• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.208-208
• /
• 2009

최근 광섬유 센서기술의 수요는 전 산업분야에 걸쳐 높아지고 있으며, 이에 비례하여 기업 간, 국가 간 경쟁이 첨예화되고 있다. 또한 소형화, 경량화, 고성능화 센서에 대한 요구도 높아지고 있어 종래의 각종 센서들의 형태와 개선을 위한 연구개발이 매우 활발하게 전개되고 있으므로 이를 대체할 수 있는 광섬유 센서의 수요가 급격히 늘어날 전망이다. 기존 침입자 감지 시스템은 태풍, 낙뢰, 폭설, 폭우 등의 기상변화나 지반 흔들림, 통행차량 진동 및 전자기 간섭 등에 영향을 받아 오작동, 오경보가 빈번히 발생된다. 이러한 문제의 해결책으로 광섬유 센서 케이블을 이용한 시스템이 대안으로 부각되고 있다. 현재 국내에서 군부대, 공항을 중심으로 펜스와 휴전선 철책에 힘입자 감지를 위하여 도입되고 있다. 광섬유 센서 케이블을 사용하는 광망경비시스템은 광섬유 센서 케이블을 그물망 형태(광망)로 만들어 경계 지역에 설치된다. 광망경비시스템의 원리는 광섬유에 광펄스를 입사시켜 순환시키는데 침입자가 광망을 절단하거나 외력을 가할 경우 발생되는 레일리 산란에 기인하는 후방산란과 접속점과 파단점에서 생기는 반사광을 OTDR(Optical Time Domain Reflectometer)로 검출하여 침입상황 및 침입위치를 탐지한다. 그러나 이러한 침입자 감지를 위한 광망경비시스템의 핵심부품인 광섬유 센서 케이블은 기존에 전량 해외수입에 의존하고 있는 실정이며, 지금까지 국내에서 생산하기 위한 제작 기술과 노하우가 초보단계에 머물러 있다. 이러한 광섬유 센서 케이블 제작에 있어서 중요한 부분이 패키징 기술이라 할 수 있다. 이는 광섬유 센서를 일반적인 피복 구조로 패키징하게 되면, 센서 고유의 특성이 패키징 과정과 운반과정, 포설과정에서 변하게 되고 센서로써의 신뢰성이 크게 저하된다. 본 연구에서는 힘입자 감지용 광섬유 센서 케이블의 설계와 제작을 위한 제조공법을 확립하고, 이를 이용해 제작된 광섬유 센서 케이블의 신뢰성 특성을 평가하였다. 설계 제작된 광섬유 센서 케이블의 구조는 멀티모드광섬유(MMF) 에 0.9 mm Tight buffer를 코팅하고, 광심선 주위에 아라미드 얀을 삽입시킨 후 고문자 수지를 적용하여 외부 피복 (jacket)을 하였다. 제작된 광섬유 센서 케이블의 외경 측정결과 기준치 ($2.95\;{\pm}\;0.03$ mm)를 모두 만족하였고, 850 nm 파장에서의 광 손실 측정 결과 4.0 dB/km 이하였다. 또한 주요 항목의 신뢰성 특성 시험결과, 인장강도는 8~10 kg의 인장력을 갖으며 온도순환시험 ($-30^{\circ}C\;{\sim}\;+75^{\circ}C$)에서의 광 손실은 0.6 dB 이하로 나타나 침입자 감지용 광섬유 센서 케이블로 적합함을 확인할 수 있었다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.4
• /
• pp.127-134
• /
• 2005

Design and construction of long-span bridge are recently increasing by development of computer technology. Specially, cable stayed bridge and suspension bridge having cable component are representative of long-span bridge may do. Therefore, this paper a present a methodology for cable tension force monitoring in cable-stayed bridge under construction using acceleration data acquired by the vibration method. To improve accuracy construction, all stay cables are measured, according to 4-step construction stage and change of temperature.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.3
• /
• pp.129-138
• /
• 2005

This paper presents a methodology for the determination of optimal managing criteria for cable tension force in cable-stayed bridges using acceleration data acquired by monitoring system. There are many long span bridges installed with monitoring system in Korea. The monitoring systems are installed to diagnose abnormal behavior or damages in bridges and to warn these to bridge management agency. In cable-stayed bridges, the cable tension force could be an important indicator of abnormal behavior because of the geometric configuration of the cable-stayed bridge. If the management value of cable tension force is set too high or too low, then the monitoring system could not warn properly for the abnormal behavior of a bridge. Generally, the management value is set by empirical or engineering judgment, but in this paper, a new methodology for the determination of managing criteria for cable tension force is proposed based on the probability distribution model for tension force and reliability analysis. The proposed methodology is applied to a real concrete cable-stayed bridge in order to investigate its applicability.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.1A
• /
• pp.51-58
• /
• 2008

A cable element happens to vibration easily rather than other elements because a cable element has few rotational stiffness. Dynamic motion of stay cable is distinguished from vibration by wind and/or rain and excitation by support movement. Mostly a stay cable is vibrated by wind and/or rain except that when natural periods coincide between stiffening girder and stay cable. It happens to deterioration of serviceability and durability by vortex shedding, rainy-wind induced vibration, and galloping. Additional damping generated by installation of cable damper is well known good scheme against above phenomena. Researchers have lack of effort to develop the recommendations even if cable stayed bridges are designed and constructed in Korea. Therefore, development of the domestic recommendations should be achieved as soon as possible. This study suggests the consistent and systematic recommendations on vibration controlling design of stay cable by installation of damper. It gives readers two important methodologies that one evaluates required damping ratio, the other determines installing point considering efficiency.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.6
• /
• pp.60-71
• /
• 2014

