In the present analysis study, an analysis model was developed using ANSYS Workbench to verify the dynamic characteristics of the cabinet and the vibration reduction effect of applying TMD. The analysis modeled a simplified equivalent structure of a nuclear power plant cabinet, and a method was explored to reduce the cabinet's resonant response by installing TMD on top of the cabinet. For the analysis, harmonic loads and SSE seismic waves were input to conduct modal analyses of the cabinet and TMD. The cabinet vibration reduction effect of TMD installation was investigated, as well as the time histories of displacement and acceleration. The analysis results showed that the primary mode of the cabinet had a MPMR of approximately 53.9%, significantly affecting the dynamic behavior of the cabinet compared to other modes. However, a MPMR of approximately 8.9% was also observed in higher-order modes. With TMD installed, the peak response was significantly reduced, the larger curve split into two smaller curves, and the response at the original natural frequency was reduced by up to approximately 60%. The cabinet's time response showed a decrease in displacement/acceleration vibration response as the damping ratio increased. This indicates a narrow bandwidth and peak suppression of the response envelope, and the maximum displacement and acceleration reduction effects were approximately 33.1% and 27%, respectively.

In this study, we performed experiments aimed at improving the performance of circular Tuned Liquid Dampers (TLDs). TLDs offer numerous advantages over other passive vibration control devices. They are easy to install not only in new structures but also in existing ones, and they provide high cost efficiency compared to Tuned Mass Dampers (TMDs). Maintenance is straightforward, requiring only checks of the liquid level and inspections for any leakage. To adjust the natural frequency of a TLD for both installation and maintenance, we can simply manage the liquid level within the device. However, much of the existing research on enhancing TLD performance has focused on rectangular shapes. Therefore, we conducted experiments to investigate ways to achieve an improved damping ratio in circular TLDs equipped with internal dampers. A large number of shaking table experiments were carried out using various configurations of TLDs with dampers. We explored different arrangements of dampers and compared their performance against that of conventional TLDs.

This study was conducted to improve the stability of small barges used for remote bird monitoring at Capsosiphon fulvescens aquaculture farms. The monitoring accuracy is compromised by rolling and pitching motions induced by waves and wind. To address this problem, a damping system was developed to enhance barge stability. Field experiments were conducted at a farm to evaluate the effectiveness of the developed damping system. The rotational motions of the barge, with and without the damping system, were measured using a six-axis gyroscope sensor. The measurements were conducted at the Capsosiphon fulvescens farm located in Cheokchan-ri and Deokdong-ri, Gogeum-myeon, Wando-gun, Jeollanam-do across two periods: from October 5, 2024 to December 17, 2024 (Damping without) and from February 19, 2025 to April 15, 2025 (Damping with). The collected data were validated against wind speed records from the Korea Meteorological Administration. The results demonstrated that the damping system effectively reduced barge motion. Within a wind speed range of 0.1-9.0 m/s, the system achieved an average reduction of 7.11% in rotational motions. Its maximum performance was recorded at approximately 7.0 m/s wind speed where it achieved a reduction of 23.35%. These findings confirm the system significantly enhances barge stability and improves monitoring reliability.

This study analyzes how the damping characteristics of anisotropic magnetorheological elastomers (MREs) change according to magnetic flux density, the volume fraction of carbonyl iron powder (CIP), and pre-stress. MREs are intelligent materials whose mechanical properties change depending on the magnetic field, and while research on stiffness changes has been actively conducted, analysis of damping characteristics is relatively insufficient. Consequently, the damping characteristics of MREs showed nonlinear responses depending on the interaction among magnetic flux density, CIP volume fraction, and pre-stress, confirming that damping performance can be utilized as a controllable material parameter. These results suggest the possibility that, in the design of MRE-based vibration control systems, not only stiffness but also damping characteristics can be actively controlled, and they provide basic data for the future development of high-performance vibration reduction technologies.

Friction Stir Spot Welding (FSSW) is a solid-state welding technology that is rapidly growing in the automotive industry. Achieving superior welding characteristics requires the proper selection of tool geometry and process conditions. In this study, FSSW was performed on dissimilar materials comprising AA5052-HO/hot-melt aluminum alloy sheets and Steel Plate Cold Rolled for Deep Drawing Use(SPCUD) steel sheets. The effects of tool geometry, plate arrangement, and tool plunge depth on the welding process were investigated. At the joint interface between the aluminum alloy and the steel sheet, new intermetallic compounds (IMCs) were observed. As the plunge depth increased, thicker and more continuous IMC layers were formed. However, excessive plunge depth led to discontinuous layers and cracking defects. An analysis of the IMCs revealed a correlation between the IMC thickness and the shear tensile load. Furthermore, compared to the conventional Al-Top arrangement, the St-Top arrangement exhibited reduced deformation and superior shear tensile load values. These findings indicate that plate arrangement significantly influences the mechanical properties of the joint.

This study proposes a steel plate retrofit method and a polyurea method to improve the structural stability and usability of a factory floor slab with a thickness of 120mm. To assess vibration changes, vibrations were measured before and after retrofit. A numerical analysis model was also developed to evaluate improvements in structural safety and usability. The natural frequency increased from 11.4Hz to 17Hz through steel plate reinforcement, confirming an increase in slab stiffness. The damping ratio increased from 2.3% to 3.2% with polyurea reinforcement, indicating improved vibration reduction. Additionally, numerical analysis modeling showed that the natural frequency increased from 13.9Hz to 16.2Hz due to the steel plate reinforcement, enhancing the dynamic characteristics of the floor slab and confirming the reliability of the analysis model.

건축 토목 구조물에 작용하는 하중은 알 수 없는 경우가 대부분이므로 구조물에 대한 시스템 식별 알고리듬은 외부하중을 백 색잡음으로 가정한다. 이러한 가정은 일면 타당성이 있으나 와류하중과 같이 스펙트럼이 특정한 형태를 가지고 있는 경우 모달 파라 미터 특히 감쇠비 추정의 불확실성의 원인이 되고 있다. 본 연구에서는 구조물의 응답으로부터 역 계산된 하중을 이용하여 하중모델 을 구축하고 이를 이용하여 감쇠비를 추정하는 새로운 기법을 제안한다. 본 제안 기법은 외부하중을 백색잡음으로 가정하는 기존 VDS 기법을 기반으로 외부하중 스펙트럼 모델을 고려할 수 있는 보다 일반화된 기법이다. 제안된 추정기법을 직사각형단면 공탄성모델에 대한 공기력진동실험으로 수행하여 구한 가속도 응답에 적용하여 감쇠비추정의 신뢰성을 검증하였다. 풍속에 따라 풍하중 모델을 구 축하고 와류공진, 와류공진 전 후의 공력감쇠비를 평가한 결과 안정적이며, 신뢰도가 높은 감쇠비 추정이 가능함을 알 수 있었다.

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.