Can Skyscrapers Fall Over on Their Side?

[Thomas B]

Your quote shows the fire chief had the area evacuated 3 hours before the building collapsed; I fail to see what additional "urgency" could have achieved here.

Apparently it would have allowed rescue crews at WTC6 and WTC1 to continue working.

The order [to evacuate] terminated the ongoing rescue operations at WTC 6 and on the rubble pile of WTC 1. (p. 111)

https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-8v1.pdf

 

[econ41]

Who knows if they could have used Hudson River water to replenish the sprinkler system???

As a suitably qualified engineer I would say it was highly probable. Whether it was capable of providing the quantity I cannot guess. Remember distance (horizontal) hose capacity, pumping capacity both H and Q... 47 storeys is a significant lift. Nothing compared with 110. I've often mused as to all the presumptions that it would be an easy, routine job to supply water for firefighting at EITHER 47 or 110 storeys. There is significant high-pressure issue limitations and I have no idea how well equipped the NY firefighters are. Obviously, there was no time for emergency large scale pumping at the Twin Towers. And don't be deceived by the apparent 7 hours for WTC7. It was unsafe to enter long before the collapse. Physical logistics may have been possible for pumping the Hudson. The time available certainly wasn't.

 

[econ41]

And the fire chief made his decision considering them and their effectiveness.

That is the bottom line. The decision was made. And no one AFAIK has ever made a valid criticism of what was the appropriate command decision. Emergency decisions have to be made in real time. NOT 20 years later with half-informed 5/20 hindsight.

Which means your call for "urgency" falls flat yet again.
Your quote shows the fire chief had the area evacuated 3 hours before the building collapsed; I fail to see what additional "urgency" could have achieved here.

It wouldn't change the argument if WTC7 had survived 15 hours before the collapse.

 

[Thomas B]

It wouldn't change the argument if WTC7 had survived 15 hours before the collapse.

Can you say a bit more about why this wouldn't matter?

Presumably, those 15 hours would have been spent continuing to monitor the situation, evaluating options, and seeking creative solutions. Since we know the key factor was the fire situation around column 79, if the building had lasted longer it would have been because the fire hadn't got there yet, or because it passed before the girder had completely walked off.

After the 1993, bombing, for example, there was great urgency about bracing the columns laterally (and even leaving debris in place that was doing this until braces could be put in place).

Depending on the fire situation in WTC7 after 15 hours, I imagine efforts to mitigate a total collapse would start to look viable.

 

[econ41]

Can you say a bit more about why this wouldn't matter?

No. It would be pointless.

Presumably, those 15 hours would have been spent continuing to monitor the situation, evaluating options, and seeking creative solutions. Since we know the key factor was the fire situation around column 79, if the building had lasted longer it would have been because the fire hadn't got there yet, or because it passed before the girder had completely walked off.

After the 1993, bombing, for example, there was great urgency about bracing the columns laterally (and even leaving debris in place that was doing this until braces could be put in place).

The WTC 9/11 events were a major emergency managed in real time. A situation where the Commander at every stage needs to make decisions in real time without the benefit of amateur ill-informed criticism 20plus years later.

Try putting yourself in the place of that real-time decision-making manager.

He took the decision to not progress acive fire fighting at a time. He did not know with assurance that the building would in fact collapse. That is NOT the decision criteria. The decision was based on the probability of collapse. The plausible possibility. The decision was taken and was valid at the time. (IF you can prove it was not valid we can discuss your proof.) The decision would still have been correct even if the building did not collapse. Put yourself in his seat AT THE TIME. You are implicitly including factors that are only known in hindsight and confusing your reasoning.

Depending on the fire situation in WTC7 after 15 hours, I imagine efforts to mitigate a total collapse would start to look viable.

And, if the building was still standing three days later and the fire had exhausted itself....So bleeding what! We are discussing the reasonable basis of operational decision making with two extreme outcomes viz (i) Buiding collapsed; and (ii) Building didn't collapse. BOTH outcomes are consistent with what I have presented. Both are in the scope of the Emergency Managers' decision. No way would he be giving attention to recovery whilst rescue was the primary objective. Recovery and possible refurbishment of a surviving building is not in the scope of ur discussion. (or even demolition as a commercial "write off")

 

[Thomas B]

Put yourself in his seat AT THE TIME. You are implicitly including factors that are only known in hindsight and confusing your reasoning.

No, it was you who gave him an extra 10 hours. I was trying to put myself in this different, counterfactual situation.

 

[econ41]

No, it was you who gave him an extra 10 hours. I was trying to put myself in this different, counterfactual situation.

