• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.191-198
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• 2003

Flat slab system has been adopted in many buildings constructed recently because of the advantage of reduced floor heights to meet the economical and architectural demands. Structural engineers commonly use the equivalent frame method(EFM) with equivalent beams proposed by Jacob S. Grossman in practical engineering for the analysis of flat slab structures. However, in many cases, when it is difficult to use the EFM, it is necessary to use a refined finite element model for an accurate analysis. But it would take significant amount of computational time and memory if the entire building structure were subdivided into a finer mesh. An efficient analytical method is proposed in this study to obtain accurate results in significantly reduced computational time. The proposed method employs super elements developed using the matrix condensation technique and fictitious beams are used in the development of super elements to enforce the compatibility at the interfaces of super elements. The stiffness degradation of flat slab system considered in the EFM was taken into account by reducing the elastic modulus of floor slabs in this study. Static and dynamic analyses of example structures were peformed and the efficiency and accuracy of the proposed method were verified by comparing the results with those of the refined finite element model and the EFM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.58-65
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• 2019

Polymer concrete is expected to be widely used as a building material because it has a shorter hardening time and excellent compression, tensile, bending, bond strength, frictional resistance and abrasion loss compared to general concrete. The polymer concrete has excellent vibration damping performance and research on the use of various reinforcing materials is being conducted. However, in order to completely replace the general concrete and the general anti-vibration reinforcement, such polymer concrete requires an overall review of vibration reduction performance considering physical properties, dynamic properties, productivity and field applicability. In this study, the physical and dynamic properties of polymer concrete by epoxy mixing ratio were compared with those of general concrete. It was appeared that compression, tensile, bending and bond strengths of polymer concrete by epoxy mixing were significantly higher than those of general concrete. Especially, the tensile strength was more than 4 ~ 6.5 times. Based on the basic physical properties of polymer concrete, the damping ratio, which is a dynamic characteristic according to the epoxy mixing ratio, was derived through analytical models and experiments. As a result, the dynamic stiffness of polymer concrete was 20% higher than that of general concrete and the loss rate was about 3 times higher.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.694-702
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• 2017

In the case of an elevated railway station, structure borne noise and vibration due to structural limitations allow the load and vibration from railway vehicles to be directly transmitted to the station structure, resulting in an increase in the number of civil complaints from customers and staff of the station. The floating slab track system, which is well known as one of the solutions for reducing the noise and vibration from elevated railway stations, usually contains rubber mounts or rubber pads under the railway slab which act as a damper. These types of device have the disadvantage that is difficult to predetermine the exact stiffness and damping ratio under the nonlinear loads resulting from train services. In this study, an isolator with a friction type of wedge is introduced, which can be applied to floating slab track systems and to be designed with precisely the required stiffness. Furthermore, a comparative analysis of the stiffness between the designed and experimental values is carried out, while the damping ratio, which is closely related to the friction wedge blocks, is deduced according to the train load condition. The performance tests of the isolator were conducted in accordance with the DIN 45673-7 standard which includes both static and dynamic load tests. The load conditions for the performance tests are designed to conform to the DIN standard related to the weight of the train and rail track, in order to perform vertical and horizontal load tests, so as to ensure the secure structural safety of the railway. Also, by checking the change aspect of the friction coefficients of the friction elements according to the loading rate, the vibration reduction performance of the friction type isolator with variable loading rate conditions is examined.

• Journal of the Society of Disaster Information
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• v.15 no.2
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• pp.292-300
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• 2019

Purpose: To reduce the noise and vibration of reinforced concrete slab structures, the damping performance is to be performed experimentally after installing hollow core or filling it with liquid. Method: Using the hollow rate as an experimental variable, the damping ratio and stiffness of each test specimen at impact load are obtained to determine the difference between the damping ratio and stiffness of the numerical analysis. In addition, the damping effects are reviewed by comparing the difference in the damping ratio and stiffness of a test specimen filled with liquid 50% of the study. Results: Since the difference in resistance between a specimen with or without hollow core is 5%, it is judged that there is no structural problem, and the injection of liquid into the hollow core can increase the damping ratio, which can reduce noise or vibration. Conclusion: At less than 20% of hollow rate, there was little damping effect, and at 30%, damping effect was found. However, if liquid is injected into the hollow core of the specimen, damping rate is shown to increase, and the injection of liquid into the hollow part is believed to reduce noise or vibration.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1155-1157
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• 2011

