• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.77.1-77.1
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• 2010

본 연구에서는 가속도기반 무선센서노드와 MEMS 가속도계 센서를 이용하여 철도교량의 구조건전성모니터링 기법들의 성능을 검토하였다. 이를 위해 다음과 같은 세 단계의 연구가 수행되었다. 첫째, 저가형 가속도기반 무선센서노드를 설계하였다. 둘째, 철도교량의 구조건전성모니터링을 위한 진동특성 및 건전성평가기법을 선정하였다. 마지막으로, 모형 강판형교에 대한 진동실험을 통해 개발된 가속도기반 무선센서노드의 성능을 평가하고 일련의 손상 시나리오를 대상으로 건전성평가 기법의 성능을 검토하였다. 시간영역 기법인 AR 모델과 주파수영역 기법인 파워스펙트럼 상관계수가 강판형교 구조손상 모니터링에 높은 정확도를 보였다.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.690-695
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• 2002

Two plate girders bridge has an advantage for execution of works and quality control because of its simplicity of super-structure caused by decreasing in amount of members and also is distinguished as aesthetic bridge type. Recently this has been adopted for structure of highway as well railway and introduced into domestic. In order to plan or design two plate girders bridge more rationably, it is necessary to comprehend its structural behavior as well as to consider the critical resign factors. Thus, in this study the formulation of optimum design for two plate girders bridge is proposed and the critical resign variables ani restraints are considered and founded by caring out optimum design. The objective function of optimization is formulated as a minimum cost design problem. And the thickness and length of I-shaped section are decided as resign variables. The design constraints are formulated based on Design Criteria for Railroad(Bridges). By comparing the optimum results with those of the conventional resign, the effectiveness of proposed optimum design formulation is investigated. From the results, the way to do optimum design of two plate girders bridge is suggested.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.6
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• pp.317-327
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• 2018

The perception of earthquake in Korea has changed due to the earthquake that occurred in Gyeongju and Pohang, and the earthquake has become an important factor in infrastructure management. Damage to infrastructures in the event of an earthquake is extensive. In particular, damage to infrastructures that perform public function used to spread to the whole area. From the point of view of earthquake disaster prevention, it is very important for the public to define what infrastructures are important management targets and to prepare a countermeasure. In this study, we propose a method to evaluate the importance of infrastructure to effectively manage infrastructures for earthquakes. For this purpose, important factors for the railway bridges, power generation and electric power facilities, and apartment complexes are suggested. AHP analysis is conducted to suggest priorities. In addition, the evaluation criteria for infrastructure importance are presented.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.4
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• pp.305-312
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• 2007

Among many types of light rail transits (LRT), the rubber-tired automated guide-way transit (AGT) is prevalent in many countries due to its advantages such as good acceleration/deceleration performance, high climb capacity, and reduction of noise and vibration. However, AGT is generally powered by high-voltage electric power feeding system and it may cause electromagnetic interference (EMI) to measurement sensors. The fiber optic sensor system is free from EMI and has been successfully applied in many applications of civil engineering. Especially, fiber Bragg grating (FBG) sensors are the most widely used because of their excellent multiplexing capabilities. This paper investigates a prestressed concrete girder bridge in the Korean AGT test track using FBG based sensors to monitor the dynamic response at various vehicle speeds. The serviceability requirements provided in the specification are also compared against the measured results. The results show that the measured data from FBG based sensors are free from EMI though electric sensors are not, especially in the case of electric strain gauge. It is expected that the FBG sensing system can be effectively applied to the LRT railway bridges that suffered from EMI.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.751-760
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• 2021

Most bridges in Korea are over 20 years old, and many problems linked to their deterioration are being reported. The current practice for bridge inspection mainly depends on expert evaluation, which can be subjective. Recent studies have introduced data-driven methods using building information modeling, which can be more efficient and objective, but these methods require manual procedures that consume time and money. To overcome this, this study developed an image-based automaticbridge component classification network to reduce the time and cost required for converting the visual information of bridges to a digital model. The proposed method comprises two convolutional neural networks. The first network estimates the type of the bridge based on the superstructure, and the second network classifies the bridge components. In avalidation test, the proposed system automatically classified the components of 461 bridge images with 96.6 % of accuracy. The proposed approach is expected to contribute toward current bridge maintenance practice.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.821-831
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• 2006

