• Wind and Structures
• /
• 제25권2호
• /
• pp.195-214
• /
• 2017

Full-scale wind characteristics based on the field measurements is an essential element in structural wind engineering. Statistical analysis of the wind characteristics at Sutong Cable-stayed Bridge (SCB) site is conducted in this study with the recorded long-term wind data from structural health monitoring system (SHMS) between 2008 and 2015. Both the mean and turbulent wind characteristics and power spectra are comprehensively investigated and compared with those in the current codes of practice, such as the measured wind rose diagram, monthly maximum mean wind speed, turbulence intensity, integral length scale. Measurement results based on the monitoring data show that winds surrounding the SCB site are substantially influenced by the southeast monsoon in summer and strong northern wind in winter. The measured turbulence intensity is slightly higher than the recommended values in specifications, while the measured ratio of lateral to longitudinal turbulence intensity is slightly lower. An approximately linear relationship between the measured turbulence intensities and gust factors is obtained. The mean value of the turbulence integral length scale is smaller than that of typical typhoon events. In addition, it is found that the Kaimal spectrum is suitable to be adopted as the power spectrum for longitudinal wind component at the SCB site. This contribution would provide important wind characteristic references for the wind performance evaluation of SCB and other civil infrastructures in adjacent regions.

• 대한전자공학회논문지TC
• /
• 제45권8호
• /
• pp.106-113
• /
• 2008

본 논문에서는 ntop, ethereal, netperf, nettest 등 기존의 네트워크 모니터링 시스템의 취약점을 보안하고 동적인 firewall 기능을 가진 네트워크 트래픽 매니지먼트 시스템인 MAGI를 설계, 구현하고 이를 분석한다. MAGI 는 소프트웨어로 개발된 기존의 네트워크 모니터링 시스템과는 달리 소프트웨어와 하드웨어가 결합된 형태를 가진다. 소프트웨어 측면에서는 기존 모니터링 시스템과 차별화된 웹 유저 인터페이스(web user Interface) 시스템을 적용하여 트래픽 분석 및 방화벽 적용이 간편할 뿐만 아니라, 하드웨어의 상태를 모니터링 및 관리 할 수 있는 기능을 지닌다. 웹 유저 인터페이스는 PHP 와 MySQL 을 연동하여 데이터베이스(database)를 이용할 수 있어 데이터 분석이 간편한 장점을 지닌다. 하드웨어 파트인 어플라이언스(appliance)는 네트워크에 브릿지(bridge) 모드로 설치하여 모니터링 하는 시스템에 부하가 걸리지 않게 구현하였다. 또한, 어플라이언스 관리를 위하여 ncurses 기반의 인터페이스를 만들어 탑재함으로써 다양한 환경에 적용이 가능하다.

• Structural Monitoring and Maintenance
• /
• 제7권4호
• /
• pp.345-365
• /
• 2020

At present, many machine leaning and data mining methods are used for analyzing and predicting structural response characteristics. However, the platform that combines big data analysis methods with online and offline analysis modules has not been used in actual projects. This work is dedicated to developing a multifunctional Hadoop-Spark big data platform for bridges to monitor and evaluate the serviceability based on structural health monitoring system. It realizes rapid processing, analysis and storage of collected health monitoring data. The platform contains offline computing and online analysis modules, using Hadoop-Spark environment. Hadoop provides the overall framework and storage subsystem for big data platform, while Spark is used for online computing. Finally, the big data Hadoop-Spark platform computational performance is verified through several actual analysis tasks. Experiments show the Hadoop-Spark big data platform has good fault tolerance, scalability and online analysis performance. It can meet the daily analysis requirements of 5s/time for one bridge and 40s/time for 100 bridges.

• 한국구조물진단유지관리공학회 논문집
• /
• 제5권3호
• /
• pp.191-201
• /
• 2001

In spite of the increasing construction of segmental PSC box girder bridges, the techniques associated with real-time monitoring, construction control and safety assessment during construction have been less developed compared with the construction techniques. Thus, the development of an integrated system including real-time measurement and monitoring, control and safety assessment system during construction is necessary fur more safe and precise construction of the bridges. This study presents a prototype integrated monitoring system for preventing abnormal behavior and accidents under construction stages, that consist of behavior control system for precise construction, reliability-based safety assessment system, and structural analysis. Also, a prototype software system is developed on the basis of the proposed model. It is successfully applied to the Sea-Hae Grand Bridge built by FCM. The integrated system model and software system can be utilized for the safe and precise construction of segmental PSC bridges during construction.

