• 복합신소재구조학회 논문집
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• 제4권4호
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• pp.30-36
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• 2013

Partially earth anchored (PEA) can improve the structural safety and economic feasibility of multiple span cable stayed bridge (CSB). The PEA-CSB can restrain axial compressive load acting on a tower and reduce the global buckling length of a stiffened girder. For these reasons, structural members subject to axial forces can be effectively utilized and material quantity required for a steel deck can be reduced to save construction cost. In this study, the PEA system was verified for its application on a multiple span CSB. The CSB is a four-tower multi-span bridge which has a main span length of 500 m. As high tensile stress was generated at the top of the bridge decks at the mid-span between two main columns, a hybrid deck system for enhancing the bridge deck sections was proposed. While the composite sections made of concrete and steel were used near to the main columns, steel sections were used at the mid-span between two main columns.

• Structural Engineering and Mechanics
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• 제58권2호
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• pp.327-345
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• 2016

Many experimental and analytical studies have been conducted with beam-column subassemblages composed of a two-span beam to investigate the progressive collapse resistance of RC frames. Most study results reveal a strength-decreased transition phase in the nonlinear static load-deflection curve, which may induce dynamic snap-through response and increase the chord rotation demand for effective catenary action (ECA). In this study, the nonlinear static response is idealized as a piecewise linear curve and analytical pseudo-static response is derived for each linearized region to investigate the rotation demands for the ECA of the two-span RC beams. With analytical parameters determined from several published test results, numerical analysis results indicate that the rotation demand of 0.20 rad recommended in the design guidelines does not always guarantee the ECA. A higher rotation demand may be induced for the two-span beams designed with smaller span-to-depth ratios and it is better to use their peak arch resistance (PAR) as the collapse strength. A tensile reinforcement ratio not greater than 1.0% and a span-to-depth ratio not less than 7.0 are suggested for the two-span RC beams bridging the removed column if the ECA is expected for the collapse resistance. Also, complementary pseudo-static analysis is advised to verify the ECA under realistic dynamic column loss even though the static PAR is recovered in the nonlinear static response. A practical empirical formula is provided to estimate an approximate rotation demand for the ECA.

• Wind and Structures
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• 제8권2호
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• pp.89-106
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• 2005

For estimating the vortex excited vibrations of overhead transmission lines, the Energy Balance Principle (EBP) is well established for spans damped near the ends. Although it involves radical simplifications, the method is known to give useful estimates of the maximum vibration levels. For very long spans, there often is the need for a large number of in-span fittings, such as in-span Stockbridge dampers, aircraft warning spheres etc. This adds complexity to the problem and makes the energy balance principle in its original form unsuitable. In this paper, a modified version of EBP is described taking into account in-span damping and in particular also aircraft warning spheres. In the first step the complex transcendental eigenvalue problem is solved for the conductor with in-span fittings. With the thus determined complex eigenvalues and eigenfunctions a modified energy balance principle is then used for scaling the amplitudes of vibrations at each resonance frequency. Bending strains are then estimated at the critical points of the conductor. The approach has been used by the authors for studying the influence of in-span Stockbridge dampers and aircraft warning spheres; and for optimizing their positions in the span. The modeling of the aircraft warning sphere is also described in some detail.

• 컴퓨터교육학회논문지
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• 제5권4호
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• pp.53-60
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• 2002

GSP와 같은 Apriori-like 순차패턴 마이닝 방법들은 마이닝 과정에서 많은 후보패턴들을 생성하고, 대용량 데이타베이스의 반복적인 탐색을 필요로 하는 문제점이 있다. 그리고 후보패턴들의 탐색공간을 줄이기 위해 단계별로 프레픽스-프로젝티드 (prefix-projected) 데이터베이스를 구성하는 PrefixSpan 방법은 탐색공간을 줄이지만 프로젝티드 데이터베이스의 구성비용이 문제가 된다. 효율적인 순차패턴 마이닝을 위해서는 후보패턴의 생성비용과 탐색공간을 모두 줄여야 한다. 본 논문에서는 이를 위한 새로운 순차패턴 마이닝 방법인 SuffixSpan(Suffix checked Sequential Pattern mining)을 설명하고, 이에 대한 형식적 접근을 보인다.

• Smart Structures and Systems
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• 제20권2호
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• pp.197-205
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• 2017

The dynamic performance of railway bridges under high-speed trains draws the attention of bridge engineers. The vibration issue for long-span bridges under high-speed trains is still not well understood due to lack of validations through structural health monitoring (SHM) data. This paper investigates the correlation between bridge acceleration and train speed based on structural dynamics theory and SHM system from three foci. Firstly, the calculated formula of acceleration response under a series of moving load is deduced for the situation that train length is near the length of the bridge span, the correlation between train speed and acceleration amplitude is analyzed. Secondly, the correlation scatterplots of the speed-acceleration is presented and discussed based on the transverse and vertical acceleration response data of Dashengguan Yangtze River Bridge SHM system. Thirdly, the warning indexes of the bridge performance for correlation scatterplots of speed-acceleration are established. The main conclusions are: (1) The resonance between trains and the bridge is unlikely to happen for long-span bridge, but a multimodal correlation curve between train speed and acceleration amplitude exists after the resonance speed; (2) Based on SHM data, multimodal correlation scatterplots of speed-acceleration exist and they have similar trends with the calculated formula; (3) An envelope line of polylines can be used as early warning indicators of the changes of bridge performance due to the changes of slope of envelope line and peak speed of amplitude. This work also gives several suggestions which lay a foundation for the better design, maintenance and long-term monitoring of a long-span high-speed bridge.