I said: "Put yourself in his seat AT THE TIME." Please do try to respond to what is put to you.

 

[Thomas B]

No way would he be giving attention to recovery whilst rescue was the primary objective.

I'm not suggesting recovery of the building was a primary objective. I'm just suggesting that preventing a building from collapse might be a goal in itself since such an event is surely dangerous and, as in this case, disruptive to the ongoing rescue operations in the vicinity.

At about 2:30 they had weighed their options and decided to abandon rescue operations in and near WTC7 and any attempt to fight the fires. You say they couldn't have been sure it would collapse. If you're right, then I guess they were in part hoping the danger would pass.

And, if the building was still standing three days later and the fire had exhausted itself....

At that point, they'd be left in the 1993 post-bombing situation of having to temporarily brace exposed columns until a plan for recovery or demolition could be made.

I doubt they could have known for sure already at 2:30 PM on 9/11 that they building was a write-off. And I doubt that they would have continued to keep their distance 15 hours or three days later, still just waiting for it to collapse on its own. That is surely something they'd like to be in control of.

Remember, the question in this thread is how certain they could be about how the building would collapse if it did.

 

[econ41]

I'm not suggesting recovery of the building was a primary objective. I'm just suggesting that preventing a building from collapse might be a goal in itself since such an event is surely dangerous and, as in this case, disruptive to the ongoing rescue operations in the vicinity.

The primary goal of fire operations is to prevent or minimise loss of life, Protecting the building is always secondary. And "recovery" is a sub-set of "protecting the building". And disruption of nearby rescue operations was a factor to be weighed in balance - it is actually a factor arising as a side effect of the decision about the greater potential dangers associated with continuing WTC 7 active fire-fighting

At about 2:30 they had weighed their options and decided to abandon rescue operations in and near WTC7 and any attempt to fight the fires.

Keep the factors in their correct relationships. They made the big decision to discontinue active fire fighting at WTC7. There were no rescue operations at WTC7. The lesser rescue operations on other buildings were necessarily ceased/reduced in scope as a consequence of the main decision..

You say they couldn't have been sure it would collapse. If you're right, then I guess they were in part hoping the danger would pass.

Wrong-way round argument. They couldn't be sure it wouldn't collapse was the correct basis for the decision. Yes, they may have been "hoping" but secondary - subordinate to the decision taken.

At that point, they'd be left in the 1993 post-bombing situation of having to temporarily brace exposed columns until a plan for recovery or demolition could be made.

I doubt they could have known for sure already at 2:30 PM on 9/11 that they building was a write-off. And I doubt that they would have continued to keep their distance 15 hours or three days later, still just waiting for it to collapse on its own. That is surely something they'd like to be in control of.

Reasonable speculations but way off both the topic we are discussing and any logical conclusions we could reach if we discussed the "WTC7 did not collapse" scenarios

Remember, the question in this thread is how certain they could be about how the building would collapse if it did.

Actually, the real thread topic is "Can Skyscrapers Fall Over on Their Side?" and none of our discussions is directly related to that topic.

 

[Mendel]

It wouldn't change the argument if WTC7 had survived 15 hours before the collapse.

If the building had fallen over 10 minutes after it had been evacuated, I think it'd be fair to say that some more urgency would've been advisable. 3 hours means the order was given well in time.

 

[Mendel]

I doubt they could have known for sure already at 2:30 PM on 9/11 that they building was a write-off.

I don't doubt they knew that

the building had suffered structural damage from falling debris, extensive fire damage, water damage from the upper floor sprinklers, and pervasive smoke damage. I would not be surprised if it was deemed a write-off at that point—unsaveable, to be torn down even if it hadn't collapsed.

you agreed to this

 

[econ41]

If the building had fallen over 10 minutes after it had been evacuated, I think it'd be fair to say that some more urgency would've been advisable. 3 hours means the order was given well in time.

Agreed for the rate of deterioration >> length of delay before collapse as was observed on 9/11.

Given that occupants of the building had escaped the relevant urgency was getting the fire and rescue workers clear before any likely collapse. Given that the decision was made 3 hours before the collapse indicates that a level of "playing safe" caution was exercised. But the on-site commanders had neither foresight nor the 20/20 hindsight available to us "armchair critics" 20+ years later. The "call was right on the day" is probably as much as we can say.

 

[Mendel]

Given that occupants of the building had escaped the relevant urgency was getting the fire and rescue workers clear before any likely collapse.

Exactly. And that objective was comfortably achieved.