There are 5 railway bridges in a Seoul metro network; Jamsil, Dangsan(line 2), Dongho(line 3), Dongjak(line 4) and Chungdam(line 7). Because there are strong wind and vibration in the bridges, uplift of a contact wire caused by pantographs in the bridge section is higher than in a normal section. If the uplift at the support point exceed 10 cm, an interference between pantographs and catenary system happens. Estimated maximum uplift is obtained by applying safety factor 2 to the simulation results. The application of the safety factor is needed for taking into account of the effect of the wind, etc. Previously, we can not check whether or not the safety factor is proper. Recently, we can measure the uplift during the train operation, as a telemetry system which can measure dynamic behavior of the contact wire has been developed. The aim of this research is to review how proper the safety factor related to the uplift is, based on the measurement. We performed simulations and experiments for the uplift at the Jamsil railway bridge. The simulations were performed for the every kind of the train passing the Jamsil bridge. In order to compare the analysis results with the measurement results, we measured the uplifts at the support when the trains passed the measuring point. Finally, we proposed adequate safety factor with the uplift for the bridge section.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.1
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• pp.39-48
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• 2023

Because a railway bridge is designed over a long period of time and covers a large site, it involves various environmental factors and uncertainties. For this reason, design changes often occur, even if the design was thoroughly reviewed in the initial design stage. In particular, design changes of large-scale facilities, such as railway bridges, consume significant time and cost, and it is extremely inefficient to repeat all the procedures each time. In this study, a technique that can improve the efficiency of learning after design change was developed by utilizing the learning result before design change through transfer learning among deep-learning algorithms. For analysis, scenarios were created, and a database was built using a previously developed railway bridge deep-learning-based prediction system. The proposed method results in similar accuracy when learning only 1000 data points in the new domain compared with the 8000 data points used for learning in the old domain before the design change. Moreover, it was confirmed that it has a faster convergence speed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.1-9
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• 2016

Railroad bridges account for 25% of the entire high-speed rail network. Railway bridges are subject to gradual structural degradation or fatigue accumulation due to consistent and repeating excitation by fast moving trains. Wireless sensing technology has opened up a new avenue for bridge health monitoring owing to its low-cost, high fidelity, and multiple sensing capability. On the other hand, measuring the transient response during train passage is quite challenging that the current wireless sensor system cannot be applied due to the intrinsic time delay of the sensor network. Therefore, this paper presents a framework for monitoring such transient responses with wireless sensing systems using 1) real-time excessive vibration monitoring through ultra-low-power MEMS accelerometers, and 2) post-event time synchronization scheme. The ultra-low power accelerometer continuously monitors the vibration and trigger network when excessive vibrations are detected. The entire network of wireless smart sensors starts sensing through triggering and the post-event time synchronization is conducted to compensate for the time error on the measured responses. The results of this study highlight the potential of detecting the impact load and triggering the entire network, as well as the effectiveness of the post-event time synchronized scheme for compensating for the time error. A numerical and experimental study was carried out to validate the proposed sensing hardware and time synchronization method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1A
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• pp.31-43
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• 2009

In this study, the numerical method is presented, which can consider the various train types and can solve the equations of motion for a vehicle-bridge interaction analysis by non-iteration procedure through formulating the coupled equations of motion. The coupled equations of motion for the vehicle-bridge interaction are solved by the Newmark ${\beta}$ of a direct integration method, and by composing the effective stiffness matrix and the effective force vector according to a analysis step, those can be solved with the same manner of the solving procedure of equilibrium equations in static analysis. Also, the effective stiffness matrix is reconstructed by the Skyline method for increasing the analysis effectiveness. The Cholesky's matrix decomposition scheme is applied to the analysis procedure for minimizing the numerical errors that can be generated in directly calculating the inverse matrix. The equations of motion for the conventional trains are derived, and the numerical models of the conventional trains are idealized by a set of linear springs and dashpots with 16 degrees of freedom. The bridge models are simplified by the 3 dimensional space frame element which is based on the Euler-Bernoulli theory. The rail irregularities of vertical and lateral directions are generated by the PSD functions of the Federal Railroad Administration (FRA). The results of the vehicle-bridge interaction analysis are verified by the experimental results for the railway plate girder bridges of a span length with 12 m, 18 m, and the experimental and analytical data are applied to the low pass filtering scheme, and the basis frequency of the filtering is a 2 times of the 1st fundamental frequency of a bridge bending.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.241-247
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• 2017

Railway bridges with continuously welded rail have a limitation of span length due to track-bridge interaction. In order to overcome this, a sliding slab track system has been developed that comprises with a low-frictional sliding layer between the bridge deck and the track slab to isolate the longitudinal behavior between the bridge and the track. In this study, a real scale track system is prepared to experimentally evaluate the longitudinal frictional behavior. Applied loading rates were 0.2, 1.0, 5.0 and 10mm/min; vertical mass on the track are track slab only, 5,000 and 10,000kg added mass, respectively. Test results showed that the resulting frictional coefficients varied from 0.22 to 0.33. In addition, 10,000 cycle loadings were applied to simulate repetitive sliding to represent 30 years of service life. The frictional coefficient increase was measured and found to be 7% of that of the initial loading stage, which means that the sliding layer is adequate to provide low-frictional behavior for the sliding slab track system. Effects of changes of the frictional coefficient of the sliding layer were analyzed by rail-structure interaction analysis.