• Title, Summary, Keyword: cable-stayed bridge

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A Study on the Efficient Tension Estimation of Cables under Ambient Vibration using Minimized Measurement and Signal Processing System (최소화된 계측 및 신호 처리 시스템을 이용한 상시진동 케이블의 효율적인 장력 추정에 관한 연구)

  • Lee, Hyeong-Jin
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.11
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    • pp.594-603
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    • 2018
  • Recently, according to the development of measurement techniques, it has become possible to take complicated and time-consuming field measurements in a simple and convenient manner. In this background, this study estimated the tension of cables under ambient vibration using minimized measurement and signal processing. The VBDM using video-only by low-cost equipment was used as a minimized measurement. An estimation of the natural frequency using the mirror frequency concept was also proposed to solve the shortage of frequency band in this case. Furthermore, the FDD method was adopted for a natural frequency estimation in the ambient vibration related to field application. Experimental studies using a cable-stayed bridge model were carried out to examine the properties of the mirror frequency and the applicability of FDD with the proposed minimized system. The results showed that FDD for ambient vibration also works properly in an estimation of the natural frequency using the minimized system. In addition, the mirror frequency concept can allow a high natural frequency estimation even in a distorted signal by low-speed recording, which can overcome the limit of the minimized system. Overall, the proposed minimized system can be effective for the tension estimations of a cable under ambient vibration.

A Study on Buffeting Responses of a In-service Steel Cable-stayed Bridge Using Full-scale Measurements (실측 데이터를 이용한 공용중인 강사장교의 버페팅 응답 분석)

  • Lee, Deok Keun;Kong, Min Joon;You, Dong Woo
    • Journal of The Korean Society of Civil Engineers
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    • v.36 no.3
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    • pp.349-359
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    • 2016
  • In order to analytically evaluate buffeting responses, the analysis of wind characteristics such as turbulence intensity, turbulence length, gust, roughness coefficient, etc must be a priority. Static aerodynamic force coefficients, flutter coefficients, structural damping ratios, aerodynamic damping ratios and natural frequencies affect the analytical responses. The bridge interested in this paper has being been used for 32 years. As the time passes, current terrain conditions around the bridge are different markedly from the conditions it was built 32 years ago. Also, wind environments were considerably varied by the climate change. For this reason, it is necessary to evaluate the turbulence intensity, length, spectrum and roughness coefficient of the bridge site from full-scale measurements using the structural health monitoring system. The evaluation results indicate that wind characteristics of bridge site is analogous to that of open terrain although the bridge is located on the coastal area. To calculate buffeting responses, the analysis variables such as damping ratios, static aerodynamic force coefficients and natural frequency were evaluated from measured data. The analysis was performed with regard to 4 cases. The evaluated variables from measured data are applied to the first and second analysis cases. And the other analysis cases were performed based on Design Guidelines for Steel Cable Supported Bridges. The calculated responses of each analysis cases are compared with the buffeting response measured at less than 25m/s wind speed. It is verified that the responses by the numerical analysis applying the estimated variables based on full-scale measurements are well agreed with the measured actual buffeting responses under wind speed 25m/s. Also, the extreme wind speed corresponding to a recurrence interval 200 years is derived from Gumbel distribution. The derived wind speed for return period of 200 years is 45m/s. Therefore the buffeting responses at wind speed 45m/s is determined by the analysis applying the estimated variables.

Evaluation of Robust Performance of Fuzzy Supervisory Control Technique (퍼지관리제어기법의 강인성능평가)

  • Ok, Seung-Yong;Park, Kwan-Soon;Koh, Hyun-Moo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.9 no.5
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    • pp.41-52
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    • 2005
  • Using the variable control gain scheme on the basis of fuzzy-based decision-making process, Fuzzy supervisory control (FSC) technique exhibits better control performance than linear control technique with one static control gain. This paper demonstrates the effectiveness of the FSC technique by evaluating the robust performance of the FSC technique under the presence of uncertainties in the models and the excitations. Robust performance of the FSC system is compared with that of optimally designed LQG control system for the benchmark cable-stayed bridge presented by Dyke et al. Parameter studies on the robust performance evaluation are carried out by varying the stiffness of the bridge model as well as the magnitudes of several earthquakes with different frequency contents. From the comparative study of two control systems, FSC system shows the enhanced control performance against various magnitudes of several earthquakes while maintaining lower level of power required for controlling the bridge response. Especially, FSC system clearly guarantees the improved robust performance of the control system with stable reduction effects on the seismic responses and slight increases in total power and stroke for the control system, while LQG control system exhibits poor robust performance.