• Smart Structures and Systems
• /
• 제3권3호
• /
• pp.373-384
• /
• 2007

For structural health monitoring (SHM) of civil infrastructures, displacement is a good descriptor of the structural behavior under all the potential disturbances. However, it is not easy to measure displacement of civil infrastructures, since the conventional sensors need a reference point, and inaccessibility to the reference point is sometimes caused by the geographic conditions, such as a highway or river under a bridge, which makes installation of measuring devices time-consuming and costly, if not impossible. To resolve this issue, a visionbased real-time displacement measurement system using digital image processing techniques is developed. The effectiveness of the proposed system was verified by comparing the load carrying capacities of a steel-plate girder bridge obtained from the conventional sensor and the present system. Further, to simultaneously measure multiple points, a synchronized vision-based system is developed using master/slave system with wireless data communication. For the purpose of verification, the measured displacement by a synchronized vision-based system was compared with the data measured by conventional contact-type sensors, linear variable differential transformers (LVDT) from a laboratory test.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 춘계 학술발표회
• /
• pp.1046-1050
• /
• 2010

During construction of a sea-crossing bridge grouting was used to fill densely the space between the bottom of caisson and the ground. This grout mixture was mixed with an anti-washout admixture after locating accurately the pre-cast caisson on three concrete landing pads. This method differs significantly from the costly conventional method, for bridge foundations offshore, where concrete is placed in situ after excavating inside of a temporary concrete coffering wall. To verify the grouting method in advance, the full-scale field tests were performed twice on land. After identifying the fluidity of the grout material to be filled, finding some possible problems with the main construction and revising the original design, the main construction has been continuing successfully with 20 caissons completed to date. The purpose of this paper is to introduce for the first time in Korea the grouting method including the automatic and the manual monitoring system based on the main construction of the caisson foundation.

• 한국방재학회:학술대회논문집
• /
• 한국방재학회 2008년도 정기총회 및 학술발표대회
• /
• pp.473-476
• /
• 2008

국내에는 2만개이상의 크고 작은 교량이 있으며, 매년 그 수가 늘어나고 있다. 현재는 이 중 일부 특수 교량에 상시 감시가 가능한 유지관리 모니터링 시스템을 구축하여 전문적으로 관리하고 있으나 앞으로 그 범위가 크게 확대 될 전망이다. 이런 교량 상시 유지관리 시스템의 기본 계측항목 중 경간 중앙부 처짐은 교량의 전체 안전 상태를 파악할 수 있는 중요한 계측항목이다. 본 연구는 지금까지 교량 상시 유지관리 시스템에 적용된 경간 중앙부 처짐에 대한 관리기준치 설정방법을 조사하고 간단한 실내 구조실험을 통하여 현재 적용 중인 교량 경간 중앙부 처짐에 대한 관리기준치의 여유도를 추정하여 보았다.

• Smart Structures and Systems
• /
• 제25권2호
• /
• pp.169-181
• /
• 2020

Sensor placement is a crucial aspect of bridge health monitoring (BHM) dedicated to accurately estimate and locate structural damages. In addressing this goal, a sensor placement framework based on the deflection influence line (DIL) analysis is here proposed, for the optimal design of damage detection-oriented BHM system. In order to improve damage detection accuracy, we explore the change of global stiffness matrix, damage coefficient matrix and DIL vector caused by structural damage, and thus develop a novel sensor placement framework based on the Fisher information matrix. Our approach seeks to determine the contribution of each sensing node to damage detection, and adopts a distance correction coefficient to eliminate the information redundancy among sensors. The proposed damage detection-oriented optimal sensor placement (OSP) method is verified by two examples: (1) a numerically simulated three-span continuous beam, and (2) the Pinghu bridge which has existing real damage conditions. These two examples verify the performance of the distance corrected damage sensitivity of influence line (DSIL) method in significantly higher contribution to damage detection and lower information redundancy, and demonstrate the proposed OSP framework can be potentially employed in BHM practices.

• 한국수자원학회논문집
• /
• 제36권6호
• /
• pp.893-899
• /
• 2003

본 연구에서는 하상이 단단한 지질구조로 이루어진 하상조건에서의 실제적인 세굴현상을 파악하기 위해 실시간 교량세굴 모니터링 시스템을 설치하여 홍수시의 세굴심을 측정하였다. 또한, 홍수 전$\cdot$후의 지반구조를 측정할 수 있는 GPR(Ground Penetrating Radar)탐사를 통하여 홍수로 인한 세굴가능성을 면밀히 파악하였다. 이와 같은 연구과정을 통해 지질구조에 따른 세굴심 산정공식의 적용성 여부를 판단하였고 하상특성과 흐름특성이 동시에 고려된 실제적인 세굴의 영향을 평가하였다.

• Steel and Composite Structures
• /
• 제46권6호
• /
• pp.731-744
• /
• 2023

Vehicle load information is an important role in operating and ensuring the structural health of cable-stayed bridges. In this regard, an efficient and economic method is proposed for vehicle load detection based on the observed cable tension and vehicle position using a graph neural network (GNN). Datasets are first generated using the practical advanced analysis program (PAAP), a robust program for modeling and considering both geometric and material nonlinearities of bridge structures subjected to vehicle load with low computational costs. With the superiority of GNN, the proposed model is demonstrated to precisely capture complex nonlinear correlations between the input features and vehicle load in the output. Four popular machine learning methods including artificial neural network (ANN), decision tree (DT), random forest (RF), and support vector machines (SVM) are refereed in a comparison. A case study of a cable-stayed bridge with the typical truck is considered to evaluate the model's performance. The results demonstrate that the GNN-based model provides high accuracy and efficiency in prediction with satisfactory correlation coefficients, efficient determination values, and very small errors; and is a novel approach for vehicle load detection with the input data of the existing monitoring system.