Twin Towers Destruction - Could it have been predicted?

I was wondering if collision simulation software was accurate enough to predict that airplanes flying into the Twin Towers with their energy release upon impact and then the combustion of the jet fuel would lead to their eventual catastrophic collapse. If the software wasn’t good enough in 2001, how about today?

When the terrorists saw the news of the towers having been hit, do you think they looked at each other and said - ok, the building’s going to collapse? Or was the collapse something that was unexpected for both us and them (them being the terrorists)?

Personally, Osama bin Laden having been a civil engineer, I wouldn’t be surprised if he had access to some really good civil engineering and CAD software…

What you’re looking for is follow-up investigation as to why the two collapsed after burning for scarcely 1 hour when engineers “thought” it could stand for 2 hours. For wooden buildings with wood posts and beams, it’s less than 30 minutes.

The method of attack was predicted by Rick Rescorla’s friend Dan Hill, according to the book The Heart of a Soldier. They were examining the destruction after the 1993 attack, and Hill came up with the idea of hijacking airplanes and flying them into the towers.

Didn’t Klebold and Harris also come up with that idea? Although I don’t think they specifically thought of the WTC.

I’m pretty sure that the method attack (or at least the possibility of a Boeing 707 colliding with the WTC) was thought up by the people building the Towers



Bin Laden did claim that they were surprised the buildings actually fell down.

Even if the software was good enough in 2001, what reason would there have been to run it? The hypothetical of, “would they have been able to predict it” seems kind of pointless.

The analysis when the buildings were designed (albeit they used a much smaller 707) showed that the structure would survive an impact. Once the building’s up and built, there’s really not much reason to re-do all the engineering work.

actually, during WW2, a B25 did in fact fly into the side of the Empire State building (in heavy fog).

The towers held up quite well to the impact energy, though it may have been enough to kill the buildings by making them too expensive to repair.

It was plenty good in 2001. It was not in the early 1960s, when the towers were designed and most “collision simulation software” required guys with slide rules making broad assumptions.

An educated layman could see that the first tower would collapse some time before it did. The terrorists were dead and in no position to make that call. :wink:

Bin Laden was a civil engineer, not a structural engineer. The fields are different enough that someone skilled in one knows little more than an educated layman about the other.

ETA: We lose sight of the fact that, in every project, we could hem and haw about every point and optimize every last detail, but there’s a point dictated by time, cost, and simply what’s possible to guard against where we need to say a Hail Mary and throw the ball. Nothing would ever get done otherwise.

the structural steel in WTC towers was coated in a heat retardant. CAD (or more precisely FEA) software is used to calculate the structural integrity of beams with this protective coating…there are also FEA calculations of beams w/o this coating…the problem with 911, was that the 757 & 767 jets impacted at 500mph, knocking the coating off the beams…as well as outright severing many of the beams altogether

There were similar high rise fires in LA & Chicago, where the buildings beams coatings worked as designed…In fact both buildings are still in use. In the Chicago fire (which was after 911) many firefighters refused to enter the skyscraper…many people slowly suffocated before the fire burned itself out.

I vaguely recall something about the WTC getting some kind of exemption allowing them to spray the fire-retardant coating onto the steel instead of applying it in the standard, more expensive way, and that supposedly the lateral impact of the aircraft caused a lot of the sprayed-on fire-retardant coating to come off the structural members. Unable to find a citation at the moment.

Nope. Jet fuel only burns at around 1,200 degrees, steel melts around 2,500 degrees. No way they could have predicted the towers would fall based on a plane crash. Had to be an inside job.

I’m not serious!

the difference between the 2 buildings is substantial. The ESB is filled with steel girders in all directions and they are encased in cement. The WTC buildings are built like a tube within a tube and the girders are encased with blown on insulation. Even at that they changed the type of insulation in the middle of the project (not blaming this but stating it for background).

It wasn’t the jet fuel that brought the buildings down. It was all the other fuel in the office that burned continuously plus the lack of insulation on the steel structure. Unlike the ESB where the concrete stayed attached to the steel the WTC’s insulation was blown off on impact.

It was a given that the buildings would collapse because there was no way to mitigate the heat from the fire. The floor joists eventually sagged and pulled the outer walls in which snapped the supports.

The steel beams only had to become annealed, not melted…annealing occurs around 500 to 1200 degrees…jet fuel can and will easily anneal, or soften, steel.

I know. I thought having “I’m not serious” starred and in italics with an exclamation point would be enough to indicate I was joking. :smiley:

The method of attack was on TV about 6 months before it happened -

Also featured prominently in Stephen King’s novel “The Running Man”.

The movie changed the ending, though.

That distinction isn’t quite as black and white as described. Some universities don’t offer a separate program in structural engineering but rather is an area of concentration of civil engineering. This was my case, I graduated with a civil engineering degree but taking all the structures courses available. Some states don’t license structural engineering as a separate discipline, some do. My state lumps all PEs together so my PE license wouldn’t indicate much about my background. If I lived in a state with a distinct SE license, that’s what I would have written the exam for.

Personally, it’s my opinion that even if bin Laden were a structural type CE, he wouldn’t have been able to model the collapses since they were a result of the fire, not the collision. Even if he had a state of the art computer model, he would also have had to have had the plans and material specifications, not to mention the time to do the modeling. Even that probably would require a lot of tweaking to model the effects of the fire.

Without knowing what the hell was going on inside I don’t know that you could have KNOWN the towers would collapse. But I think it looked rather possible. I am no structural engineer and didn’t know for sure what was going to happen, but I certainly wasn’t surprised when they collapsed; the damage sure looked like it might be catastrophic.

Because there was a gaping hole where the plane cut through multiple floors AND a fire that burned out of control, AND a gazillion tons of weight above the weakened structure.

It was just a matter of time before the steel buckled under the heat and gravity took over.