Kawakin Core-Tech Co., Ltd. (Headquarters: Kawaguchi City, Saitama, President: Shinichi Suzuki), in collaboration with Toda Construction Corporation (Headquarters: Chuo-ku, Tokyo, President: Seisuke Otani) and Koyo Seiki Co., Ltd. (Headquarters: Chikusei City, Ibaraki, President: Shinichi Suzuki), has developed a "self-restoring trigger mechanism oil damper" to ensure building safety during major earthquakes. Generally, oil dampers have the function of suppressing building sway from small to large earthquakes, but this oil damper is not functioning during small earthquakes. Instead, it has a mechanism that only activates the damper when a large earthquake causes large deformation in the seismic isolation layer. This  "self-restoring trigger mechanism oil damper" technology was certified by the Japan Building Center on September 9th, 2022, and is currently being implemented in the new Toda Construction Corporation headquarters building "TODA BUILDING," aiming for the highest level of earthquake resistance in Japan.

1. Development Background

In recent years, it has been reported that extremely large tremors occur in super-high rise buildings and seismically isolated buildings that resonate with the earthquake tremors (Note 1) in long-period earthquakes, which have been attracting attention. In addition, in the event of a Tokyo metropolitan earthquake or a Nankai Trough earthquake, which are predicted to occur with a high probability in the future, seismically isolated buildings may collide with the surrounding retaining walls (Figure 1), causing significant damage.
A conventional approach to suppress large tremors in base-isolated buildings is to increase the number of dampers (increasing damping (Note 2)). However, while this method helps control large tremors, it also increases the building's acceleration during smaller and medium-sized earthquakes, partially reducing the effectiveness of the base isolation.
The "self-restoring trigger mechanism" is a unique passive damping switching mechanism that does not require electricity, developed to solve this problem (Photo 1).

(Note 1) A phenomenon in which, when subjected to vibration with the same period as the natural period of the building, the structure vibrates much more strongly than the vibration it receives from the earthquake. Skyscrapers and isolated buildings are prone to resonance during long-period vibration.

(Note 2) The phenomenon in which vibrations decrease over time.

2. Self-restoring trigger mechanism

The self-restoring trigger mechanism is designed to balance the suppression of acceleration during small and medium-sized earthquakes with enhanced safety during major earthquakes by intentionally creating an inactive zone (dead band) where the damper does not function. As shown in Figure 2, the damper is connected to the self-restoring trigger mechanism, making it inactive until a predetermined deformation occurs. This prevents an increase in acceleration during small and medium-sized earthquakes (Figure 3).
On the other hand, the damper functions normally during major earthquakes that exceed the predetermined deformation, preventing the building from swaying excessively horizontally and colliding with retaining walls. Additionally, a restoring spring is implemented in the mechanism, automatically returning it to its original position after deformation and enabling it to function again.
A significant advantage of this mechanism is that it can be implemented simply by connecting it to an oil damper. It has also been certified by the Japan Building Center in September 2022.

３．Future Development

The developed "self-restoring trigger mechanism" has been implemented in the new TODA BUILDING, the new headquarters of Toda Corporation, which is currently under construction. In the future, we will work to popularize this damper and further develop the technology in order to improve the safety of buildings in preparation for major earthquakes, realize high-performance seismic isolation buildings, and make them safer and more secure.

Contact: Kawakin Core-Tech Co., Ltd.

TEL: 048-259-1113 (Representative)

MAIL: info@kawakinkk.co.jp