본 논문에서는 가전기기의 대기전력 저감을 위해 Capacitive Divider Power Supply(CDPS)로 전원을 공급받는 고효율 전원제어회로를 제안하였다. 이 제어회로는 220 V의 AC 전압을 높은 효율로 기기의 구동용 저전압 DC로 변환하기 위하여 기존의 변압기나 SMPS를 사용하는 대신 커패시터 분압기(Capacitive Divider)를 사용하여 전원을 공급하도록 제작되었으며, 대기 상태에서 교류전력선과 가전기기를 완전히 분리시킨 상태에서 적외선 수신기, MCU, 래치 타입 릴레이 등의 소자를 이용하여 기존 상용 리모컨으로도 전원제어가 가능하도록 설계되었다. 설계된 회로의 소비전력은 2.2 mW이며 본 논문에서 제안한 전원제어회로를 대기전력이 700 mW인 모니터에 적용하여 측정한 결과 대기전력이 7 mW로 낮아지는 것을 확인하였으며, 태양전지를 보조전원으로 추가 할 경우 태양전지에서 공급해주는 전력만큼 대기전력이 감소함을 확인하였다.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.133-138
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• 2008

In this study, the seismic behavior of arch structure with lead rubber bearing(LRB) is analyzed. The arch structure is the simplest structure and has the basic dynamic characteristics among large spatial structures. Also, Large spatial structures have large vertical response by horizontal seismic vibration, unlike seismic behavior of normal rahmen structures. When horizontal seismic load is applied to the large spatial structure with isolation systems, the horizontal acceleration response of the large spatial structure is reduced and the vertical seismic response is remarkably reduced.

• Journal of Korean Association for Spatial Structures
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• v.9 no.4
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• pp.97-103
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• 2009

The seismic isolation system reduces the seismic vibration that is transmitted from foundation to upper structure. This seismic isolation system can be classified into base isolation and mid-story isolation by the installation location. In this study, the seismic behavior of arch structure with mid-story isolation is analyzed to verify the effect of seismic isolation. Mid-story isolation is more effective than base isolation to reduce the seismic responses of roof structure. Also, this isolation would be excellent in structural characteristics and construction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.113-117
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• 1996

구조물의 진동에 의해 소음이 방사되는 현상은 기계에서 소음의 발생원으로 볼 수 있기 때문에 기게류의 소음을 예측하거나 저감방안을 제시하기 위해서는 구조물의 동특성과 방사특성을 이해하고 있어야 한다. 특히, 엔진블럭, 펀치프레스, 배의 갑판구조물등과 같은 대다수의 소음 발생기계는 평판의 형상을 가진 구조물로서 기계적인 충격 등에 의해 그 표면에서 소음이 발생되므로 강성을 증가시키고, 소음저감을 목적으로 빔과 같은 보강재를 통해 보강되어 있다. 그런데, 해석적인 방법으로는 평판이나 원판 또는 구와 같은 단순한 형태의 특정구조물에 대해서만 그 결과를 얻을 수 있으므로 이와 같은 불연속 평판구조물의 진동 및 방사특성은 평판에 대한 순수 이론으로는 해석이 곤란하여 따라서 본 연구에서는 수치해석적인 방법을 통해 이를 해결하고자 하였다. 수치해석적인 방법으로는 유한요소법(FEM)과 경계요소법(BEM), 및 통계적 에너지 해석기법(SEA)등이 있으며 구조물의 진동-소음연성문제의 경우에 있어서는, 진동해석을 FEM과 SEA으로, 공기 중에서의 방사현상은 BEM으로 예측하고 있다. 본 연구에서는 재질이 균일한 얇은 2차원 평판구조와 보강평판에 대해서 진동특성은 유한요소해석 프로그램을 사용하여 해석하였으며 이때의 진동특성값을 입력데이터로 사용하여 경계요소해석 프로그램으로 방사효율 등을 예측하였다. 또한 이 과정에서 2차원 평판구조의 모우드 밀도와 가진점 모빌리티의 실수값이 가지는 평균치의 물리적 특성을 분석하였으며, 추후 실험을 통해 이를 검증코자 한다.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.90-90
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• 2011

