What are the secrets for Forbidden City to surviving so many earthquakes in 600 years?

To find the answer, specialist carpenters have built a one to five-scale model to replicate the classic Forbidden City structure on a wobbling table to simulate earthquake forces.

To be as accurate as possible, the model is made using traditional Chinese carpentry tools and techniques.

The seismologist subjected the scale model to a series of simulated quakes, from magnitude 9.0 to 10.1 that have the equivalent energy to well over 2 billion tonnes of TNT.

In the tests, the stone bases were shifting around, but nothing in the scaled building structure was damaged.

So what are the secrets to the ultra-flexibility of the traditional Chinese building structure?

The first key is the huge flower-shaped Chinese-style bracket called dougong sitting on the cross beams under the roof. The intricate dougong brackets extend to the exterior to support the eaves as well as the roof and act as a retarder when the structure shifts.

The second key is the unique Chinese mortise and tenon joints without the use of a single nail. The difference between a pure tent structure and a hardbound structure is like that between human bone joints and medical splints.

The third key is the tall columns that support the beams. The beams are not founded on the earth but free-standing.

All these structural parts bear the roof’s immense weight while being able to readjust their own position when the land moves.

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