The Tokyo Sky Tree’s secret weapon against earthquakes

Posted on by Jeffrey

Sky Tree

The above is not a side-by-side comparison of the size of the Tokyo Sky Tree and some ancient gigantic pagoda. However, it is a side-by-side comparison of the technology used in creating a tall, stable structure. The frequency of earthquakes and typhoons in Japan make building codes much stricter than anywhere else in the world and provided the architects and engineers behind the Tokyo Sky Tree with plenty of challenges. Most importantly, how will the largest freestanding tower in the world be able to withstand a 8.0 magnitude earthquake?

At 634 meters, the Sky Tree is now the tallest freestanding tower in the world, existing in one of the most geologically and climatically turbulent areas in the world. To address these issues, when engineers began designing the tower, they took a page from their ancient ancestors and created a shinbashira within the Sky Tree. A giant tube of re-enforced concrete, the shinbashira is separate from the Sky Tree’s outer shell and acts as a counterweight. In computer simulations, due largely to the shinbashira, the Sky Tree can withstand an earthquake of at least 8.0 magnitude. In fact, engineers aren’t sure what the Sky Tree’s limits are!

Estimated to originate around the 7th century, shinbashira are a distinctly Japanese characteristic of their famous pagodas. Originally whole tree trunks stripped of bark, the shinbashira is suspended from the top of the pagoda, carrying load, and apparently having no structural role. Sometimes it rests gently against the ground, sometimes it dangles above ground or above the ceiling over the first floor. Seemingly, ancient Japanese engineers, through trial and error, discovered that the best way to counteract the collapse of a structure due to excessive shaking from winds or earthquake was to create an interior counter-weight. A true achievement in engineering that has stood the test of time.

Sky Tree Interior

Thanks, Economist, CNNGo, MSNBC, and JAANUS!

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