Quora.com

How did a plane crash on the upper floors of the World Trade Center result in the entire building collapsing?

That’s a legitimate question, and kudos for not just automatically declaring “ergo conspiracy”.

In fact, the damage caused by the aircraft impacting the towers — even at the high rate of speed they were traveling — was not fatal to either tower. These structures were famously designed and constructed to flex in strong gale-force winds or earthquakes, and even absorb the impact of the largest commercial aircraft at the time which was a Boeing 707 four-engine passenger jet. You can’t really tell from available video or film footage, but the initial impact caused the upper section of the structures to displace 10–20 feet from the center of gravity, and then swayed back like a pendulum. People who were up there and survived said it felt like they were going to capsize. So up to this point the buildings performed beautifully, testament to the soundness of the engineering and the redundancies in redistributing stress loads. So, what happened to cause total failure?

The fires is what happened. Ah, come on! Jet fuel doesn’t burn hot enough to melt steel. And how could a bunch of paper and office furniture burn at such high temperatures?

One needs to understand that heat causes steel to expand and warp, and lose structural strength. Think of a Japanese sword maker. He’s heating that very hard steel over a simple carbon fire. The steel hasn’t melted, but it has become softened and malleable to the extent he can fold it and hammer it, over and over.

Normally, if a fire starts in an electrical closet, it will burn everything in that immediate area and then progress to other areas. Overhead sprinkler systems and fire fighters will usually get things under control before it gets out of hand. But on 9/11, those planes were fueled for a cross-continental flight. So at the moment of impact there was a deflagration of 10,000 gallons of jet fuel which ignited large fires on 2 or 3 floors simultaneously. This is way beyond the pale in terms of manageability by fire fighters even under the best of circumstances. But in this case we have the water pipes which fed the sprinkler system severed. We have an elevator system rendered inoperative. And we have thousands of people who need to be evacuated. This was a very grave situation.

Okay, this is way up in the upper portions of the structure. How could those fires have affected lower floors? What caused them to fail?

This is so. The fires had virtually no impact on the lower 50 stories. The steel that was affected by fire was the trusses and columns in the impact zone. For Truthers who question the severity of the fires, please explain why so many people jumped to their deaths from the area above the fires. Police helicopter footage shows the perimeter columns on the floors of the impact zone bowing outward in the minutes before the collapse. The steel that was holding up all the floors above this zone was getting ready to buckle. And buckle it did. This resulted in a 25-story building falling 12 feet. That is a dynamic load the floor below cannot stand up to. Now you have a 26-story building falling onto the next floor down…and so on.

Think of it as tower of cards; you destroy the entire section of the 51st floor; the sections over them fall and add more pressure damaging the full structure and another floor goes down. It’s a chain reaction; the first floors are the ones that take longer to crumble but it accelerates as it gets more pressure and momentum from the fall.

A quick aside: there is a crucial difference in engineering and physics between a “static” load and a “dynamic” load. For example, when cars used to have robust bumpers, Car A could get behind Car B and push it forward and even push it onto the freeway and gradually speed up to 90 mph. For the most part, neither car will sustain significant damage to their bumpers. This is a static load. There is significant force applied but in a smooth way.

In a slightly different scenario Car B is stationary and Car A is travelling at 90 mph. Car A decides he’s going to push Car B again at 90 mph. But this time the moment Car A makes contact with Car B there is a horrific sound of smashing metal and the gas tank ruptures and catches fire. This is a dynamic load. Even though Car A can push Car B up to 90mph, the second scenario involves sudden acceleration.

So with the WTC towers when everything is fastened together properly, the lower floors support the weight of the upper floors. But when those upper floors undergo an acceleration, now you’re looking at a force the building was not designed to handle.

...

Quora.com

How did a plane crash on the upper floors of the World Trade Center result in the entire building collapsing?

That’s a legitimate question, and kudos for not just automatically declaring “ergo conspiracy”.

In fact, the damage caused by the aircraft impacting the towers — even at the high rate of speed they were traveling — was not fatal to either tower. These structures were famously designed and constructed to flex in strong gale-force winds or earthquakes, and even absorb the impact of the largest commercial aircraft at the time which was a Boeing 707 four-engine passenger jet. You can’t really tell from available video or film footage, but the initial impact caused the upper section of the structures to displace 10–20 feet from the center of gravity, and then swayed back like a pendulum. People who were up there and survived said it felt like they were going to capsize. So up to this point the buildings performed beautifully, testament to the soundness of the engineering and the redundancies in redistributing stress loads. So, what happened to cause total failure?

The fires is what happened. Ah, come on! Jet fuel doesn’t burn hot enough to melt steel. And how could a bunch of paper and office furniture burn at such high temperatures?

One needs to understand that heat causes steel to expand and warp, and lose structural strength. Think of a Japanese sword maker. He’s heating that very hard steel over a simple carbon fire. The steel hasn’t melted, but it has become softened and malleable to the extent he can fold it and hammer it, over and over.

Normally, if a fire starts in an electrical closet, it will burn everything in that immediate area and then progress to other areas. Overhead sprinkler systems and fire fighters will usually get things under control before it gets out of hand. But on 9/11, those planes were fueled for a cross-continental flight. So at the moment of impact there was a deflagration of 10,000 gallons of jet fuel which ignited large fires on 2 or 3 floors simultaneously. This is way beyond the pale in terms of manageability by fire fighters even under the best of circumstances. But in this case we have the water pipes which fed the sprinkler system severed. We have an elevator system rendered inoperative. And we have thousands of people who need to be evacuated. This was a very grave situation.

