This study deals with the vibration transmissibility of a vibration isolation device, which is composed of frictional damping and nonlinear softening springs, when its base is harmonically excited. The SCAP method, a type of averaging method, is employed to obtain steady-state responses. The vibration characteristics due to excitation of the base are investigated through the analysis of displacement transmissibility in the steady-state response. In this process, displacement transmissibility for design parameters is analyzed, and the stability of the response is also investigated. The vibration isolation effect due to frictional damping is found to be more effective in the case of the softening spring than in the case of the hardening spring. Additionally, the pattern of the jump phenomenon observed during frequency sweeping, both upward and downward, has been identified.

In this paper, the effect of a dynamic vibration absorber to suppress the response of a base excitation vibration system composed of a cubic nonlinear spring and a friction damper is investigated. And the dynamic absorber consists of a linear spring and a viscose damper. The mathematical models of these systems are governed by second order nonlinear ordinary differential equations. The response characteristics of the system are analyzed using the slowly changing phase and amplitude(SCPA) method, which is one of the averaging methods. As a function of the friction force ratio, It was obtained the locking frequency at which the relative motion starts was obtained, and the regions where the locking occurred. The displacement transmissibility was investigated according to the change of the design parameter, and the optimal design parameters could be found to minimize the displacement transmissibility.

Friction damping is often used as a vibration isolation medium to protect large objects from vibration. In this paper, it is modeled and analyzed a basis-excited nonlinear vibration system with friction damping using the SCPA method, which is one of the averaging methods. The displacement transmissibility and the stability of the steady state response were analyzed seperately for the linear and the non-linear spring systems. The critical frequency at which the relative motion starts was obtained as a function of the friction ratio, and the characteristics of the displacement transmissibility according to the change of the design parameters were investigated. In the case of the nonlinear spring system, the displacement transmissibilities were divided into three types and the motion characteristics were considered. In particular, there was a peculiarity that the displacement transmissibilty curve was separated at specific parameter values.

본 연구의 목적은 마찰력의 크기에 따른 동조질량감쇠기(Tuned mass damper, 이하 TMD)의 성능변화를 조사하고, 이에 기초 하여 TMD의 최적 설계 파라미터를 결정하는 것이다. 일반적인 TMD 설계는 레일의 마찰력을 최소화하는 것을 전제로, 진동수비와 감 쇠비의 최적값이 제시되어 있다. 본 연구에서는 선형점성, 마찰력, 그리고 점성과 마찰을 동시에 가지는 TMD에 대하여 조화하중과 랜덤하중을 사용한 수치해석을 통해 최적진동수비와 최적감쇠비의 변화를 조사하였다. 마찰력의 경우에도 점성감쇠와 같이 특정 크기까지는 제어효율이 증가하나, 특정 값 이상에서는 TMD 성능이 급격히 저하되는 특성을 가진다. 점성감쇠와 마찰력이 동시에 존재하는 경우, 마찰력이 증가함에 따라 최적감쇠비가 감소하였으며, 마찰력의 크기를 반드시 고려하여 최적감쇠비를 결정해야한다. 풍하중을 받는 76층 벤치마크 구조물에 설치된 TMD에 대한 설계를 통해 제안된 최적 파라미터가 제어성능을 향상시키는 데 있어 유효함을 확인하였다.

In this study a hybrid energy dissipation device is developed by combining a steel slit damper and linear-slot friction dampers to be used for seismic retrofit of structures. The hybrid damper has an advantage in that friction dampers are activated for small earthquakes or strong wind while slit damper remains elastic, and both friction and slit dampers work simultaneously for strong earthquakes. Cyclic loading tests of the linear-slot friction, slit, and the combined hybrid dampers are carried out to evaluate their seismic energy dissipation capability.

We have experienced cracking around column bottom and safety check places on a bridge due to lamp post shaken by traffic and wind. So we need to take a measure to decrease stress on lamp post by suppressing vibration. In this study, We have tested how much we can reduce the stress by using an anti vibration damper.