Post ATLfF8R18tqnhCmLdQ by InkomTech@infosec.exchange
(DIR) More posts by InkomTech@infosec.exchange
(DIR) Post #ATJWGC35u2wFI66BwO by lauren@mastodon.laurenweinstein.org
2023-03-05T18:34:21Z
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In the early 1970s on a visit to New York City for a conference, I took the express elevator in one of the original World Trade Center towers up to the observation level just below the roof. The towers were brand new, and what would be a massive antenna array on the other tower was still under construction. This was my first and only visit to the towers.Roof access was not permitted that day due to high winds, so I walked around the observation floor looking through the narrow windows between the outer structural frame, at NYC spread beneath me. The glass of the windows had little outline decals identifying various of the landmarks.Suddenly an alarm went off and everyone was startled. When I looked behind me I saw that access to the elevators was gone -- a massive steel fire door had dropped from the ceiling completely blocking the way we had entered. Nobody knew what was going on, or how to exit safely via stairways. There was no panic per se, but a lot of very concerned people. Including me.After some period of time that seemed like forever but probably was only 10 minutes or so, firemen appeared -- it had been a false alarm -- they raised the fire door, and we could leave.At the time, I noted to my companion how unorganized the situation seemed. What if this had been an actual fire?I also made one other comment at the time. I said that the design of the building, with no internal supporting pillars and just the central core and outer framework holding it up, seemed odd to me. What would happen, I said, if something significantly damaged the outer frame? What would stop the entire building from collapsing like [vinyl] records on a record changer?Those words have haunted me to this day. -L
(DIR) Post #ATJYpfPytuvcQBqZm4 by zzzeek@fosstodon.org
2023-03-05T19:03:07Z
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@lauren I worked in that building for awhile and it always freaked me out how giant and not too ready for emergencies it seemed
(DIR) Post #ATJbXoYySdTTQzESe0 by tknarr@mstdn.social
2023-03-05T19:33:29Z
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@lauren 1/ They thought about the problem of damage to the exterior framework when they designed the towers. The biggest thing they did to address it was design that framework so it transferred load laterally around damaged portions. It worked well, considering that blowing jumbo-jet-sized holes in 2 sides of a tower left the tower structurally intact.
(DIR) Post #ATJikzbPQa8F7EbO8O by PJ_Evans@mastodon.social
2023-03-05T20:54:22Z
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@lauren Usually the central core is a fair amount of building area, and includes the elevators and the stairwells. But that one - I was never in it, so I don't know.
(DIR) Post #ATJkF7bwJgWiaymSzA by lauren@mastodon.laurenweinstein.org
2023-03-05T21:11:01Z
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@tknarr Structurally intact for some minutes.
(DIR) Post #ATKNs9QROsiLjH0IbI by melissadancey@mastodon.au
2023-03-06T04:35:00Z
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@lauren None would imagine something like this attack would happen to these buildings. The buildings were probably built to the 1960s/1970s code. One of my grandmother's cousins used to work in one tower. On the day of the attack, he was running late to work.
(DIR) Post #ATKR6GjDLSkmIMCysy by tknarr@mstdn.social
2023-03-06T05:11:06Z
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@lauren For an hour (south tower) to an hour and a half (north tower) after impact. North tower was hit at 8:46am and started to collapse at 10:28am. South tower was hit at 9:03am and started to collapse at 9:59am.
(DIR) Post #ATKtA7BdYlxIZr7pIW by Dervishpi@mastodon.social
2023-03-06T10:25:37Z
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@lauren Interesting discussion. I remember visiting in '76, but of course had no idea of the peculiarities of its construction.I was so surprised at how it collapsed, and could imagine the added chaos if they had fallen sideways, but it always seemed strange that all the lower floors were destroyed.
(DIR) Post #ATLfF8R18tqnhCmLdQ by InkomTech@infosec.exchange
2023-03-06T19:24:15Z
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@lauren @cstross as a fellow risk analyst, your comment seems like folktale-grade analysis. The WTC/911 reports don’t decry fire doors OR structural design as significant problems. Quite the contrary. And ‘seemed odd to me’? Cite a skyscraper struc engineer. Can’t, because the damn buildings behaved admirably: an immediate collapse would have caused an order of magnitude more deaths. 20,000 gals of jet fuel took an hour to an hour and a half to get thru fireproofing on structural steel enough to cause a collapse. That is insanely well-engineered, given it isn’t even a tested scenario.