최근 전 세계적으로 지진의 발생 빈도가 증가하며 그 규모도 점차 커지는 경향을 보이고 있다. 대형지진의 발생 시 저층 구조물의 붕괴로 인한 인명 및 사회, 경제적 피해가 두드러짐에 따라 기존 저층 구조물의 내진보강기법에 관한 연구가 활발히 진행 중인 추세이다. 우리나라의 경우 강도증가형 내진보강공법이 주를 이루고 있어 다양한 내진보강기법의 개발 및 적용이 필요한 실정이다. 따라서 본 연구에서는 지진입력하중 저감형 내진보강기법으로서 강재댐퍼시스템을 제안하여 구조적 성능을 파악하고, 이를 적용한 보강 실험체와 비보강 실험체를 제작하여 정적가력실험을 통하여 그 성능을 비교하였다. 제안된 강재댐퍼시스템은 입력에너지를 소산시키는 내부의 슬릿형 댐퍼와 이를 지지하는 기둥 및 외부 프레임으로 구성되며, 내부 댐퍼는 먼저 항복하여 에너지를 소산시키기 위하여 지지기둥 및 프레임에 사용된 강재보다 강성 및 강도가 적게 계획되었다. 강재댐퍼의 성능실험 결과, 비교적 안정적 거동을 하며, 강성과 강도 및 에너지 흡수능력이 우수하게 나타났다. 보강 및 비보강 실험체의 골조는 기존 학교 건축물의 표준도면을 기준으로 하여 골조의 일부를 대상으로 60% 축소율을 적용하여 계획하였으며, 보강 실험체는 미리 제작된 강재댐퍼시스템을 골조 내에 설치하여 에폭시 주입법으로 부착시공 하였다. 보강 및 비보강 골조 실험체의 정적가력 실험결과 비보강 실험체는 기둥의 휨 항복 후 변형의 증가에 따라 휨 및 전단 균열이 증가하면서 최종적으로 기둥이 전단파괴 되었으며, 보강 실험체는 비보강 실험체에 비하여 기둥 및 보의 균열이 적고, 골조에 골고루 분포되어 파괴 규모가 감소하였다. 최대 강도면에서 보강 실험체는 비보강 실험체에 비하여 약 3.4배 우수하였으며, 초기강성은 약 7배 가량 유리한 것으로 평가되어 제안된 강재댐퍼시스템이 강도면에서 우수한 성능을 나타냄을 알 수 있었다. 또한 두 실험체의 기둥 주근 및 띠철근의 변형률을 비교한 결과, 비보강 실험체는 대부분의 철근이 항복하여 큰 변형을 일으킨 반면, 보강실험체에서는 철근의 항복현상이 나타나지 않았고 댐퍼가 항복을 하면서 큰 변형을 일으켰다. 이를 통해 지진하중 입력 시 댐퍼에서 입력 에너지를 흡수하여 큰 하중을 부담하며, 기존의 구조부재에는 입력 에너지가 낮아 손상이 보다 적게 발생함을 확인하였다.

• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.641-646
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• 2002

A new damage detection technique using static displacement data was developed, in order to assess the structural integrity of bridge structures. In conventional damage assessment techniques using dynamic response, the variation of natural frequencies is intrinsically insensitive to the damage of the bridge: thus, it is usually difficult to obtain them from the measured data. The proposed detection method enables the estimation of the stiffness reduction of bridges using the static displacement data that are measured periodically, without requiring a specific loading test. Devices such as a laser displacement sensor can be used to measure static displacement data due to the dead load of the bridge structure. In this study, structural damage was represented by the reduction in the elastic modulus of the element. The damage factor of the element was introduced to estimate the stiffness reduction of the bridge under consideration. Likewise, the proposed algorithm was verified using various numerical simulations and compared with other damage detection methods. The effects of noise and number of damaged elements on damage detection were also investigated. Results showed that the proposed algorithm efficiently detects damage on the bridge.