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 the case of a school building, even though it is a regular structure in terms of plan shape, if the masonry infill wall acts as a lateral load resisting element, it can be determined as a torsionally irregular building. As a result, the strength and ductility of the structure are reduced, which may cause additional earthquake damage to the structure. Therefore, in this study, a structure similar to a school building with torsional irregularity was selected as an example structure and the damping performance of the PC-BRB was analyzed by adjusting the eccentricity according to the amount of masonry infilled wall. As a result of nonlinear dynamic analysis after seismic reinforcement, the torsional irregularity of each floor was reduced compared to before reinforcement, and the beams and column members of the collapse level satisfied the performance level due to the reduction of shear force and the reinforcement of stiffness. The energy dissipation of PC-BRB was similar in the REC-10 ~ REC-20 analytical models with an eccentricity of 20% or less. REC-25 with an eccentricity of 25% was the largest, and it is judged that it is effective to combine and apply PC-BRB when it has an eccentricity of 25% or more to control the torsional behavior.

This study proposes an RCS composite damping device that can achieve seismic reinforcement of existing buildings by dissipating energy by inelastic deformation. A series of experiments assessing the performances of the rubber core pad, hysteretic steel slit damping device, and hybrid RCS damping device were conducted. The results showed that the ratios of the deviations to the mean values satisfied the domestic damping-device conformity condition for the load at maximum device displacement in each direction, at the maximum force and minimum force at zero displacement, as well as the hysteresis curve area. In addition, three analysis models based on load-displacement characteristics were proposed for application to seismic reinforcement design. In addition, the validity of the three proposed models was confirmed, as they simulated the experimental results well. Meanwhile, as the shear deformation of the rubber-core pad increased, the hysteretic behavior of super-elasticity greatly increased the horizontal force of the damping device. Therefore, limiting the allowable displacement during design is deemed to be necessary.

It is effective to apply hybrid damping device that combine separate damping device to cope with various seismic load. In this study, HRS hybrid damper(hybrid rubber slit damper) in which high damping rubber and steel slit plate are combined in parallel was proposed and structural performance tests were performed to review the suitability for seismic performance. Cyclic Loading tests were performed in accordance with criteria presented in KDS 41 17 00 and MOE 2019. As a result of the test, the criteria of KDS 41 17 00 and MOE2019 was satisfied, and the amount of energy dissipation increased due to the shear deformation of the high-damping rubber at low displacement. Result of performing the RC frame test, the allowable story drift ratio was satisfied, and the amount of energy dissipation increased in the reinforced specimen compared to the non-reinforced specimen.

바람에 의한 구조물의 진동은 관심대상이 되는 지배모드의 감쇠비에 매우 민감하다. 감쇠비의 발현 메커니즘의 불확실성 등 에 의해 감쇠비의 추정은 여전히 도전과제이며 보다 정확한 감쇠비 추정을 위한 연구가 지속되고 있다. 본 연구에서는 스펙트럼 밀도 적분함수라는 새로운 개념을 이용하여 구조물의 감쇠비를 추정하는 기법을 다룬다. 모드 응답스펙트럼에 포함된 외부하중 스펙트럼을 적분에 의한 평균화효과에 의해 평탄화 한 후 이론적 적분함수와 비교하여 감쇠비를 구하는 원리이다. 감쇠비 추출 가능성 탐색을 위 해 이론적 스펙트럼 밀도 적분함수의 특성을 분석하였으며, 비고전감쇠 시스템이 가지는 혼성 모드응답에 적용할 수 있는 감쇠비 추 정법로 확장하였다. 본 연구에서 제안된 감쇠비 추정법을 검증하기 위한 수치해석과 계측응답에 대한 적용이 이루어졌으며, 검증결과 제안된 감쇠비 추정법이 안정적이며, 신뢰도가 높은 감쇠비 추정이 가능함을 알 수 있었다.

