• Steel and Composite Structures
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• 제32권1호
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• pp.67-77
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• 2019

Pushover analysis captures the behavior of a structure from fully elastic to collapse. In this analysis, the structure is subjected to increasing lateral load with constant gravity one. Neglecting the effects of the higher modes and the changes in the vibration characteristics during the nonlinear analysis are the main obstacles of the proposed lateral load patterns. To overcome these drawbacks, whereas some methods have been presented to achieve updated lateral load distribution, these methods are not precisely capable to predict the response of structures, precisely. In this study, a new method based on optimization procedure is developed to obtain a lateral load pattern for which the difference between the floor displacements of pushover and Nonlinear Dynamic Analyses (NDA) is minimal. For this purpose, an optimization problem is considered and the genetic algorithm is applied to calculate optimal lateral load pattern. Three special moment resisting steel frames with different dynamic characteristics are simulated and their optimal load patterns are derived. The floor displacements of these frames subjected to the proposed and conventional load patterns are acquired and the accuracy of them is evaluated via comparing with NDA responses. The outcomes reveal that the proposed lateral load distribution is more accurate than the previous ones.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.375-382
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• 2005

In this paper, a practical control method of wind-induced vibration of high-rise buildings is presented in the form of resizing algorithm. In the structural design process for high-rise buildings, the lateral load resisting system for the building is more often determined by serviceability design criteria including wind-induced vibration level. Even though many drift method have been developed in various forms, no practical design method for wind induced vibration has been developed so far. Structural engineers rely upon heuristic or experience in designing wind induced vibration. The performance of the proposed method is evaluated by comparing wind-induced vibration levels estimated both from approximate techniques and wind tunnel test.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1027-1033
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• 2000

This paper describes the characteristics of vibration of a hydraulic turbine mainly due to cavitation occurrence. The analysis of vibration spectra of the turbine shaft shows that hub vortex cavitation occurs in the downstream of the turbine runner, which is verified from coherence analysis between shaft vibration displacement and dynamic pressure at the draft tube. Even though acceleration level measured at the guide vane lever, which is usually used for evaluation of cavitations performance, is decreased during forced aeration, it is found from the analysis of dynamic pressure spectra that cavitation around runner blades still remains unchanged. It is also found that lateral vibration of the turbine shaft is mainly due to the hub vortex cavitation of the turbine runner.

• 한국소음진동공학회논문집
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• 제24권5호
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• pp.407-413
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• 2014

The diesel engine and reduction gear combination is one of the common propulsion system in a naval vessel. Since the diesel engine has torsional vibration caused by reciprocating motion of the mass and gas pressure force of the cylinder, high cycle torsional fatigue can be occurred. Therefore, ROK navy restricts the maximum stress of the propulsion shaft according to MIL G 17859D. In this paper, the root cause for the failure of the diesel engine and reduction gear connecting shaft occurred in typical naval vessel is investigated based on the measured bending and torsional moment according to MIL G 17859D procedure.

• 한국강구조학회 논문집
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• 제9권2호통권31호
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• pp.259-267
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• 1997

본 연구에서는 주 케이블에 횡방향 새그를 가진 자정식 현수교의 내풍안정성을 검토하기 위하여 풍동실험을 수행하고, 주형의 거동을 중심으로 그 결과를 분석하였다. 등류와 난류하에서 수행한 부분 모형 실험에서 가장 내풍안정성이 뛰어난 단면을 최종단면으로 선정하고, 전교 모형 실험을 통하여 검증하였다. 또한 차후 연구를 위한 플러터 계수를 측정하여 제시하였다. 교량의 사용성과 피로문제를 검토하기 위하여 버페팅 응답을 조사하였지만, 공학적 관점에서 만족할 만한 수준인 것으로 나타났다. 주형의 항력계수가 상당히 큼에도 불구하고 횡방향 변위가 매우 작게 나타났는데, 이는 주 케이블의 횡방향 새그가 주형의 변위를 구속하기 때문인 것으로 판단된다.

