Rotating inertial mass dampers were developed as a vibration control device and have been applied to actual buildings in recent years. An inertial mass damper is able to generate an inertial force of thousands of times of their mass weight by the inertial mass effect determined by the diameter of the flywheel and the lead of the ball screw. The damper then reduces an earthquake response owing to the inertial force acted on the structure.
In this paper, we conducted full-scale vibration tests on three types of inertial mass dampers with inertial masses of 2,500 ton, 4,000 ton, and 6, 500 ton, and clarified the mechanical characteristics of the dampers in the temperature range from 0 °C to 40 °C. We proposed a dynamic model of the damper that is able to express the vibration test results and verified its validity. The proposed dynamic model considers the inertial mass, the viscous damping force and the friction force of the damper as mechanical characteristics. We examined the variation of the mechanical characteristics and the durability of the damper by repeated vibration tests. The inertial mass damper has an overload prevention mechanism to avoid excessive reaction forces. In the test, we have targeted the range which the overload prevention mechanism operates (relief) and large displacement occurs in the damper. The obtained results are as follows;
(1) The generated inertial mass is found to be almost constant irrespective of the vibration frequency, the amplitude and the temperature. The frictional force depends on the temperature, and increases as the temperature decreases. The viscous damping force depends on the temperature and the vibration frequency. We proposed the correction formula that is able to estimate the viscous damping coefficient at given temperature and excitation frequency.
(2) The slope of the force-displacement relationship after the relief mechanism operates corresponds with the inertial mass of the ball nut. The maximum load increases in both the compression side and the tensile side due to the difference between the static friction and the dynamic friction in the relief mechanism. The burden on the tensile side is larger than that on the compression side.
(3) Repeated vibration tests were carried out until the cumulative rolling distance reaches 100 m, and no change in the mechanical characteristics was observed.
(4) We developed a structural analysis model of the damper that comprises the inertial mass element, the viscous damping element, the friction element connected in parallel. The relief mechanism was modeled as a friction element that takes into consideration the difference between the dynamic friction and the static friction and the asymmetry of the positive and negative loads. The proposed model is able to accurately express the hysteresis characteristics obtained by the experiments.
