March 22, 2012

The Konpon Dai-tô

The Japanese pagoda ( means "pagoda") evolved from stupa built to contain relics of the Buddha (discussed here). The structure symbolizes the Five Elements--earth, water, fire, air and space. Pagoda architecture also provides early examples of earthquake proofing using pendulum damping.

The biggest architectural difference is that Japanese pagodas are always made out of wood, also because of earthquakes.

The pagoda is framed around a central pole (真柱), usually the trunk of a large cedar tree. Except that in a finished pagoda, the central pole is not load-bearing. The weight of the structure is carried by the outside supporting pillars that define the square shape of the pagoda's floors.

The central pole instead serves to dampen the sideways motion of the upper floors (cantilevered and inertially stable), and channels that energy into the ground. Tokyo's 2,080 foot Sky Tree also employees a central stationary pendulum, along with a pair of tuned mass dampers.

I don't think it mere coincidence that the digital television antennas perched atop the Sky Tree closely resemble the surprisingly futuristic finials that have graced the roofs of pagodas for centuries.

Courtesy Wikimedia Commons.

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