• Structural Monitoring and Maintenance
• /
• 제1권4호
• /
• pp.371-392
• /
• 2014

Long-span cable-supported bridges are flexible structures vulnerable to unsymmetric loadings such as railway traffic and strong wind. The torsional dynamic response of long-span cable-supported bridges under running trains and/or strong winds may deform the railway track laid on the bridge deck and affect the running safety of trains and the comfort of passengers, and even lead the bridge to collapse. Therefore, it is eager to figure out the torsional dynamic response of long-span cable-supported bridges under running trains and/or strong winds. The Tsing Ma Bridge (TMB) in Hong Kong is a suspension bridge with a main span of 1,377 m, and is currently the world's longest suspension bridge carrying both road and rail traffic. Moreover, this bridge is located in one of the most active typhoon-prone regions in the world. A wind and structural health monitoring system (WASHMS) was installed on the TMB in 1997, and after 17 years of successful operation it is still working well as desired. Making use of one-year monitoring data acquired by the WASHMS, the torsional dynamic responses of the bridge deck under rail traffic and strong winds are analyzed. The monitoring results demonstrate that the differences of vertical displacement at the opposite edges and the corresponding rotations of the bridge deck are less than 60 mm and $0.1^{\circ}$ respectively under weak winds, and less than 300 mm and $0.6^{\circ}$ respectively under typhoons, implying that the torsional dynamic response of the bridge deck under rail traffic and wind loading is not significant due to the rational design.

• 대한토목학회논문집
• /
• 제5권3호
• /
• pp.85-93
• /
• 1985

1978년(年) NOAA/NASA의 SEASAT 위성(衛星) 고도계자료(高度計資料)를 이용(利用)한 동지나해(東支那海)의 해면변위(海面變位)를 연구(硏究)하기 위한 초기노력(初期努力)이 서술(敍述)되었다. SEASAT 운용기간중(運用期間中)의 동지나해(東支那海)의 두 태풍통과시기(颱風通過時期)를 선택(選擇)하여 공간적(空間的), 시간적(時間的) 변화도(變化度)가 큰 천해조석(淺海潮汐), 해일(海溢) 및 지구조석(地球潮汐)에 대한 고도계(高度計) 자료경정(資料更正)을 하였는 바 일련(一連)의 작업(作業)을 일관(一貫)된 고도계처리체계(高度計處理體系)를 수립(樹立)하여 수행(遂行)하였다. 초기결과I(初期結果)들이 제시(提示)되었으며 추후(追後)의 연구(硏究)에 대한 토의(討議)를 하였다. 본(本) 연구(硏究)는 추후(追後) 이용가능(利用可能)한 해양위성(梅洋衛星)의 고도계자료(高度計資料)를 철저(徹底)하게 이용(利用)하여 동지나해(東支那海)의 국지해양학적(局地海洋學的)인 특성(特性)을 규명(糾明)하기 위한 첫 시도(試圖)로서 수행(遂行)된 것이다.

• 대기
• /
• 제31권3호
• /
• pp.311-326
• /
• 2021

To improve the predictability of high-impact weather phenomena around Seoul, where a larger number of people are densely populated, KMA conducted the intensive observation from 22 June to 20 September in 2020 over the Seoul area. During the intensive observation period (IOP), the dropsonde from NIMS Atmospheric Research Aircraft (NARA) and the radiosonde from KMA research vessel Gisang1 were observed in the Yellow Sea, while, in the land, the radiosonde observation data were collected from Icheon and Incheon. Therefore, in this study, the effects of radiosonde and dropsonde data during the IOP were investigated by Observing System Experiment (OSE) based on Korean Integrated Model (KIM). We conducted two experiments: CTL assimilated the operational fifteen kinds of observations, and EXP assimilated not only operational observation data but also intensive observation data. Verifications over the Korean Peninsula area of two experiments were performed against analysis and observation data. The results showed that the predictability of short-range forecast (1~2 day) was improved for geopotential height at middle level and temperature at lower level. In three precipitation cases, EXP improved the distribution of precipitation against CTL. In typhoon cases, the predictability of EXP for typhoon track was better than CTL, although both experiments simulated weaker intensity as compared with the observed data.

