Many survivor accounts of those who escaped from the building tell tales of destruction on various floors.
"On the 20th floor of Tower One, Leder and a friend, Bill Forney, 28, of Manhattan, saw a woman who seemed exhausted. She was telling others to pass her by on the stairs. It was Juliette Bergman.
Leder and Forney stopped to help. Earlier, they had faced their own ordeal. Heading downstairs, the two had hit a dead end at 72. The stairs just didn't go any farther, they said. Leder and Forney found a door to another stairwell, but it was locked.
The situation was bad. "There were fires all over" the 72nd floor, Leder said. "No walls, wires everywhere."
http://www.newsday.com/news/local/newyork/ny-nytic242381668sep24.story?coll=ny-top-headlines-------------------
Perhaps certain sections (lesser members?) of the core were blown at 10 story or so intervals simultaneous with the plane impacts.
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"Many stayed. Baumbach did not.
At 10-story intervals, he had to walk through burning corridors. Bizarrely, no sprinklers or alarms had been activated."
http://www.newsday.com/news/printedition/newyork/ny-nyesc132363611sep13.story"I am working for Lehman Brother's equities e-commerce website, we are located on the 40th Floor in One World Trade Center,
Lots of people joined us from other floors. Then we see heavy smokes coming in from the 33-34th floors, the line paused, we hesitated for a while, wandering if we should keep going down in the smoke, then we slowly moved on, I covered my mouth and nose with a piece of facial tissue, we keep talking to each other, I guess there must be a fire going on at certain floors, we kept walking down the stairs, the smoke became more and more dense"
http://66.218.71.225/search/cache?p=trade+center+elevator+fire&ei=UTF-8&url=3Hrt-dcZjdkC:www.miraclebridge.com/wtcescape.html"
"As Shearin exited the elevator on his visit to a tenant on the 38th floor of 1 WTC, he was hurled in the air from a sudden, loud explosion. Corridors quickly filled with panicked occupants; his immediate response was “continue down the stairs and out of the building” as he walked up three floors to the mechanical equipment room to inspect what he thought might have been the source of the problem................
"The 41st-floor mechanical room had sustained considerable damage – equipment formerly located in the ceiling was down on the floor and water was gushing from crushed pipes. After ascertaining the room was vacant, Shearin proceeded to Level B-2, the location of the engineering office, and then to the lobby where destruction – to people and to the building – was devastatingly evident. Shearin offered assistance to the injured;"
http://www.buildings.com/Articles/detail.asp?ArticleID=925"When I reached the 44th floor sky lobby, I noticed many people
milling around and wondering. The wall-mounted flat screen television above the entrance to the cafeteria was displaying a business news station. I could see the electronic ticker tape moving from right to left on the bottom of the TV monitor. A rumor in the lobby was circulating that a single engine plane or a helicopter had hit the North tower. Events were downplayed frequently that day.An announcement came across the public address system. "An airplane had hit OneWorld Trade but the integrity of Two World Trade was okay". This message was repeated once more. I heard two young men say they were going return to work as they headed towards their elevator. As I took a few steps towards someone I recognized, some great force struck my building. It felt like the floor was being violently pushed under my feet. While falling to the floor, the steady repeating rhythm of time suddenly stopped. I instantly developed tunnel vision
and my depth perception did not extend beyond twenty feet. My eyes focused on a nearby out-of-service elevator. The impact had created a shock wave through the entire building that forced dust at a high velocity from all four sides of the elevator doors to the inside of the lobby. I was now prone on the floor. Pandemonium erupted and filled the sky lobby."
"http://www.laurasmidiheaven.com/world-trade-center/"
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Most accounts describe explosions origniating from the elevators, hence the jet fuel fire ball theory.But the same pattern of destruction was seen in both buildings even though the plane hits were considerably different. And many elevators were "closed for construction" , including the large room size express elevator in both buildings, which went from the lobby to the top floors (windows of the world in tower 1 and the observation deck in tower 2). Both of these elevators were closed for a month prior to 9/11. Remember all of the elevator shafts were within the core.