Safety Assessment of Corrosion-damaged Steel Structure using Imprecise Reliability (불확실 신뢰도 기법을 이용한 부식된 강구조물의 안전도평가)

  • Choi, Hyun Ho;Cho, Hyo Nam;Seo, Jong Won;Sun, Jong Wan
    • Journal of The Korean Society of Civil Engineers
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    • v.26 no.2A
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    • pp.293-300
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    • 2006
  • There is a high degree of uncertainty in measurements of the thickness or the loss of thickness of corroded elements. Generally the thickness of corroded elements varies from one location of the element to another depending on the degree of corrosion, which makes the safety assessment difficult. Therefore, a procedure for safety assessment of corrosion- damaged steel structures using an imprecise reliability is proposed in this paper. The proposed safety assessment procedure using the imprecise reliability was also applied to a cable-stayed bridge in Korea to demonstrate its effectiveness and applicability. Since there is a large variation in measurements of the thickness of corroded elements, the thickness of corroded elements was considered as the imprecise element. This variation was found to be directly related to the degree of corrosion. Therefore, the variation increases as the degree of corrosion increases. Based on the comparative observations between the conventional reliability and the imprecise reliability, it is suggested that the imprecise reliability analysis derived based on the subjective or statistical judgment of conditional independence could be successfully utilized for the risk or safety assessment of corrosion-damaged structures.

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2-Dimensional Section Model Experimental Study of 1200m Span Cable-Stayed Bridge (주경간 1200m급 사장교 2차원 단면모형실험)

  • Lee, Ho-Yeop;Chun, Nak-Hyun;Oh, Seung-Taek;Lee, Hak-Eun
    • 한국방재학회:학술대회논문집
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    • pp.76-76
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    • 2011
  • 현재까지 시공된 사장교 중, 주경간이 가장 긴 교량은 중국의 수통대교(1088m)이다. 이에 버금가는 사장교로 홍콩의 스톤커터교(1018m) 역시 주경간장이 1000m가 넘는다. 바야흐로 사장교 역시 주경간 1000m의 시대가 열린 것이다. 우리나라 역시 세계적 흐름에 맞추어 주경간 800m의 인천대교(세계 5위)를 시공한바 있다. 이와 같이 교량의 초장대화는, 교량 건설 분야에서 기술경쟁력의 지표가 될 뿐만 아니라 세계 건설 시장의 큰 흐름이라고 할 수 있다. 이에 본 연구는 세계적 추세에 발맞추어, 국내 각계의 건설 전문가들이 모여 만든 초장대 교량 사업단의 기술 혁신 사업의 일환으로 이루어졌다. 교량이 장대화 되면서 바람의 의한 영향이 중요해진다는 것은 주지의 사실이다. 특히 사장교와 현수교 같은 특수 교량의 경우, 정적 및 동적 내풍 성능이 반드시 고려되어야만 한다. 본 연구에서는 주경간 1200m의 사장교를 가정하고, 이 사장교의 내풍 단면을 개발, 그 단면에 대한 정적 및 동적 내풍 성능을 평가하고자 하였다. 정적 내풍 성능으로는 단면의 형상에 따른 풍하중을 파악하고자 했으며, 동적 내풍 성능으로는 풍속에 따른 교량의 연직방향 변위 및 플러터 속도를 파악하고자 하였다. 이 실험은 추후에 3차원 전교모형실험의 기본 데이터로 활용하였다. 본 실험을 통해 개발된 단면의 등류 및 난류 상태에서의 영각별 정적 공기력계수를 계산해내었고, 설계풍속이 54.7m/s일때 한계풍속 65.64m/s(거마대교 기준)하에서의 중앙 경간의 풍속별 평균 변위를 측정하였으며, 이를 토대로 이 교량의 영각별 플러터 속도를 계산해 내었다.