• 한국위성정보통신학회논문지
• /
• 제3권1호
• /
• pp.48-54
• /
• 2008

최근 이상 기상현상의 증가와 함께 일기예보의 중요성은 점점 커져가고 있다. 본 논문에서는 특수한 기상 환경에서의 일기예보를 수행하기에 적합한 레이다 영상 분석 관측을 다룬다. 특히 2007년 봄의 황사와 2006년 강원도 지방에 집중호우를 일으킨 제3호 태풍 에위니아를 레이다 영상을 통해 분석하고자 한다. 우리 나라에서는 해마다 황사현상의 빈도와 농도가 증가하고 있으며, 집중호우를 동반한 태풍 때문에 큰 피해를 입고 있기 때문에 레이다 영상을 이용한 기상환경 분석은 점차 중요해 질 것으로 예측된다. 봄철에 가장 많이 발생하는 황사는 우리나라에 가장 크게 영향을 미치는 것이 만주지방에서 발생한 것인데, 굉장히 작은 입자들로 형성되어 있기 때문에 이동속도도 빠르고, 직접적으로 우리나라에 피해를 입히는 경우도 많은 것으로 파악된다. 또한 태풍의 크기와는 상관 없이 집중 호우를 동반하고 있는 기상현상에 대해서는 레이다 영상뿐만 아니라 기압도도 참고로 하여 분석하는 것이 더 필요할 것으로 생각된다. 인공위성 영상을 직접 분석하여 태풍이나 황사의 이동경로를 예측해 보고, 실제로 예측 결과가 맞는지 확인하는 작업을 수행함으로써, 정량적인 기상 예보 가능성을 추론해볼 수 있을 것이다. 자연 재해로 인한 피해를 줄이고 더 큰 인재로 확산되는 것을 방지하고자 하는 수단으로써 레이다 영상 분석을 동반하는 인공위성 영상 활용은 점차 그 가치가 높아질 것으로 예상된다.

• 대기
• /
• 제17권2호
• /
• pp.135-145
• /
• 2007

We developed a simple regression model for predicting the intesity change (central pressure) of major tropical cyclones (TCs) for 24 hours after landfall using 51 TC cases which landed over the Korean Peninsula for 1951-2004. Clusters 1 and 4 with a relatively strong intensity of TC after landfall classified by Choi and Kim (2007) are used to develop a statistical model for the prediction of TC intensity change. Predicting parameters (falling constants) in the regression models $(P_t=P_0+alnt)$ are 6.46 and 10.11 for clusters 1 and 4, respectively. It might be mentioned that there is some feasibility in employing a simple regression model developed in this study for TC intensity change after landfall for operational purpose of TC forecasting compared with RSMC-Tokyo best-track in both TC cases of Clusters 1 and 4 and Ewiniar (0603) case, but the room for improvement of model still remains for further study.

• 대기
• /
• 제18권4호
• /
• pp.525-532
• /
• 2008

This study has examined influences of tropical cyclone (TC) landfalls on the Gyoengsangbuk-do region, located in southeast of Korea, for the period 1978-2006. This region is known as one of major pass ways of landfalling TCs, and has many cultural properties including Bulguksa, Sukgulam, etc. Thus the influences caused by TCs (i.e., TC damages) may be larger than elsewhere in the nation. Here, TC influence is defined as the cases of strong instantaneous wind speed (${\geq}20ms^{-1}$) and heavy rainfall (${\geq}100mmday^{-1}$) at each station. This study analyzed long-term trends ofTC influences and the relationship with TC tracks are examined. As a result, it is found that large increase of the heavy rainfall cases along the coastal region. By contrast, there are marginal changes in the strong wind speed associated with TC landfalls. Further, it is also found that the cases of the heavy rainfall only are related with TCs passing through the Yellow Sea and the cases of both the strong wind and the heavy rainfall are related with TCs landing from southern Korea.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2021년도 추계학술대회
• /
• pp.338-340
• /
• 2021

최근 발생하는 자연 재난 중 홍수피해는 여름철에 집중되면서 태풍 장마로 인해 인명 피해나 재산피해로 이어진다. 이러한 피해를 줄이기 위해 많은 연구가 진행되고 있다. 본 논문에서는 이러한 돌발홍수 발생 시 최단 거리 알고리즘을 사용하여 경로를 검출하고 사용자에게 제공하는 시스템을 설계하고 구현한다. 제안하는 시스템은 QGIS를 사용하여 트랙과 포인터를 생성한 지형 데이터를 활용하여 경로를 검출한다. 또한 시나리오를 통하여 검출된 경로로 대피하는 과정에서 돌발홍수가 발생 시 다른 최단 경로를 검출하여 사용자에게 제공한다. 따라서 사용자는 제안하는 시스템을 통하여 향후 발생하는 재난 안전 사고 위험에 안전한 대피를 할 수 있을 것으로 사료한다.