• 한국철도학회논문집
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• 제8권5호
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• pp.398-404
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• 2005

In this paper, we introduce the on-line test of the current collection characteristics for HSR 350x(Korea High Speed Train project) that have been performed in the Kyoung-bu high-speed line since 2002. Through the analysis of measured data during on-line test, the variation trend of contact force between pantograph and contact wire of catenary according to the span type, the track conditions and driving patterns is reviewed. In order to analyze the variation trend of contact force, we have checked the span type of catenary in KP 24 - 125 out of Kyoung-bu high speed line and obtained the statistical processing result per each span type. This study shows that the track conditions do not affect on the dynamic performance between pantograph and contact wire catenary, and the span type and the driving pattern are important factors in determining the good interaction between them.

• 한국측량학회지
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• 제28권3호
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• pp.377-383
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• 2010

본 연구의 목적은 GPS를 이용하여 장대교량의 거동을 실시간으로 모니터링 할 수 있는 시스템을 구축하는데 있다. GPS 센서를 이용하여 장대교량의 실시간 변위를 계측함으로써 장대교량의 3차원적인 거동이 분석 되어지고 관리될 수 있다. 본 연구에서 개발한 장대교량의 실시간 거동 모니터링 시스템은 통합운영센터로 교량의 수평 및 수직 방향 변위와 위험신호를 실시간으로 전송함으로써 장대교량의 안전관리를 가능하게 한다. 또한 GPS를 이용한 장대교량의 절대적 거동을 모니터링하고 전국적인 교량 안전관리네트워크를 구축하는데 활용할 수 있을 것이다.

• 한국농공학회지
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• 제35권4호
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• pp.76-85
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• 1993

The purpose of this study was to analyze the wind force distribution on the two single-span arched plastic house depending upon the house spacing and wind direction, which may provide the fundamental criteria for the structural design. In order to specify the wind force distribution, the variation of the wind force coefficients, the mean wind force coefficients and the drag force coefficients were estimated from the wind tunnel test data. The results obtained are as follows : 1. At the wind direction of 90$^{\circ}$, there was a typical span interval at which the maximum negative pressure was occured at the edge of the inside walls. 2. In the consideration of wind loads, the wind force coefficients estimated from independent single-span arched plastic house should not be directly applied to the structural design on the double houses separated. 3. The average maximum negative wind force on the inside walls was occured at the wind direction of 90$^{\circ}$, and the variations depending on the span intervals was not significant. 4. The average maximum drag force was occured at the wind direction of 300, and the magnitude of drag force was more significant at the first house. As the distance between two houses was increased, the drag force was slightly increased for every wind direction.

• 터널과지하공간
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• 제15권5호
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• pp.369-377
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• 2005

지하공동의 안정성은 생산성과 안전을 확보해야 하는 광산의 운영에 있어서 가장 중요한 관심사이다. 암반분류는 많은 경험적인 설계방법의 근간을 이룰 뿐만 아니라 수치해석을 위한 기초자료로 이용되고 있다. 공동의 안정성에 영향을 주는 많은 요소들 중 주어진 암반의 조건 중에서 공동폭은 하나의 중요한 설계요소가 된다. 이 논문에서는 Lug에 의해 제안된 한계 공동폭 기준, Mathews stability graph method 그리고 저자들에 의해 제안된 한계 공동폭 기준을 비교하였다. Methews stability graph method를 이용하여 저자들에 의해 수정된 한계 공동폭 기준을 제안하였고 이것을 여러 석회석 광산 지하공동의 안정성을 평가하는 데 사용하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.668-673
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• 1998

The specimen of current study has the same type with the 3-span slabs of Burns et al used in the study by Mojtahedi/Gamble, which laid a ground for the revision of the ACI318-77 code to the ACI 318-83 code. But those specimens was failed prematurely before it reached the ultimate strength which the specimen had. The reason is that bonded reinforcements were cut off where there is no need for the flexural reinforcement. As results. the slabs failed ultimately where the reinforcements was cut off. Thus, the tendon stresses of failure may have been much smaller than the values which culd reach if the bonded reinforcements were extended beyond the theoretical cut off points. On the based on the fact mentioned above. the specimens which had the same conditions as the specimens of Burns et al were used in the current study, but in which the reinforcements were distributed in a sequence for the reinforcements not to be cut anywhere in the 3-span. As a results, it was known that the current ACI code, revised by the result of Mojtahedi/Gamble's study, overestimated the effect of span/depth ratio on the members with high span/depth ratio. Thus it was concluded that the effect of span/depth ratio on the ultimate stress of unbonded tendon regulated by the current ACI code must be reconsidered and reevaluated.