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Safety Evalution of on the cable of Extra dosed bridges by fire (화재에 대한 Extra-dosed교 케이블의 안전성 평가)

  • Rhu, Bong-Jo;Song, Young-Sun;Park, Weon-Tae
    • Journal of Korean Society of Hazard Mitigation
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    • v.8 no.5
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    • pp.23-33
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    • 2008
  • Extra dosed bridge among the Cabled-stayed bridges have been increasingly built in korea in recently. But such bridges were often damaged by fire due to car collison. In this study Extra dosed bridges among the cabled-supported bridges are selected to analysis model frequently to be designed and/or constructed in recent and furture in this study. COSMOS FloWorks 2007 software are used for Heat Transfer Analysis and Thermal Stress Analysis. The safety of wire, HDPE pipe and stainless steel pipe are investigated. In the case of the constant of the temperature of the heat source, the significant three variables for the analysis are selected for study : (1) the distance between the fire-proof bulk head and the heat source, (2) wind velocity, (3) the height of the end of Stainless steel pipe.

An Instantaneous Integer Ambiguity Resolution for GPS Real-Time Structure Monitoring (GPS 실시간 구조물 모니터링을 위한 반송파 관측데이터 순간미지정수 결정)

  • Lee, Hungkyu
    • Journal of The Korean Society of Civil Engineers
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    • v.34 no.1
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    • pp.341-353
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    • 2014
  • In order to deliver a centimeter-level kinematic positioning solution with GPS carrier-phase measurements, it is prerequisite to use correctly resolved integer ambiguities. Based on the mathematical modeling of GPS network with application of its geometrical constraints, this research has investigated an instantaneous ambiguity resolution procedure for the so-called 'integer constrained least-squares' technique which can be effectively implemented in real-time structure monitoring. In this process, algorithms of quality control for the float solutions and hypothesis tests using the constrained baseline for the ambiguity validation are included to enhance reliability of the solutions. The proposed procedure has been implemented by MATLAB, the language of technical computing, and processed field trial data obtained at a cable-stayed bridge to access its real-world applicability. The results are summarized in terms of ambiguity successful rates, impact of the stochastical models, and computation time to demonstrate performance of the instantaneous ambiguity resolution proposed.

The Unified Wireless Control System for the Vibration Control of Bridge (교량의 진동제어를 위한 통합 무선제어 시스템)

  • Heo, Gwang Hee;Kim, Chung Gil;Oh, Ju Won
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.2
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    • pp.65-74
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    • 2012
  • This paper aimed at the development of a unified wireless control system in order to control various forms of vibration of bridges. This unified wireless control system unified all different systems each of which functioned for difference purpose such as measurement, analysis, judgement, and control of data acquired from the movement of structure. It was designed to control structures with feedback which was returned according to each different situation after analyzing various signals measured about the structure. In this system, every information in each step from measurement to control was wirelessly transmitted to its central system so that a manager was able to effectively monitor the whole process. Just for the case when any system control need to intervene occurred, a graph user interface was designed for better access. In order to evaluate its basic performance, an experiment was carried out to see how signal input and output were done by comparing its results with those of a wired system. On the basis of the experiment, a vibration control experiment was performed on a model of cable-stayed bridge to see if the unified wireless control system worked well in realtime. This was carried out under four conditions, and the graph and quantitative result under each condition were compared each other. All experiments proved that the unified wireless control system functioned as well as the wired one in terms of its basic performance and vibration control.

Application of Tuned Mass Damper to Suppress Man-Induced Vibrations of Cable Stayed Foot-bridge (사장교형식 보도교의 보행진동제어를 위한 TMD 적용)

