• Smart Structures and Systems
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• 제20권2호
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• pp.231-246
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• 2017

A recent work by the authors has demonstrated the feasibility of scour evaluation for Kao-Ping-Hsi Cable-Stayed Bridge simply based on ambient vibration measurements. To further attain the goal of scour monitoring, a key challenge comes from the interference of several environmental factors that may also significantly alter the pier frequencies without the change of scour depth. Consequently, this study attempts to investigate the variation in certain modal frequencies of this bridge induced by several environmental factors. Four sets of pier vibration measurements were taken either during the season of plum rains, under regular summer days without rain, or in a period of typhoon. These signals are analyzed with the stochastic subspace identification and empirical mode decomposition techniques. The variations of the identified modal frequencies are then compared with those of the corresponding traffic load, air temperature, and water level. Comparison of the analyzed results elucidates that both the traffic load and the environmental temperature are negatively correlated with the bridge frequencies. However, the traffic load is clearly a more dominant factor to alternate the identified bridge deck frequency than the environmental temperature. The pier modes are also influenced by the passing traffic on the bridge deck, even though with a weaker correlation. In addition, the variation of air temperature follows a similar tendency as that of the passing traffic, but its effect on changing the bridge frequencies is obviously not as significant. As for the effect from the alternation of water level, it is observed that the frequency baselines of the pier modes may positively correlate with the water level during the seasons of plum rains and typhoon.

• 지구물리와물리탐사
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• 제8권2호
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• pp.119-128
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• 2005

하천에서 발생하는 세굴 과정을 파악하기 위해서 교량 우물통 주변의 침식 그리고 퇴적 양상을 조사하는 것은 필수적이다. 지구물리탐사법은 하천 하상변화를 파악하는데 매우 효과적이며, 과거에 발생한 하상의 세굴 현상을 이해하는데 도움을 줄 수 있다. 본 연구에서는 비파괴 지구물리탐사법인 지하 투과 레이다(Ground Penetrating Radar, GPR)를 이용하여 2002년 6월과 2002년 10월에 한강 내의 교각 주변을 대상으로 홍수전$\cdot$후 세굴에 의한 하상 변화,세굴과 되메움의 범위 및 깊이, 그리고 하상 매질을 조사하였다. 자료획득에는 100 MHz와 400 MHe안테나를 이용한 GSSI SIR 2000 시스템이 사용되었다. 하천의 흐름방향으로 조사한 24개의 교각 사이와 5개 교각의 주위를 돌며 획득된 GPR영상이 비교 제시되었다. 적절한 현장탐사장비와 탐사 절차가 적용된 GPR탐사는 교각 및 교대 주변의 하천 수심과 하상 지질학적 구조를 결정하는데 효과적일 수 있다는 결론을 얻었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.553-554
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• 2009

광섬유센서 등과 같은 정밀온도센서를 이용하여 기온, 수온 및 수중 지표면 온도를 측정하고, 각각의 온도 변화에 대응하여 교량 세굴 및 수위를 파악할 수 있는 계측시스템을 개발하고 이를 소개한다. 온도계측을 통한 교량 세굴 및 수위 측정 방법은, 온도를 측정할 수 있는 센서를 수중 지표면을 기준으로 일정깊이와 높이로 설치하여 각각의 위치에 따른 온도 변화량을 분석하여 세굴량을 추정하는 시스템이며, 센서를 교각 상부까지 연장할 경우 수심 측정까지도 가능한 방법이다.

• 한국해양공학회지
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• 제15권2호
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• pp.33-38
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• 2001

The subsidence characteristics of artificial reef (AFR) in the unsteady flow such as tidal flow were investigated. The scour and subsidence characteristics were confirmed in the steady flow field. In a main study, the interaction of "Flow - Sediment Movement - Structure Behavior" and scou $r_sidence mechanism were discussed int he unsteady flow field. AFR subsidence characteristics was discussed with Reynolds number(Re*), Shields number(Sn*), dimensionless acceleration of flow (af/g) and dimensionless time (t/T). Most of all, the continuous AFR subsidence from the scour was occurred by periodic behavior of AFR. This behavior is result from the asymmetric ground, and is influenced by maximum velocity, duration time and direction of flow.ow.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.55-62
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• 2003

This study considered the effect of scour depth on the behaviour of pile foundation of bridge structure under seismic excitation. The numerical model was composed of the superstructure, pile foundation and soil. The superstructure and pile was modeled by beam elements and soil was by spring elements. The pile head and concrete footing was considered as hinge and rigid connected situation, respectively. A toro-gap element was used to model the expansion joint of superstructure. Nonlinear dynamic analysis was carried out on the constructed model. It was acknowledged that the steel pile become to yield after the scour depth reached about 2.0m.