• 터널과지하공간
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• 제16권4호
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• pp.288-295
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• 2006

본 연구에서는 발파 및 지진발생으로 인한 횡방향 지반진동에 대하여 KTX 차량 및 부산지하철을 대상으로 주행안전성을 평가하였다. 이를 위하여 휠/레일 상호작용 해석 WERIA프로그램인 프로그램을 이용하여 철도차량의 동적거동을 시뮬레이션 하였다. 또한 횡방향 지반진동이 철도차량에 유발할 수 있는 차륜/레일간의 큰 상대변위를 고려하기 위하여 차륜/레일간 접촉면의 기하학적 형상과 크리프힘을 반영하였다. 입력하중은 국내의 내진규정 특성에 부합하는 인공지진과 공사중 발생하는 발파진동을 사용하였다. 해석 결과 차륜/레일간의 상대변위와 탈선계수를 산정하여 철도 차량의 주행안전성을 평가한 결과 탈선가능성은 없는 것으로 나타났다.

• 한국지진공학회논문집
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• 제17권2호
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• pp.79-88
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• 2013

Steel plate concrete (SC) composite structure is now being recognized as a promising technology applicable to nuclear power plants as it is faster and suitable for modular construction. It is required to identify its dynamic characteristics prior to perform the seismic design of the SC structure. Particularly, the damping ratio of the structure is one of the critical design factors to control the dynamic response of structure. This paper compares the criteria for the damping ratios of each type of structures which are prescribed in the regulatory guide for the nuclear power plant. In order to identify the damping ratio of SC shear wall, this study made SC wall specimens and conducted experiments by cyclic lateral load tests and vibration tests with impact hammer. During the lateral loading test, SC wall specimens exhibited large ductile capacities with increasing amplitude of loading due to the confinement effects by the steel plate and the damping ratios increased until failure. The experimental results show that the damping ratios increased from about 6% to about 20% by increasing the load from the safe shutdown earthquake level to the ultimate strength level.

• 한국정밀공학회지
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• 제30권10호
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• pp.1051-1059
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• 2013

In general, lateral ride comfort of railway vehicle is mainly influenced by a secondary suspension placed between the bogie and carbody. Higher operating speeds of train results in increased vibration of carbody, which has a negative impact related to the ride comfort. To solve this problem, researches to replace the conventional passive suspension with (semi)active technology in the secondary suspension of a railway vehicle have been carried out. The semi-active suspension using the magneto-rheological damper is relatively simpler system and has advantage in maintenance compared to the hydraulic type semi-active damper. This study was performed to reduce lateral vibration acceleration of carbody related to ride comfort of railway vehicles with a semi-active suspension system. The numerical analysis was conducted by replacing passive lateral damper with semi-active MR damper, and robust control with the MR damper was applied to the 1/5 scaled railway vehicle model.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.552-558
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• 2001

When operating lathe gear box which is equipped with geared transmission, it sometimes generates loud noise and excessive vibrations. In order to identify their causes, in this study, torsional and lateral vibration characteristics including critical speeds of the gear transmission system are firstly analyzed using lumped parameter models. Natural frequencies and mode shapes of the gear box structure are also analyzed by using the modal test. Furthermore, measured vibration and noise signals during operations are analyzed and compared with theoretical analysis results. After all, it is concluded that the primary cause of the excessive noise and vibrations is the resonance between gear meshing frequency including its side bands, the frequencies of shaft bending and torsional vibrations, and the natural frequencies of the gear box structure. Consequently the noise and vibration levels are greatly reduced by avoiding resonance between the natural frequencies and gear meshing frequencies through the rearrangement of the gears on the transmission shaft without any gear ratio change.

• Structural Engineering and Mechanics
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• 제30권6호
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• pp.651-664
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• 2008

The purpose of this study is to develop a rehabilitation technique for heavily earthquake damaged masonry buildings. A full scale one storey masonry building with window and door openings was manufactured and tested on the shock table by applying increased amplitude free vibration up to the point where heavy earthquake damage was observed. Damaged test building was rehabilitated with vertical and diagonal steel straps and then tested again. The effectiveness of improvements obtained by the rehabilitation technique was investigated. Steel straps improved the lateral strength and stiffness of masonry walls and limited the lateral displacement of building. Stability of the masonry walls were also improved by the steel straps. Steel straps reduced the natural period of the earthquake damaged masonry building and prevented the failure of the building at the same amplitude of free vibration.