부공력감쇠는 풍직각방향의 와류공진을 예측하는데 있어서 매우 중요한 요소이다. 부공력감쇠는 진동유발하중 또는 피드백 하중을 구성하는 주요인자로 와류진동이 급격히 발현되는 현상을 설명하는 도구이기도 하다. 본 연구에서는 공력감쇠의 수학적 모델 을 제시하고 와류유발하중모델과 함께 와류진동을 예측하는 프러세스를 제안한다. 직사각형단면에 대한 공기력진동실험을 수행하여, 계측된 가속도로부터 공력감쇠와 와류유발하중을 추정하고 이에 기반하여 공력감쇠모델과 와류유발하중모델을 구축하는 과정을 다룬 다. 최종적으로 공력감쇠모델과 와류유발하중 모델에 대한 재해석을 통하여 가속도응답을 구하고 계측된 가속도와 비교하여 모델의 진동예측성능을 평가한다. 본 연구에서 제안된 와류하중모델의 진동예측성능을 평가한 결과 안정적이며, 신뢰도가 높은 와류진동예측 이 가능함을 알 수 있었다.

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.

풍방향 공력감쇠는 항상 정감쇠 형태로 나타나기 때문에 구조물 진동을 더욱 안정화하는 경향이 있다. 준정상 가정에 의하여 공력감쇠를 예측할 수 있는 이론적 모델은 풍방향 공력감쇠의 발현특성을 모사하고, 발현에 영향을 미치는 영향인자를 설명하고 있다. 본 연구에서는 공탄성 실험을 통해 얻어진 계측응답으로부터 추정된 풍방향 감쇠를 이론적 풍방향감쇠와 비교하여 준정상 가정으 로부터 구해진 이론적 모델의 정합성을 평가하였다. 풍방향 감쇠는 최신 개발된 시스템 식별기술인 가상동적가진기에 의한 방법을 이 용하여 구한다. 본 연구결과로부터 풍방향 공력감쇠는 준정상가정에 의한 이론적 모델과의 차이를 보이며, 이것은 주로 높이별, 평균 풍속에 따른 난류강도의 크기에 의하여 영향을 받는 것으로 나타났다.

The vibration control device such as the damper can be used to reinforce the seismic performance of structures. The damper is activated by the deformation of structures during earthquake; however, the deformation of structures is extremely small, causing difficulty in using the damper. Therefore, there is a need for a method capable of amplifying small deformities and transmitting them to the damper. The purpose of this paper is to develop and evaluate a displacement amplification seismic system using cable-pulley. The appropriate cable was selected through a cable tensile performance test and the results of the frame experiment were compared with theoretical displacement amplification ratio values. As a result, it may be said that the proposed system using cable-pulley is useful for displacement amplification.

Generally, vibration absorber systems are composed of spring-mass systems to reduce the vibration of a structure, and there are also methods to simply increase damping to achieve a damping effect across a wide frequency band. One similar method is to use a mechanism in which the eddy current is converted into a mechanical damping effect. When an eddy current is generated by electromotive force due to magnetic flux change, the reaction force is generated by the eddy current’s circulation. In this study, the damping system using the reaction force was constructed to reduce the transmission of vibrations generating from internal fluid and the vibration reduction characteristics that are transmitted externally were analyzed. As a result, 8.2 % of the vibration reduction effect from primary excitation frequency was confirmed.

Pipe for water supply is one of the important parts that supply water to home, factory and so on. Water leakage in pipe for water supply due to deterioration, ground sinking and earthquake leads to enormous economical loss. Therefore, pipe for water supply should be designed to satisfy the requirement of, for instance, structural stability and fatigue durability. The purpose of this study was to investigate the fatigue durability of flexible joint for relaxing the impact due to earthquake and ground sinking. For this purpose, flexible joint was simulated using dynamic characteristics and fatigue life. As the results, the problem of fatigue durability may occur when flexible joint and pipe for water supply are treated as rigid body in simulation. Thus it means that the role of packing in flexible joint is very important and packing should be designed as optimal conditions that are considered fatigue durability as well as waterproof.

