In early 1962, when port authorities in New York and New Jersey officially authorized a plan to build the World Trade Center in Lower Manhattan, it came just months after President John F. Kennedy announced the plan to build the World Trade Center in Lower Manhattan. US objective to send astronauts to the moon. The vision for the seven-building complex – which would cost around $ 470 million (over $ 4 billion in today’s dollars) and include the two tallest buildings in the world – embodied the same brand of optimism and d American ambition.
The 110-story twin towers at the heart of the World Trade Center were designed to surpass New York’s iconic Empire State Building, then the tallest building in the world. The construction of the new towers would mobilize unprecedented levels of design innovation, engineering prowess–and breathtaking risk.
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1. A little-known Japanese-American architect was chosen to design the World Trade Center.
Born into a poor family of Japanese immigrants in Seattle, Washington, Minoru Yamasaki received his college education working in fish canneries in Alaska. He started his career in New York, working for the company that built the Empire State Building, and moved on to run his own business in Detroit. By 1962, when Yamasaki asked to design the World Trade Center, he had completed work on a single high-rise building: Detroit’s Michigan Consolidated Gas Tower, which was only 30 stories tall.
The Port Authority chose Yamasaki based on its proposal to design a sprawling mall that still had the intimate, human-centered qualities of its other designs. Responsible for constructing the tallest building in the world, Yamasaki opted for a design of two towers and five other buildings that together would include some 15 million square feet of office space.
2. The owner of the Empire State Building helped build opposition to the World Trade Center project.
Perhaps motivated by self-interest as well as worry, a group of major New York City real estate developers (unsuccessfully) challenged the Port Authority to scale back its proposal for the World Trade Center from 1964. Led by Lawrence Wien, an owner of the Empire State Building, the Committee for a Reasonable World Trade Center joined a growing number of critics claiming that the Twin Towers would be unstable at such a massive height and dangerous if collided. plane or fire. In 1968, Wien even put out an almost full-page newspaper ad with an artist’s rendition of a commercial plane about to fly straight into the upper floors of the North Tower.
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3. To build a deep foundation that would not be flooded by the nearby Hudson River, engineers used an innovative “slurry trench” method.
The construction of what was then the tallest building in the world posed one of the most difficult foundation projects ever encountered on Manhattan Island. The site chosen for the project was built on a landfill that had gradually extended from the west side of Lower Manhattan to the Hudson for some 700 feet over the centuries. The foundation for the Twin Towers required digging 70 feet to bedrock and excavating over a million cubic meters of earth.
To avoid flooding the site, workers dug a trench 3,500 feet long and 3 feet wide around the perimeter of the site (made up of over 150 sections of 22 feet long) and filled it with ‘a mud composed of water and bentonite, an absorbent clay. Because the mud was denser than the dirt around it, it kept the dirt from filling the trench. Steel cages of about seven stories and weighing 25 tons each were then lowered inside the trench panels and the concrete poured around them, forcing the lighter’s suspension up and out. The completed foundation was commonly known as a “tub,” although it was a tub that kept water out and not in.
4. The design of the Twin Towers provided stability from the outside to the inside, without a forest of interior support columns.
Traditional skyscrapers owed their stability to a system of large vertical columns crossing each floor at 15 to 30 foot intervals, with the exterior walls alone providing little support. But in order to open up the vast expanses of office space required in the planned Twin Towers, engineers placed most of the strength of the buildings outside, essentially creating rigid tubes of heavy steel. The innovative design allowed for minimal columns inside, most of them clustered in the center of the building to maximize the amount of open space on each floor.
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5. Although made from heavy-duty steel, the towers have been designed to sway in strong winds.
The builders of the World Trade Center conducted extensive research into the effect of wind on towers, commissioning one of the first wind tunnel studies for a skyscraper and performing perception tests disguised as eye exams on unsuspecting subjects to determine how far the building might sway. strong winds without anyone noticing. To ultimately mitigate the effects of the wind, engineers distributed over 10,000 “viscoelastic shocks” – made from a viscous but still flexible combination of metal, epoxy and polyacrylic glue – into each tower. With this advanced damping system in place, the towers were designed to be able to sway up to three feet back and forth in windy weather.
6. To hoist hundreds of thousands of pounds of steel to dizzying heights, builders imported “kangaroo” cranes.
In total, workers used some 200,000 tons of steel to build the Twin Towers of the World Trade Center. But getting this steel to the top of the building during construction posed a thorny challenge, as the planned height of the towers exceeded even the tallest cranes in the world at the time. So engineers turned to an Australian-designed autonomous crane dubbed the “kangaroo crane” that used a heavy-duty hydraulic system to “jump” up to three floors at a time as the towers rose.
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7. The innovative design of the elevator was inspired by the New York subway.
With 110 floors in each tower, the engineers took on the challenge of designing an elevator system that would not consume a gigantic share of the available space inside the building. Their solution mimicked the city’s local and express metro system: they divided the building into three zones, each served by an express elevator. People would get off at one of the building’s “aerial lobbies”, then take the local elevators to the floor of their choice. This system allowed engineers to use much less space for elevator shafts, dramatically increasing the amount of rentable space in each tower.
8. With its exemption from local building codes, the Port Authority has halved the number of stairwells in towers.
In addition to the elevators, the decision to place the building’s stairs in the center of each tower was also designed to maximize open office space. At the time of the construction of the World Trade Center, city building codes required six staircases for tower-height buildings. But as an interstate agency, the Port Authority was exempt from such codes. He chose to follow a new building code that only required three stairs, a move that would have devastating consequences on September 11.