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YouTube // Practical Engineering

Making Skyscrapers Sway Less: Tuned Mass Dampers

YouTube // Practical Engineering
YouTube // Practical Engineering

When we build super-tall skyscrapers, those buildings are subject to swaying due to wind and seismic activity. They're designed for it, and some amount of movement is both safe and inevitable...but it can be really unpleasant for people in the upper floors. So what can engineers do to reduce this movement, but preserve the flexibility of the building?

Enter tuned mass dampers (previous coverage). TMDs are used in all kinds of things, from cars to power lines to spacecraft (!). They offer a counterweight that offsets vibration, counteracting the most troubling movement within a given structure.

Okay, so how do TMDs work? In this video from Practical Engineering, we get a great demo, including a small-scale build in the video-maker's garage to show the effects of a simple TMD system. Tune in and learn a bit of awesome engineering:

(Note: Bonus points for the googly eyes on the demo skyscrapers! If only we had those on real skyscrapers....)

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NASA/JPL, YouTube
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Space
Watch NASA Test Its New Supersonic Parachute at 1300 Miles Per Hour
NASA/JPL, YouTube
NASA/JPL, YouTube

NASA’s latest Mars rover is headed for the Red Planet in 2020, and the space agency is working hard to make sure its $2.1 billion project will land safely. When the Mars 2020 rover enters the Martian atmosphere, it’ll be assisted by a brand-new, advanced parachute system that’s a joy to watch in action, as a new video of its first test flight shows.

Spotted by Gizmodo, the video was taken in early October at NASA’s Wallops Flight Facility in Virginia. Narrated by the technical lead from the test flight, the Jet Propulsion Laboratory’s Ian Clark, the two-and-a-half-minute video shows the 30-mile-high launch of a rocket carrying the new, supersonic parachute.

The 100-pound, Kevlar-based parachute unfurls at almost 100 miles an hour, and when it is entirely deployed, it’s moving at almost 1300 miles an hour—1.8 times the speed of sound. To be able to slow the spacecraft down as it enters the Martian atmosphere, the parachute generates almost 35,000 pounds of drag force.

For those of us watching at home, the video is just eye candy. But NASA researchers use it to monitor how the fabric moves, how the parachute unfurls and inflates, and how uniform the motion is, checking to see that everything is in order. The test flight ends with the payload crashing into the ocean, but it won’t be the last time the parachute takes flight in the coming months. More test flights are scheduled to ensure that everything is ready for liftoff in 2020.

[h/t Gizmodo]

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Christopher Furlong/Getty Images
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architecture
German Nonprofit Gives $1.1 Million to Restore World’s First Iron Bridge in England
Christopher Furlong/Getty Images
Christopher Furlong/Getty Images

The UK’s Iron Bridge is more than just a pretty landmark. Built in 1779, it was the world’s first metal bridge, a major milestone in engineering history. Like many aging pieces of infrastructure, though, it’s in dire need of repair—and the funds to shore it up are coming from an unexpected place. According to The Times, a German foundation has pledged to pay for the conservation project as a way to improve relations between England and Germany in the wake of Brexit.

Based in Hamburg, the Hermann Reemtsma Foundation normally funds cultural projects in Germany, but decided to work with the UK’s charitable trust English Heritage to save the Industrial Revolution landmark as a way to reinforce the cultural bond between the two countries. The foundation has pledged more than $1.16 million to the bridge's renovation effort, which will cost an estimated $4.7 million in total. Now, the UK charity only has to raise another $32,800 to fully fund the work.

The Iron Bridge was cast and built by Abraham Darby III, whose grandfather became the first mass-producer of cast iron in the UK in the early 1700s, kickstarting England's Industrial Revolution. It was the world’s first cast iron, single-span arch bridge, weighing more than 400 tons. In 1934, it was declared a historic monument and closed to traffic, and the Ironbridge Gorge was named a UNESCO World Heritage Site in 1986.

“The Iron Bridge is one of the most important—if not the most important—bridges ever built,” English Heritage CEO Kate Mavor told the press.

The techniques used to erect the Iron Bridge were later adopted throughout Europe, including in Germany, leading the Hermann Reemtsma Foundation to call it “a potent reminder of our continent's common cultural roots and values.”

The already-underway repair project includes replacing elements of the bridge, cleaning and repairing others, and painting the entire structure. Since it sits above a fast-flowing river where erecting scaffolding is difficult, the project is especially complex. It’s scheduled to be completed in 2018.

[h/t The Times]

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