Why do some people say that the earthquake resistance of the Forbidden City is 10?

What is the basis of the "strong earthquake does not fall" shown in the model of the Forbidden City? In my opinion, China is the first country in the world to apply the concept of isolation to buildings. In the design and construction of the Forbidden City, the seismic demand was fully considered, and a number of isolation technologies were adopted.

The so-called building isolation is to place a movable device at the foundation of the building; When an earthquake occurs, some seismic energy is dissipated and absorbed by the motion of the device, so that the frequency of seismic waves is staggered, thus reducing the damage to buildings caused by earthquakes.

How is the isolation of the ancient buildings in the Forbidden City achieved? For example, Qian Zhou explained that the pillars of a building are not inserted into the ground, but placed on the pillars. Under the earthquake, the column root moves back and forth on the top stone of the column, which produces the effect of friction and sliding isolation.

The beams and columns of the ancient buildings in the Forbidden City are connected in the form of tenons, and the ends of the beams are made into tenons and inserted into the mortises reserved at the top of the columns. Under the earthquake, the tenon and mortise repeatedly opened and closed and rotated, and a small number of tenons were pulled out. To tenon is to pull the tenon out of the mortise, but it is not tenon, and the tenon is always in the mortise position. This relative rotation is also the embodiment of friction damping and isolation mechanism.

Above the top of the column is a bucket arch. Bucket arch is composed of small-sized frames such as sitting, arch, tilting and lifting from bottom to top. Under the earthquake, these small components are squeezed and staggered, which can dissipate a lot of earthquake energy, prolong the shaking period of buildings and produce isolation effect. After the earthquake, these widgets can basically be restored to their original positions and remain intact. In addition, the thick roof is like a fat man, which swings back and forth under the action of external force, but it remains stable all the time, which has a good isolation effect.