Kenichiro Ohmata

A Study on an Elastoplastic Damper Utilizing Continuous Plastic Bending of Metal Rods. In the Cases of an Improved Damper and a Compound Damper.

In the previous paper, an elastoplastic damper utilizing continuous plastic bending of thin metal rods was developed. In this paper, an improved damper that is improved a winding mechanism of the metal rods of the elastoplastic damper for a larger resisting force and a compound damper that is added a friction mechanism as a fale-safe mechanism to the elastoplastic damper are proposed. The trial dampers were made and the resisting force characteristics and fatigue strength of the dampers were measured. The seismic responses of an L-shaped pipe supported by the dampers were also measured using an electrohydraulic shaking table.

A Study on a Elastoplastic Damper Utilizing Continuous Plastic Bending of Thin Metal Rods.

In this paper, a new type of elastoplastic damper utilizing continuous plastic bending of thin metal rods is proposed in order to obtain an elastoplastic damper which yields damping even for a small displacement. The seismic responses of a piping system supported by the elastoplastic damper were calculated using a continuous system simulation language and the effects of the damper on the deflection of the piping system are discussed. The trial damper was made using a thin copper rod, and the resisting force characteristics and fatigue strength of the damper were measured. The seismic responses of an L-shaped pipe supported by the trial elastoplastic damper were measured using an electrohydraulic shaking table. The experimental results were compared with the calculated results.

Elastoplastic-Friction Damper Using V-Shaped Plates.

In this paper, an elastoplastic-friction damper is proposed as a hysteresis damper which provides damping even in the case of small displacement. The damper is composed of an elastoplastic damper using V-shaped plates and a friction damper consisting of V-shaped springs, brake shoes and a brake plate. The relationship between the force and displacement of the damper was analyzed, and the resisting force characteristics and fatigue strength of the damper were measured. An experimental model of a machine-isolation device system using the damper was also made, and the seismic responses of the system were measured using an electrohydraulic-type shaking table. The experimental results were compared with the calculated results.

Semiactive Damper Using a Piezoelectric Actuator and a Ball Screw for a Seismic Isolation Device for Machines.

In this paper, a new type of semiactive seismic isolation device for machines is proposed. This isolation device is composed of rubber bearings and semiactive dampers consisting of a ball screw, a brake disk, a brake shoe, a flexure hinge and a piezoelectric actuator. The seismic responses of a machine supported with the isolation device, which is installed on the 5th floor in a 7-story building, are calculated using a continuous system simulation language (FACOM SLCS4), and the effective control condition of the semiactive damper is discussed. An experimental semiactive damper and a model of a machine-isolation device system are made, and the resisting force characteristics of the damper and the seismic response of the machine are measured using an electrohydraulic-type shaking table. The experimental results are compared with the calculated ones, and the effect of vibration isolation of the isolation device is confirmed.

Development of an Earthquakeproof Device Using Magnetostrictive Actuators for Piping Systems.

The mechanical snubber is an earthquakeproof device for a piping system under high temperature. It follows a slow displacement of the piping due to thermal expansion, but restrains the piping by a strong resistance force during an earthquake. This strong force can cause elastic failure of grooves on a brake disk, where steel balls are placed. In this report, a new semiactive snubber using giant magnetostrictive actuators and a ball screw is proposed in order to obtain an earthquakeproof device which has less resistance force in comparison with the mechanical snubber. Earthquake responses of a simple beam supported by the semiactive snubber are simulated using a continuous system simulation language, and the restraint effect and the effective controlling condition of the snubber are discussed. The semiactive snubber is built using Terfenol-D (Tb0.3 Dy0.7 Fe1.92-1.95) rods, and its resistance force characteristic is investigated by means of a vibration table.