• Journal of Astronomy and Space Sciences
• /
• 제34권4호
• /
• pp.257-270
• /
• 2017

Solar activity is known to be linked to changes in the Earth's weather and climate. Nonetheless, for other types of extreme weather, such as tropical cyclones (TCs), the available evidence is less conclusive. In this study the modulation of TC genesis over the western North Pacific by the solar activity is investigated, in comparison with a large-scale environmental parameter, i.e., El-$Ni{\tilde{n}}o$-Southern Oscillation (ENSO). For this purpose, we have obtained the best track data for TCs in the western North Pacific from 1977 to 2016, spanning from the solar cycle 21 to the solar cycle 24. We have confirmed that in the El-$Ni{\tilde{n}}o$ periods TCs tend to form in the southeast, reach its maximum strength in the southeast, and end its life as TSs in the northeast, compared with the La-$Ni{\tilde{n}}o$ periods. TCs occurring in the El-$Ni{\tilde{n}}o$ periods are found to last longer compared with the La-$Ni{\tilde{n}}o$ periods. Furthermore, TCs occurring in the El-$Ni{\tilde{n}}o$ periods have a lower central pressure at their maximum strength than those occurring in the La-$Ni{\tilde{n}}o$ periods. We have found that TCs occurring in the solar maximum periods resemble those in the El-$Ni{\tilde{n}}o$ periods in their properties. We have also found that TCs occurring in the solar descending periods somehow resemble those in the El-$Ni{\tilde{n}}o$ periods in their properties. To make sure that it is not due to the ENSO effect, we have excluded TCs both in the El-$Ni{\tilde{n}}o$ periods and in the La-$Ni{\tilde{n}}o$ periods from the data set and repeated the analysis. In addition to this test, we have also reiterated our analysis twice with TCs whose maximum sustained winds speed exceeds 17 m/s, instead of 33 m/s, as well as TCs designated as a typhoon, which ends up with the same conclusions.

• Smart Structures and Systems
• /
• 제24권2호
• /
• pp.243-256
• /
• 2019

Determination of the most meaningful structural modes and gaining insight into how these modes evolve are important issues for long-term structural health monitoring of the long-span bridges. To address this issue, modal parameters identified throughout the life of the bridge need to be compared and linked with each other, which is the process of mode tracking. The modal frequencies for a long-span bridge are typically closely-spaced, sensitive to the environment (e.g., temperature, wind, traffic, etc.), which makes the automated tracking of modal parameters a difficult process, often requiring human intervention. Machine learning methods are well-suited for uncovering complex underlying relationships between processes and thus have the potential to realize accurate and automated modal tracking. In this study, Gaussian mixture model (GMM), a popular unsupervised machine learning method, is employed to automatically determine and update baseline modal properties from the identified unlabeled modal parameters. On this foundation, a new mode tracking method is proposed for automated mode tracking for long-span bridges. Firstly, a numerical example for a three-degree-of-freedom system is employed to validate the feasibility of using GMM to automatically determine the baseline modal properties. Subsequently, the field monitoring data of a long-span bridge are utilized to illustrate the practical usage of GMM for automated determination of the baseline list. Finally, the continuously monitoring bridge acceleration data during strong typhoon events are employed to validate the reliability of proposed method in tracking the changing modal parameters. Results show that the proposed method can automatically track the modal parameters in disastrous scenarios and provide valuable references for condition assessment of the bridge structure.

• 대한토목학회논문집
• /
• 제39권6호
• /
• pp.691-702
• /
• 2019

홍수범람지도는 홍수에 대비하여 도시계획이나 댐 수위 조절 운영, 제방 등의 설계에 주요 지표로 사용되며 거주지역에 대한 홍수 발생 여부를 예보하거나 홍수 발생 시 신속하고 안전하게 대피하도록 하는 홍수 예·경보시스템 구축 등에도 중요한 역할을 한다. 국가하천과 같이 중요도 혹은 홍수 취약성이 높은 하천주변 지역의 경우, 고정밀도 LiDAR 기반 DEM 기반 정확도가 높은 홍수지도 작성에 2차원 혹은 3차원의 전문화된 범람지도 가시화 수치모형이 비용과 상관없이 활용될 수 있으나 지방하천 및 소하천은 예산상 한계 및 적합한 기술부족으로 여전히 시간소모적인 수작업이나 부정확하거나 비효율적인 기존 홍수지도작성 기법을 감수해왔다. 본 연구에서는, 실무에서 하천기본계획 수립 시 활용되는 HEC-RAS 기반 1차원 홍수위 모형 결과와 DEM을 기반으로 홍수지도작성의 복잡한 단계를 자동화시키고, 오픈소스인 QGIS와 연계할 수 있어 고비용의 ArcGIS에 기반하지 않는 OpenGIS 기반 홍수범람지도 생성 자동화 소프트웨어(Open Flood Mapper, OFM)를 개발하였다. OFM은 지난 2007년도 태풍 나리 내습 시 범람피해를 입은 제주도 한천 하류 침수흔적도, 첨두홍수위에 기반한 HEC-GeoRAS 및 수작업을 통해 제작한 홍수 범람지도와 비교하여 검증하였고, 빈도별 홍수범람지도를 추적하여 극한 홍수사상에서 범람의 특성을 시범적으로 구현하고 분석하였다.