Highly efficient core rod vibration control system

Where should vibration control devices such as dampers and laminated rubber that reduce the energy of shaking be placed most efficiently? After considering this issue, we developed a new vibration control system technology called a core rod frame. Vibration control devices are effective when placed in locations where the shaking and displacement of building components due to earthquakes is greatest.

So we tried inserting a "core rod," a rigid structural component that is independent of the surrounding area, into the center of the lower part of the building. Because the core rod is rigid, it does not deform much itself, and the difference in displacement with the surrounding areas is concentrated at the bottom. The relative displacement that occurs on each floor is transmitted to the bottom. Placing the vibration control device at the point where the displacement with the surrounding area is greatest increases efficiency.

Let's take a look at one structural model. We'll assume a 30-story building made of steel and 3 basement floors made of steel-framed reinforced concrete. A highly rigid concrete structure, which acts as a core rod, is inserted in the lower floors, from the 3rd basement floor to the 5th floor. This core rod is separated from the surrounding structure to allow it to move with clearance. At the same time, laminated rubber is attached to the bottom as a support material, and it is also separated from the foundation. Therefore, when the building shakes, there will be a difference in the amplitude of the vibration between this core rod and the surrounding steel structure. This is where the viscous oil damper is installed. The damper acts as a vibration control device, attenuating the vibration caused by the difference in the amplitude of the vibration. When comparing this model with a general model in which vibration control devices are distributed on the reference floors, the number of viscous dampers required is 1/5. In other words, the device works 5 times more effectively.

Although there is a gap between the core rod and the surrounding area, by using the core rod area as the core of the building, planning is not unreasonable. For example, if it is used as a mid-to-high-rise elevator shaft, there is no need to connect floors at the lower levels. It is also suitable for the use of recent skyscrapers, where the 5th floor and below are used for commercial and facility purposes.

However, a major challenge was how to connect the rigid core rod of the lower floors to the flexible steel structure of the mid- and upper-floor sections. Stress would be concentrated at the connection. To address this issue, rigid steel dampers were installed in the upper middle section of the core rod. The idea is that a rigid core of steel structure extends continuously above the stiffest core rod. No clearance is required in the damper section on this floor, allowing for continuous planning. It plays a role in appropriately transmitting the force of an earthquake to the core rod in the mid- and upper-floor sections.