Be aware of speed

From some of the already published examples, it can be seen that the mechanism of seismic control effectively reduces the shaking caused by earthquakes. Simply put, the mechanism of seismic control is a mechanism that converts the seismic energy applied to a building by seismic motion into heat energy and other energy, which is then absorbed to suppress shaking. How does it convert the seismic energy? It focuses on the speed of the vibration caused by the earthquake and uses dampers that work according to the speed. There are dampers that move viscous bodies such as oil, and those that use friction between steel materials. A special type of damper transfers the shaking of the building to a weight placed on the roof, and absorbs the seismic energy through the movement of the weight. Seismic isolation structures, which have expanded rapidly since the Southern Hyogo Prefecture earthquake, also have a large number of dampers that absorb vibration energy in addition to seismic isolation devices that reduce shaking, and effectively reduce shaking. From that point of view, seismic isolation structures can also be considered as seismic control in a broad sense. This seismic control prevents damage to ceilings and toppling furniture, and the after-shocks that occur in high-rise buildings subside in a relatively short time.

Dealing with earthquake motion by focusing on speed is the highest achievement of earthquake-resistant design technology at present. A wide variety of specific devices and their effective placement methods have been developed. Taking this a step further, a system is also being developed to efficiently generate electrical energy from vibration energy. Of course, in this case, the vibration energy being targeted is not the rare earthquake motion, but vibrations that are constantly present, such as wind and waves.

Being aware of speed and controlling it well is also an important aspect of tsunami countermeasures for buildings, which became a new issue as a result of this earthquake. The force that a tsunami exerts on a structure is proportional to the flood height, but increases exponentially as the force and speed of the water increases. Therefore, in order to fight it as a force, you must properly grasp the speed. If there is a mechanism in place to weaken the force of the tsunami before it hits the structure, the force of the tsunami will be reduced, so creating such a mechanism well is also effective. Of course, if you decide that you must flee, your fleeing speed must be faster than the speed of the pursuer.

Controlling the speed and being conscious of the speed is also an important perspective for the business of reconstruction. Reconstruction plans that consider what the town should be like tend to be static and off-time. And there is probably no reconstruction plan that is convenient for everyone. A plan that has a weak time axis and cannot be agreed upon by everyone will not proceed easily. If we are conscious of the speed of reconstruction, we will place emphasis on the restoration of human activities. Here, human activity is, first and foremost, production. A wide range of productive activities, from agriculture, fishing, and industry to commerce, distribution, tourism, and education, must be quickly restored. To do this, the time axis of the seasons and market conditions will be important. I am worried that if the timing is off, we may not even be able to recover. These things may be at the level of recovery, but since there must have been a desire to do this in the future even before the earthquake, starting the recovery will lead to reconstruction. And if reconstruction starts and the speed becomes more conscious, reconstruction will probably progress at an accelerated pace.