• Water Engineering Research
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• 제3권3호
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• pp.155-162
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• 2002

This study presents the theoretical approach for volume concentration, velocity profile, and granular discharge on the fluid-granule mixed flow downstream of the scour hole at the outlet of the hydraulic structure. Concept of dilatant model was applied for the stress-strain relationships of fluid-granule mixed flow since the flow downstream of the scour hole corresponds to debris flow, where momentum transfers through particle collisions. Mathematical formulations were derived using momentum equation and stress-strain relation of the fluid-granule mixture. Velocity profile under the assumption of uniform concentration over flowing layer showed the downward convex type. Deposition angle of downstream hump was found to be a function of an upstream slope angle, a dynamic friction angle and a volume concentration irrespective of flow itself, Granular discharge and the overflow depth were obtained with given values of inflow rates. Experimental results showed relatively good agreements with theoretical ones.

• 한국구조물진단유지관리공학회 논문집
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• 제10권1호
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• pp.216-222
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• 2006

본 연구는 교각의 형상에 따라 교량하부구조물에 미치는 영향에 관한 연구이다. 유수의 흐름에 의해 교각 주위에서의 하상재료가 침식, 운반, 퇴적작용을 하여 이에 따라 수로의 하상단면은 변화를 하게 된다. 본 연구에서는 흐름과 동일한 방향으로 설치된 일련연속교각에서 교각의 형상변화에 따른 국부세굴 특성을 BOSS SMS로 통하여 분석하였다.

• 한국안전학회지
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• 제32권4호
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• pp.34-39
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• 2017

Typical flow regime of overflow at barrier or weir constructed in mid and small streams becomes as the submerged flow during most flood events. One of major causes of barrier failure has been reported as the levee-scour near the conjuction node between barrier and levee. However, most related design guidelines in Korea have not mentioned about the protection of levee around barrier or weir in detail. Furthermore, most previous researches have focused on the flow characteristics of overflow around several types of weirs but they did not have considered the material properties of levee itself. In this study, local scour near barrier was investigated with different material properties of levee under the submerged overflow condition which is assumed to reenact a flood event. Based on results from Fritz et al. and Mavis et al., a theoretical formula was also proposed in initial stage of laboratory experiments. And hydraulic experiments were carried out for the verification of the proposed formula. Levee was installed in the prismetic trapezoidal open channel and most parts were made of concrete except for movable section in which scour was expected to occur for the efficiency of experimental procedure. Each compaction of movable section in levee was followed by the basis of the KS F 2312. Further, after performing the experiments to find the optimum water content for each sediment, the specific amount of water was injected before flowing water. The difference between the proposed theoretical formula and experiment results was not much but considerable, which might be caused by the effect of compaction. For theoretical approach, it seemed that the formula did not take into account the compaction of levee, thus the correction coefficient for levee compaction determined in the literature was considered. Finally, the formula for the length of scour around barrier or weir was proposed, which can be useful to predict a levee in the reference design of revetment in mid and small streams. As shortly future study, scour length of levee around barrier or weir under different flow conditions such as perfect overflow condition will be studied and it will be able to contribute to suggest the design formula or criteria under all overflow conditions near barrier or weir.

• 대한토목학회논문집
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• 제39권2호
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• pp.297-306
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• 2019

개수로 만곡부에서 흐름은 원심력이 작용하기 때문에 횡방향 수면경사가 나타나고 유심선은 만곡 외측으로 치우친다. 수중 수제는 만곡부의 다양한 공학적인 문제를 해결하는 데 사용될 수 있다. 수중 수제가 흐름방향과 이루는 입사각과 수제 열 간격이 만곡부의 하상변동과 편수위에 미치는 영향을 파악하기 위해서 $90^{\circ}$만곡 직사각형 단면 수로에 잔자갈을 깔고 이동상 수리실험을 하였다. 만곡부에 수중 수제를 설치하면 최대 세굴심은 증가하나 균일한 둔각으로 수제를 설치하면 세굴을 줄일 수 있다. 수제를 설치한 만곡부에 수제설치 기준하상의 형성유량과 같은 유량이 흐를 경우 최대 세굴이 발생하는 위치가 하류로 이동하고 편수위는 증가한다. 그 유량보다 작으면 최대 세굴심의 위치가 상류로 이동하며 편수위는 감소한다. 만곡부에서 수중 수제는 입사각, 유량, 수제 열 간격의 상호작용에 따라 하상변동과 편수위에 대한 영향이 다르다.

• 월간 양돈
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• 제17권11호통권195호
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• pp.147-152
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• 1995