My memories of the day, and my opinion of the BS that is so ubiquitous on the internet regarding the collapse of the Towers.
I was on my way to work, past most of the grinding traffic when the news report came over the radio. I was on 290 just before the 610 loop. All the news report said was that a "plane" had crashed into one of the twin towers. I'm thinking daft Cessna pilot, but I happened to look out the side window at that moment at nothing in particular, and the events that followed that morning seared that image into my mind. I can see it clear as day as I type. I can vividly remember where I was when I first heard the news.
I got to work and the earlier arrivals already had a little TV set up in one of the conference rooms. I stop and watch periodically, still thinking this was accidental. The amount of fire in the live TV coverage does not look like a Cessna crash. After quite some time I stop by again to view the continuing coverage and comment to the other watchers that I don't know why that building is still standing after burning like that for so long. ( see the footnote below).
I felt like I was moving in slow motion, trying to go through the motions of my average day's work. Time seemed to drag on, and on. I stopped by the conference room again just in time to catch the second jet slamming into the second tower, and I felt like my soul drained out through my feet.
Later, it came, the collapse of the first tower, and later the second. I felt completely numb from head to foot. I have spent my life designing buildings.
And it seems that an attack like this is the only thing that will unite us as a nation to defend our constitutional right to bitch, and scratch and fight...one another.
The aforementioned footnote:
I yuk it up on the blog here. I don't write about what I do for a living, because it is of no use to 99.9% of my fellow Americans.
So, to preface my comments below, this is what I do for a living.
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My first comment is that the "Truthers" out there have no fucking idea, or knowledge of which they speak. In the interest of brevity, I'll attempt to bullet point this.
* Fireproofing on the steel columns and beams in a tower are nothing more than insulation.
* Fireproofing is designed to slow heat transfer to steel members for 3 hours for primary building columns, 3 hours for primary beams, and typically 2 hours for secondary beams.
* Fireproofing is designed to handle the heat produced by a content fire (the print of your latest report, your chair and the remnants of your left over bagel) in an office tower, not hundreds of gallons of jet fuel.
* It would require extremely unusual circumstances for a fire in an office tower to actually melt the steel structure. (think meteor strike)
* The steel in the Twin Towers did not melt. As steel is heated, it's ultimate yield strength lessens dramatically. I've seen the aftermath of a fire in a steel building that resulted in steel bar joists draped over charred chairs and desks like thirty foot long strands of spaghetti.
* Let's do some math. All we have to do is calculate this in general terms. Take a typical high rise office tower floor, in the vicinity of 22,000 square feet. Let's take an average Tower floor slab thickness of 6".
Normal weight concrete weighs 150 pounds per cubic foot. 22,000 x .5 x 150 = 1,650,000 lbs.
* Bake every steel column in hundreds of gallons of burning jet fuel on the office floor until the yield strength can no longer support 825 tons. Drop it 13.5 feet onto the floor below.
* Depending on where your are, tall buildings are designed for wind pressure, and / or seismic events. Interestingly enough, high wind pressure usually trumps seismic activity from a total load standpoint.
I digress. Tower structures are not designed to withstand the impact load from 825 tons from above.
* That is where the hypothetical math ends.
* The impact load, when the first Tower collapsed was not the weight of one floor slab. It was the weight of multiple floors, plus walls, plus curtain wall, plus all the content.
* The fire floor collapsed, and the weight and velocity increased. Then the next floor. And..so on.
* The buildings imploded themselves. I can't begin to resurrect my college physics to give a comparison on the force of the impact from 825 tons dropped from 13.5 feet, but I'm sure there would be nothing left of me.
* The "Truthers" speak of puffs of smoke on lower floors as if demolition charges had been set off. The exterior skin of an office tower only has so much vertical tolerance built into it. Best analogy is, stand up under a low beam with full thrust from your thighs..and yes you will feel it on your noggin, but it will compress a few of the vertebrae in your neck as well. (got the t-shirt)
* end of footnote. tears in my eyes.