TedEd: How one design flaw almost toppled a skyscraper

A TedEd by Alex Gendler

In 1978, Diane Hartley was writing her architectural thesis when she discovered something shocking. The Citicorp Center had a fatal flaw in its building plans that could cause it to tumble into a densely populated area. The flaw stemmed from the building's unique structure. The building site was partially occupied by a church, so it was supported by 4 columns. Because the church was at the corner of the block, those columns were also in the middle of each side of the building, rather than the corners. This worried many people, but the architect William LeMessurier used both a 400-ton mass damper and a V-shaped chevron exoskeleton to ensure the building met safety standards. However, the builders assumed that the building would be getting the most wind from the sides. What Hartley found was that because of the positioning of the base, the most stress would actually be on the corners of the building. LeMessurier had built the skyscraper with this in mind, but when he looked at the building plans again, he found that there had been a fatal change he hadn't been informed of. The joints of the exoskeleton were bolted rather than welded, decreasing structural integrity so much that a strong storm could bring it down. A secret plan was launched with the city to weld the joints at night. Construction was completed without the press knowing because it was completed in the midst of a strike. Only years later did magazines and Diane Hartley find out just how close the building had been to falling.

National Geographic: Are we there yet? What happens if the U.S. can't reach herd immunity

By Amy McKeever

    Even though herd immunity isn't necessarily the end of COVID-19 like many people assume, it is an important step toward making sure outbreaks are preventable and fewer in number. Herd immunity occurs once enough people are immune to a disease, either by vaccination or infection, that the virus can no longer find any hosts. This means that the transmission rate would be less than 1. Based on the transmission rate of around 3 to 4 during the early days of COVID, scientists estimated that around 60-70% vaccination would be required for herd immunity, though that number has since risen to 85% due to more dangerous variants. But many health officials in the U.S. are becoming more concerned that we may not reach that number due to a combination of slowing vaccination rates and increased hesitancy and false information.

    The Biden Administration and various state governments are working to try to get more people vaccinated, using tactics like offering free beer or lottery entries for full vaccination. But what happens if the U.S. can't reach herd immunity?

    The most important thing here is that a majority of the almost 50% of people vaccinated are 65 or older or otherwise compromised in the case that they contract the virus. Should they get it now, they are better protected, meaning that death rates will go down a lot, which is key in ending a pandemic. Even if pockets do continue to have outbreaks, they will be controlled, and likely won't cause major shutdowns. In fact, Israel was able to reopen at 54% vaccination with no major side effects.