of building movements
pics of the building
anecdotal witness reports
testing of some recovered materials (don't know which or what they showed)
seismic record (may not tell much)
some temp data (I think) of the face of the building not of the inside
Con Ed report (loss of feeders)
expert assessments (Cantor, ASCE, Chief of FDNY etc.)

I connected the dots which stood out to me. I can't prove anything. Nor can NIST. Nor can you! (or Ozzie)

 

[jaydeehess]

Solving this mystery explaining collapse requires we INFER some things. I don't think there is a lot of hard evidence to work with. :

We have:
structural plans
architectural plans

Yes and those plans are used by all concerned

vids of building movements
pics of the building

Again used by all concerned

anecdotal witness reports

Including those of trained fire fighters who reported no fires on lower floors nor a smell of fuel leaking.

There are conflicting reports concerning an explosion in WTC 7 in the Con-Ed station. Which at any rate would not affect any scenario wrt collapse.

There is one set of report of an explosion in 7WTC between the collapses of WTC 1 & 2, by Jennings and Hess. There is no confirmation of this explosion(no reports from outside afaik)
There are exactly no reports of fires by anyone, on the 5-6th levels at any time.

expert assessments (Cantor, ASCE, Chief of FDNY etc.)

FEMA, NIST

I connected the dots which stood out to me. I can't prove anything. Nor can NIST. Nor can you! (or Ozzie)

Nor can I. However if I am going to connect dots leading to acceptance of your hypothesis, I am going to need a few more than you have outlined. The dots indicating that first failure was of TT1 are simply not there for me to draw a line through.

Sorry Sander, NIST's hypothesis may be flawed but , imho, not as much so as the one you propose.

 

[DGM]

I connected the dots which stood out to me. I can't prove anything. Nor can NIST. Nor can you! (or Ozzie)

I understand but, you are the one that is alleging criminal behavior. Wouldn't you want a little more to go on before you go to that point?

 

[JSanderO]

I understand but, you are the one that is alleging criminal behavior. Wouldn't you want a little more to go on before you go to that point?

I did not allege criminal behavior. I suggested some questionable decisions were made by planners, developers, Con Ed, engineers, the Mayor's office and so forth which seem to play a contributory role in the collapse.

None of this was brought out. NIST coulda... perhaps shoulda.

That I find odd.

 

[jaydeehess]

I did not allege criminal behavior. I suggested some questionable decisions were made by planners, developers, Con Ed, engineers, the Mayor's office and so forth which seem to play a contributory role in the collapse.

None of this was brought out. NIST coulda... perhaps shoulda.

That I find odd.

Odd, perhaps. Shoulda , yes IMHO.
Quintere also was frustrated that NIST chose not to condemn certain aspects regarding fire safety, the special fire codes for the PA, the fire stairs in the towers being in the center and using only drywall fire separation, non-cementatious steel fire 'proofing'.
Instead of assigning any blame for decisions made decades prior, NIST chose to concentrate on recommendations.
You say you wanted to see construction recommendations but if one recommendation was no long span trusses then you got at least one. Iirc there was also a recommendationfor diagonal bracing between floors wwhich the towers did not have

One factor you seem especially concerned about is storing fuel for generators in the building. However the idea that this had any play in any 9/11 collapse has not been illustrated and therefore NIST would be stretching things to try and include that in any recommendations arising from the 9/11 collapses. The reason this is not included in the recommendations is not because NIST wants to make life easy of engineers, or to cover for a bad design decision, it is because it cannot be shown to have been a factor in the collapse.

 

[Newtons Bit]

I did not allege criminal behavior. I suggested some questionable decisions were made by planners, developers, Con Ed, engineers, the Mayor's office and so forth which seem to play a contributory role in the collapse.

None of this was brought out. NIST coulda... perhaps shoulda.

That I find odd.

NIST recommended that buildings be designed for a "burn-out" scenario. This was ruled as an unnecessary expense by the Code Committees. It's really no surprise, as it is a level of analysis that would probably result in doubling the structural engineers fee and provide additional protection that the vast majority of structures will never need.

Structural Engineering, amongst many other things, is about balancing risk with cost. We do not design buildings to be invincible. We set limits. For example, we design buildings for design seismic and wind events that do not correspond with theoretical maximums. Seismic hazards typically refer to a 5% chance of exceedence over a 50 year period (though more important buildings have a lower rate). Wind hazards are similar.

There is a built-in probability of collapse for every building for every type of hazard. Given that planes ramming an adjacent building, causing it to collapse and showering a lower structure with burning debris is a very rare event to design a typical building for, we don't want to do it. And that's okay.

 

[carlitos]

BUT we will never know and why should it interest anyone?

Counting the number of angels dancing on the head of a pin.