  • Kim, Yun-Seok;Lee, Seung-Woo;Kim, Jae-Min;Chang, Seong-Kyu
    • 한국방재학회:학술대회논문집
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    • pp.74-74
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    • 2011
  • 본 연구에서는 중앙경간 54m, 교폭 4m의 사장교형식의 보도교로 측경간은 계단으로 이루어진 1경간 케이블교량을 대상으로 보행하중에 의한 수직진동을 제어하기 위해 제진장치(TMD)를 적용하기로 하고 실물 TMD의 설계 및 제작 그리고 설치 및 제어성능실험을 수행하였다. 우선 사장교형식의 교량. 그리고 1경간 교량이라는 점에서 상대적으로 감쇠율이 낮을 것으로 예측되었고 또한 54m의 경간장이 보행자가 가진 주파수에 근접한 고유진동수를 나타낼 것으로 사료되어 Eurocode 2 part 2(EC5-2)의 규준에 따라 1인 및 다수 보행하중에 의한 보도교의 발생가속도를 산출하였다. 이 경우 최대가속도는 다수의 보행자가 연속적으로 진행할 때 발생하였으며, 수직방향의 가속도가 사용성기준을 초과하는 것으로 나타났다. 또한 구조해석프로그램에 의한 고유치 해석결과, 보행하중의 주파수대역내에 진동모드가 존재하는 것으로 나타났다. 따라서 본 교량의 설계단계에 있어서 보행진동을 제어하기 위하여 유지관리가 용이한 수동형의 동조질량감쇠장치(Tuned Mass Damper)를 적용하기로 하였으며 TMD의 설계에서는 TMD의 제어목표를 만족시킬 수 있는 TMD의 가동질량(moving mass)을 우선적으로 결정하였고, 이로부터 Den Hartog의 제안식에 따라 TMD의 고유진동수비, 유효감쇠비를 산정하였다. 산정된 변수들을 이용하여 설계된 TMD는 현장설치 및 튜닝의 편의성을 고려하여 수평 외팔보형식으로 설계, 제작되었으며 제작된 TMD의 경우 회전축에 대해 질량, 스프링, 댐퍼의 중심거리를 조정함으로써 TMD의 진동수, 강성, 감쇠력을 상대적으로 매우 용이하게 조절할 수 있으며, 조정범위 또한 광범위하여 일반 TMD에 비해 현장설치시 대상구조물에 동조시키기가 용이하며, 작동시 마찰감쇠가 거의 없다는 장점이 있다. 현장설치전에 제작된 TMD를 대상으로 자유진동 시험을 통하여 질량의 중심거리, 스프링 크기 그리고 댐퍼의 설치유무를 각각 변화시키며 TMD의 자유진동 데이터를 취득하였다. 각각의 시험에서 얻어진 데이터로부터 스펙트럼해석을 통하여 고유진동수를 구하였고, 자유진동 파형으로 부터 감쇠비를 구하였다. TMD는 일반적으로 제어모드의 변형형상이 가장 큰 곳에 설치되었을 때 최대의 제진효과를 발휘할 수 있다. 그러나 현장여건상 설치가 불가능하거나 미관을 해치는 경우에는 가능한 범위 내에서 TMD 제어효율이 가장 크게 발휘할 수 있는 곳을 선택하여야 한다. 본 보도교의 경우, 중앙경간 중심부에서 가장 큰 모드변형형상을 나타내지만, 보도교의 상판 연결부 등에 따른 TMD 시공문제로 인하여 TMD 설치위치는 교량 중앙에서 양 방향으로 1.25m 떨어진 곳에 대칭으로 총 2기를 설치하기로 하였다. 일반적으로 TMD의 모든 설계변수는 구조물의 설계단계에서 수행된 구조해석결과에 근거하여 설정하므로 완공된 구조물, 즉 실제보도교의 동적특성을 계측하여 정확하게 진동수를 튜닝하여야 한다. 구조해석에 의한 보도교의 수직방향(TMD 작동방향) 고유진동수는 1.5225 Hz이며, 감쇠비는 규준에 의하여 0.6 %로 가정하였다. 그러나 이 값들은 구조해석모델 및 재료적 특성과 시공상의 오차에 의하여 실제와 다를 수 있으므로 현장계측에 의한 확인이 요구된다. 또한 TMD의 제진효율이 설계시의 목표대로 확보되었는지도 확인해야 하므로 현장튜닝 및 성능시험을 실시하였다. 보도교의 가진은 사전에 실시한 상시 미진동계측결과를 토대로 2Hz를 목표로 하여 인력가진실험을 수행하였고, 탁월진동 주파수는 1.9896Hz로 나타나 구조해석결과와 오차가 있음을 알 수 있다. 가진실험결과를 토대로 TMD의 진동수를 최적진동수비로 튜닝하고 인력가진 실험을 다시 실시하여 TMD의 진동제어성능을 검토하였다. TMD 튜닝 전, 후의 보도교 감쇠비를 비교한 결과, TMD를 설치함으로써 약 4.218%의 감쇠비 증가가 있음을 알 수 있다.

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