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How the evacuations from the twin towers helped make today’s skyscrapers safer

3 points by imartin2k 5y ago

anshumankmr 5y ago
""" There were too few stairwells The stairs in the twin towers were, to a great extent, a product of their times. In 1968, as construction on the towers was beginning, New York City issued a brand-new building code, allowing for substantial reductions in egress capacity from the previous code dating to 1938. It appears that the buildings’ owner, the New York Port Authority (now known as the Port Authority of New York and New Jersey), took advantage of this fact, providing only three stairwells in the center core of each tower, instead of the six that would have been required under the older code. Labeled simply A, B and C, the stairwells encompassed the buildings’ entire height; two were 44 inches in width, one was 56 inches wide. The fact that the buildings’ designers wanted wide-open floors without columns and other obstructions meant that the three staircases, bathrooms, elevators, and other service elements were all placed in the same central area of the massive one-acre floors. In the case of the north tower, the stairs were approximately 70 feet apart; in the south tower, they were about 200 feet apart. But what wasn’t there on 9/11 was a fourth stairwell in each tower, one that would have led from the Windows on the World restaurant in the north tower and another from the observation deck atop the south tower. These two high-occupancy spaces, each exceeding 1,000 people, needed additional egress capacity. But those code-mandated fourth stairwells didn’t exist because the New York Port Authority chose not to include them; the Port Authority was, and continues to be, exempt from actually complying with New York City’s building code. """ . . . """ Ironically, the need for wider stairs—going from 44 inches to 56—only found its way into one of these two national building codes. Unfortunately, it isn’t the code under which most new high-rises across the United States are being built today. And that includes New York City. """ This is an interesting article about the flaws in the design that possibly led to more deaths.Be advised that it will be quite hard to read, especially for those who saw it happen. https://www.history.com/news/world-trade-center-stairwell-design-9-11 https://www.history.com/news/world-trade-center-stairwell-de...
- phendrenad2 5y ago
  Wait, let me sit down. And see if I'm following this correctly. The city of New York, a government entity, built the World Trade Towers. And when they started construction, they ran into planning issues and said "fuck it" and changed their own regulations. Then they ran into more issues and said "fuck it" again and disregarded the regulations entirely? I can't imagine all of the private companies, who have to follow the laws, and can't just change them with the stroke of a pen, or ignore them, are happy about this.

3 points by imartin2k 5y ago

""" There were too few stairwells The stairs in the twin towers were, to a great extent, a product of their times. In 1968, as construction on the towers was beginning, New York City issued a brand-new building code, allowing for substantial reductions in egress capacity from the previous code dating to 1938. It appears that the buildings’ owner, the New York Port Authority (now known as the Port Authority of New York and New Jersey), took advantage of this fact, providing only three stairwells in the center core of each tower, instead of the six that would have been required under the older code. Labeled simply A, B and C, the stairwells encompassed the buildings’ entire height; two were 44 inches in width, one was 56 inches wide. The fact that the buildings’ designers wanted wide-open floors without columns and other obstructions meant that the three staircases, bathrooms, elevators, and other service elements were all placed in the same central area of the massive one-acre floors. In the case of the north tower, the stairs were approximately 70 feet apart; in the south tower, they were about 200 feet apart. But what wasn’t there on 9/11 was a fourth stairwell in each tower, one that would have led from the Windows on the World restaurant in the north tower and another from the observation deck atop the south tower. These two high-occupancy spaces, each exceeding 1,000 people, needed additional egress capacity. But those code-mandated fourth stairwells didn’t exist because the New York Port Authority chose not to include them; the Port Authority was, and continues to be, exempt from actually complying with New York City’s building code. """ . . . """ Ironically, the need for wider stairs—going from 44 inches to 56—only found its way into one of these two national building codes. Unfortunately, it isn’t the code under which most new high-rises across the United States are being built today. And that includes New York City. """ This is an interesting article about the flaws in the design that possibly led to more deaths.Be advised that it will be quite hard to read, especially for those who saw it happen. https://www.history.com/news/world-trade-center-stairwell-design-9-11 https://www.history.com/news/world-trade-center-stairwell-de...

phendrenad2 5y ago
Wait, let me sit down. And see if I'm following this correctly. The city of New York, a government entity, built the World Trade Towers. And when they started construction, they ran into planning issues and said "fuck it" and changed their own regulations. Then they ran into more issues and said "fuck it" again and disregarded the regulations entirely? I can't imagine all of the private companies, who have to follow the laws, and can't just change them with the stroke of a pen, or ignore them, are happy about this.