Cable-stayed bridge, which is one of the representative long-spanned bridge, needs prompt maintenances when a stay cable is damaged because it may cause structural failure of the entire bridge. Many researches are being conducted to develop abnormal behavior detection algorithms for the purpose of shortening the reaction time after the occurrence of structural damage. To improve the accuracy of the damage detection algorithm, ample observation data from various kinds of damage responses is needed. However, it is difficult to measure an abnormal response by damaging an existing bridge, numerical simulation can be an effective alternative. In most previous studies, which simulate the damage responses of a cable-stayed bridge, the damages has been considered as a load variation without regard to its stiffness variation. The analyses of using these simplification could not calculate exact responses of damaged structure, though it may reserve a sufficient accuracy for the purpose of bridge design. This study suggests Gradual Bilinear Method (GBM) which simulate the damage responses of cable-stayed bridge considering the stiffness and mass variation, and develops an analysis program. The developed program is verified from the responses of a simple model. The responses of a existing cable-stayed bridge model are analyzed with respect to the fracture delay time and damage ratio. The results of this study can be used to develop and verify the highly accurate abnormal behavior detection algorithm for safety management of architecture/large structures.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.6
• /
• pp.172-181
• /
• 2023

In this study, real-time damage evaluation of cable-stayed bridges was conducted for cable damage. ICP type acceleration sensors were used for real-time damage assessment of cable-stayed bridges, and Kinetic Energy Optimization Techniques (KEOT) were used to select the optimal conditions for the location and quantity of the sensors. When a structure vibrates by an external force, KEOT measures the value of the maximum deformation energy to determine the optimal measurement position and the quantity of sensors. The damage conditions in this study were limited to cable breakage, and cable damage was caused by dividing the cable-stayed bridge into four sections. Through FE structural analysis, a virtual model similar to the actual model was created in the real-time damage evaluation method of cable. After applying random oscillation waves to the generated virtual model and model structure, cable damage to the model structure was caused. The two data were compared by defining the response output from the virtual model as a corruption-free response and the response measured from the real model as a corruption-free data. The degree of damage was evaluated by applying the data of the damaged cable-stayed bridge to the Improved Mahalanobis Distance (IMD) theory from the data of the intact cable-stayed bridge. As a result of evaluating damage with IMD theory, it was identified as a useful damage evaluation technology that can properly find damage by section in real time and apply it to real-time monitoring.

• Proceedings of the KIEE Conference
• /
• 2002.11b
• /
• pp.326-328
• /
• 2002

본 논문에서는 케이블 내전압 시험 및 부분 방전 측정 시험에 사용될 수 있는 전구 차단 장치의 차단 기준에 큰 영향을 미치는 케이블 부분방전 센서의 특성에 관한 연구를 수행하였다. 특히, 부분방전 발생시 부분방전 발생 위치를 보다 정확하게 판별할 수 있는 센서의 종류 및 구조를 주파수 특성과 시간 특성을 함께 측정한 결과를 보고한다.

• Proceedings of the KIEE Conference
• /
• 1997.07e
• /
• pp.1651-1653
• /
• 1997

본 보고는 육지로부터 1.1km 떨어진 하섬에 전력, 통신, 제어케이블을 각각 포설공사한 결과이다. 먼저 포설공사전에 Route의 유속과 수심, 해저면등의 조건을 각각 측정하였다. 하섬의 부하를 계산하고 케이블의 전압 및 허용전류등을 계산한후에 해저 직매에 적합한 구조 및 수밀특성을 향상시키는 설계를 하였다. 또한, 시이즈의 표면은 포설시에 손상을 줄이기 위하여 Smooth형으로 제조하였다. 포설은 전력, 제어, 통신케이블을 동시에 직매식으로 최단시간내에 수행하는 공사를 하였으며, 케이블의 진단은 직류전압법에 의한 전류특성으로 평가하였다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.6
• /
• pp.147-154
• /
• 2014

The cable damages of the bridge structures induce very important impact on the structural safety, which implies the close monitoring of the cable damage is required to secure sustained safety of the bridges. Most usual available maintenance techniques are based on the monitoring the change of the natural frequency of the structures by damages. However, existing method are based on vibration method to calculate lateral vibration and system identification can calculate the axial stiffness using sensitivity equation by trial error method. But the frequency study by the longitudinal movement need because of the sag effect in system identification. This study proposes a new method to investigate the damage magnitudes and status. The method improves the accuracies in the magnitudes and status of damages by adopting the natural frequency of longitudinal movement. The study results have been validated by comparing them with the approximate solution of FEM. Thus, the relationship of cable damage and frequency appear with relation that the severe damage has the little frequency. If we know the real frequency we can estimate the cable damage severity using this relationship. This method can be possible the efficient management of the cable damage.

• Journal of Korean Society of Steel Construction
• /
• v.22 no.4
• /
• pp.345-354
• /
• 2010

This paper presents an experimental investigation of the structural performance of a large-span girder bridge with an under-tension system. Typical long-span structures with beam and girder members have greater structural member depths and sizes to carry the moment and deflection. An under-tension system can be an effective structural system, as it allows the cables to resist some portions of the vertical loadings and deflections. To evaluate the serviceability and ultimate strength of the under-tension system, two $10m{\times}2.4m$ experimental under-tension systems were built and tested. One was developed with an H-beam section, and the other was made with a PF500 section that had the advantages of fast construction and lower construction cost. In the test, the maximum deflections at the mid-point of both beams were effectively reduced using under-tension systems. Also, the increased tension forces in the cable reduced the deflections. The PF500 members, which had a new shape and were developed using the module systems, performed better than the typical H-beam sections in terms of the deflections and ultimate strength.