Okay, this is way up in the upper portions of the structure. How could those fires have affected lower floors? What caused them to fail?

This is so. The fires had virtually no impact on the lower 50 stories. The steel that was affected by fire was the trusses and columns in the impact zone. For Truthers who question the severity of the fires, please explain why so many people jumped to their deaths from the area above the fires. Police helicopter footage shows the perimeter columns on the floors of the impact zone bowing outward in the minutes before the collapse. The steel that was holding up all the floors above this zone was getting ready to buckle. And buckle it did. This resulted in a 25-story building falling 12 feet. That is a dynamic load the floor below cannot stand up to. Now you have a 26-story building falling onto the next floor down…and so on.

Think of it as tower of cards; you destroy the entire section of the 51st floor; the sections over them fall and add more pressure damaging the full structure and another floor goes down. It’s a chain reaction; the first floors are the ones that take longer to crumble but it accelerates as it gets more pressure and momentum from the fall.

A quick aside: there is a crucial difference in engineering and physics between a “static” load and a “dynamic” load. For example, when cars used to have robust bumpers, Car A could get behind Car B and push it forward and even push it onto the freeway and gradually speed up to 90 mph. For the most part, neither car will sustain significant damage to their bumpers. This is a static load. There is significant force applied but in a smooth way.

In a slightly different scenario Car B is stationary and Car A is travelling at 90 mph. Car A decides he’s going to push Car B again at 90 mph. But this time the moment Car A makes contact with Car B there is a horrific sound of smashing metal and the gas tank ruptures and catches fire. This is a dynamic load. Even though Car A can push Car B up to 90mph, the second scenario involves sudden acceleration.

So with the WTC towers when everything is fastened together properly, the lower floors support the weight of the upper floors. But when those upper floors undergo an acceleration, now you’re looking at a force the building was not designed to handle.

...

Quora.com

How did a plane crash on the upper floors of the World Trade Center result in the entire building collapsing?

That’s a legitimate question, and kudos for not just automatically declaring “ergo conspiracy”.

In fact, the damage caused by the aircraft impacting the towers — even at the high rate of speed they were traveling — was not fatal to either tower. These structures were famously designed and constructed to flex in strong gale-force winds or earthquakes, and even absorb the impact of the largest commercial aircraft at the time which was a Boeing 707 four-engine passenger jet. You can’t really tell from available video or film footage, but the initial impact caused the upper section of the structures to displace 10–20 feet from the center of gravity, and then swayed back like a pendulum. People who were up there and survived said it felt like they were going to capsize. So up to this point the buildings performed beautifully, testament to the soundness of the engineering and the redundancies in redistributing stress loads. So, what happened to cause total failure?

The fires is what happened. Ah, come on! Jet fuel doesn’t burn hot enough to melt steel. And how could a bunch of paper and office furniture burn at such high temperatures?

One needs to understand that heat causes steel to expand and warp, and lose structural strength. Think of a Japanese sword maker. He’s heating that very hard steel over a simple carbon fire. The steel hasn’t melted, but it has become softened and malleable to the extent he can fold it and hammer it, over and over.

Normally, if a fire starts in an electrical closet, it will burn everything in that immediate area and then progress to other areas. Overhead sprinkler systems and fire fighters will usually get things under control before it gets out of hand. But on 9/11, those planes were fueled for a cross-continental flight. So at the moment of impact there was a deflagration of 10,000 gallons of jet fuel which ignited large fires on 2 or 3 floors simultaneously. This is way beyond the pale in terms of manageability by fire fighters even under the best of circumstances. But in this case we have the water pipes which fed the sprinkler system severed. We have an elevator system rendered inoperative. And we have thousands of people who need to be evacuated. This was a very grave situation.

Okay, this is way up in the upper portions of the structure. How could those fires have affected lower floors? What caused them to fail?

This is so. The fires had virtually no impact on the lower 50 stories. The steel that was affected by fire was the trusses and columns in the impact zone. For Truthers who question the severity of the fires, please explain why so many people jumped to their deaths from the area above the fires. Police helicopter footage shows the perimeter columns on the floors of the impact zone bowing outward in the minutes before the collapse. The steel that was holding up all the floors above this zone was getting ready to buckle. And buckle it did. This resulted in a 25-story building falling 12 feet. That is a dynamic load the floor below cannot stand up to. Now you have a 26-story building falling onto the next floor down…and so on.

Think of it as tower of cards; you destroy the entire section of the 51st floor; the sections over them fall and add more pressure damaging the full structure and another floor goes down. It’s a chain reaction; the first floors are the ones that take longer to crumble but it accelerates as it gets more pressure and momentum from the fall.

A quick aside: there is a crucial difference in engineering and physics between a “static” load and a “dynamic” load. For example, when cars used to have robust bumpers, Car A could get behind Car B and push it forward and even push it onto the freeway and gradually speed up to 90 mph. For the most part, neither car will sustain significant damage to their bumpers. This is a static load. There is significant force applied but in a smooth way.

In a slightly different scenario Car B is stationary and Car A is travelling at 90 mph. Car A decides he’s going to push Car B again at 90 mph. But this time the moment Car A makes contact with Car B there is a horrific sound of smashing metal and the gas tank ruptures and catches fire. This is a dynamic load. Even though Car A can push Car B up to 90mph, the second scenario involves sudden acceleration.

So with the WTC towers when everything is fastened together properly, the lower floors support the weight of the upper floors. But when those upper floors undergo an acceleration, now you’re looking at a force the building was not designed to handle.

...