The pipe for water supply is essential part among SOC (Social Overhead Capital) fields. Pipe for water supply is mainly damaged by deterioration of pipe, earthquake, ground sinking and so on. The leakage of water have been led to enormous economical loss in our country. The purpose of this study was to investigate the structural stability of flexible joint for relaxing impact due to earthquake and ground sinking. For this purpose, flexible joint was simulated using tensile load and internal pressure. As the results, flexible joint for structural stability was needed the tensile load of below 3 ton and internal pressure of below 60 kgf/cm2. However, it is considered that real flexible joint should be applied more high safety factor than that of simulation result because of combined stress.

Damping and sound absorption not only reduce environmental pollution caused by vibration and noise, but also improves processing accuracy, resolution of precision measuring instruments and fatigue life of machine parts in various precision machines. The vibration-damping plate is largely divided into a constrained type in which the resin is confined by a plate and a non-constrained type in which a plate is made of a polymer material mainly composed of polymer. The external vibration energy is absorbed by the thermal energy required for friction, stretching and compression of resin, so that the noise and vibration generated by resonance are reduced. The vibration damping ability of the sandwich plate produced in this study was found to be somewhat superior, which may be due to the difference in adhesive force during the manufacture of the sandwich plate. In the experimental results, it was confirmed that the sandwich plate material is superior to the vibration damping ability than the 5182 aluminum single plate material, it can be seen that the sandwich plate is effective for vibration damping of the aluminum alloy plate material.

This study investigates the effect of thermo-mechanical treatment on the damping capacity of the Fe-20Mn-12Cr- 3Ni-3Si alloy with deformation induced martensite transformation. Dislocation, αʹ and ε-martensite are formed, and the grain size is refined by deformation and thermo-mechanical treatment. With an increasing number cycles in the thermo-mechanical treatment, the volume fraction of ε-martensite increases and then decreases, whereas dislocation and α'-martensite increases, and the grain size is refined. In thermo-mechanical treated specimens with five cycles, more than 10 % of the volume fraction of ε-martensite and less than 3 % of the volume fraction of αʹ-martensite are attained. Damping capacity decreases by thermomechanical treatment and with an increasing number of cycles of thermo-mechanical treatment, and this result shows an opposite tendency for general metal with deformation induced martensite transformation. The damping capacity of the thermomechanical treated damping alloy with deformation induced martensite transformation greatly affect the formation of dislocation, grain refining and α'-martensite and then ε-martensite formation by thermo-mechanical treatment.

공력감쇠는 와류에 의한 풍직각방향의 응답을 평가하는데 매우 유용한 인자로 인식되어 왔다. 그러나 기존의 공력감쇠 산정 방식은 구조물 응답에 기반한 시스템 식별기술을 적용하는 것으로 와류하중속에 포함되어 있는 공력감쇠의 역할과 특성을 파악하는 데 한계를 가지고 있었다. 본 연구에서는 하중식별기술을 적용하여 와류하중을 직접적으로 구함으로써 와류하중을 구성하는 요소와 유발요인을 평가하고자 하였다. 이를 위하여 대기 경계층에서 원형 실린더 모델에 대한 공탄성 실험을 수행하여 풍직각방향 와류하중 을 추정하였으며 그로부터 공력감쇠의 특성을 분석하였다. 분석결과, 와류하중은 구조물 모달속도가 공력감쇠에 의해 풍하중으로 전 환되는 모달속도하중과 변동풍속에 의해 형성되는 순수 와류하중으로 구성되는 것으로 나타났다. 공력감쇠는 최상층 평균풍속에 의한 와류방출진동수가 구조물의 고유진동수에 근접하면서 부감쇠를 가지며 그 결과 총 감쇠가 작아져 응답증폭현상을 유발하는 것으로 파악되었다. 본 연구결과에 기초하면, 난류상태에서 와류하중 특성이 반영된 와류하중모델 구축이 가능할 것으로 사료되며, 구조물 풍직 각방향 진동을 보다 효과적으로 파악하는데 활용될 수 있을 것으로 사료된다.