• 한국농공학회지
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• 제42권1호
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• pp.66-72
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• 2000

A study was conducted to find distribution patterns of minisprinkler without a bridge for the desing of microirrigation systems. The experiments were executed in a plastic house to minimize the effect of the wind. Data were collected at four different operation pressures and at 3 different riser heights. Sprayed water were collected by aluminium cans with 65mm diameter and 100mm height placed at 0.3m grid spacing . A schematic distribution pattern with distance from a minisprinkler was suggested for the layout design of the minisprinkler. Distribution pattern of the minisprinkler was found irregular in space. Distributin performance characteristics of the minisprinkler such as effective radius. , effective area, mean application depth, absolute maximum application depth, effective maximum application depth and coefficient of variation were determined. It was indicated that there is a trend of decrease in variation coefficient adn better water distribution by the increase in operation pressures and riser heights.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(II)
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• pp.129-134
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• 2003

It is very important to pay careful attention to construction of bridge/earthwork transition zone for high-speed railway. The transition zone of the railway is the section which roadbed stiffness is suddenly varied. Differences in stiffness have dynamic effects and these increase the forces in the track and the extent of deformation. An abrupt change of stiffness across two adjacent track portions cause irregular settlement of roadbed, track irregularity, lack of girder bending moment and reduction of lateral resistance. Especially on high-speed railway, track irregularity of transition zone cause sincere effect to track stability and train safety. And so continuous maintenance is needed. To verify this effect and to improve transiton zone capacity, In situ test, track irregularity and train acceleration test were performed on high-speed railway bridge/earthwork Transiton Zone.

• 대한토목학회논문집
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• 제9권3호
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• pp.21-30
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• 1989

본 연구에서는 유한요소법과 실험적인 방법으로 이동하중용 받는 불규칙한 노면을 갖는 연속교의 동적거동을 연구하였다. 차량하중은 차축의 스프링효과를 포함하였으며 이로 인해 교량과 차량의 운동방정식은 결합된 미분방정식으로 표현되었고 이를 반복시산법으로 해결하였다. 실험적인 방법에서는 상사율을 고려하여 원형과 모형에서 동일한 동적거동이 나타나도록 모델을 제작하였고 이러한 교량 불규칙조도면, 진입부 단차면, 연속 단차면을 주어 실험하였다. 속도의 분포와 조도면의 양상 및 차량의 진동에 따른 교량의 동적거동을 이론 및 실험적인 방법으로 비교, 분석하였다.

• Composites Research
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• 제17권3호
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• pp.23-28
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• 2004

불균등 단면이나 임의의 경계조건을 가진 보나 탑 구조물의 고유진동수를 계산하는 방법은 김덕현에 의해 1960년 후반기에 개발 응용되고 1974년의 한 국제회의에서 발표되었다. 이 논문에는 이 방법을 탄성지지된 3경간연속 철근콘크리트 교량에 적용한 결과가 실려있다. 콘크리트 상판은 특별직교 이방성 판으로 취급되었다. 이 진동해석에 필요한 변위의 영향계수는 여러 방법으로 구할 수 있으나 이 논문에서는 유한차분법이 사용되었다. 기초의 탄성계수와, $D_{22}$, $D_{12}$, $D_{66}$ 강성의 고유진동수에 대한 영향이 철저하게 연구되었다.

• Structural Engineering and Mechanics
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• 제91권1호
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• pp.39-47
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• 2024

Bridge deterioration shows the change of bridge condition during its operation, and predicting bridge deterioration is important for implementing predictive protection and planning future maintenance. However, in practical application, the raw inspection data of bridges are not continuous, which has a greater impact on the accuracy of the prediction results. Therefore, two kinds of bridge deterioration models are established in this paper: one is based on the traditional regression theory, combined with the distribution fitting theory to preprocess the data, which solves the problem of irregular distribution and incomplete quantity of raw data. Secondly, based on the theory of Long Short-Term Memory (LSTM) Recurrent Neural Network (RNN), the network is trained using the raw inspection data, which can realize the prediction of the future deterioration of bridges through the historical data. And the inspection data of 60 prestressed concrete box girder bridges in Xiamen, China are used as an example for validation and comparative analysis, and the results show that both deterioration models can predict the deterioration of prestressed concrete box girder bridges. The regression model shows that the bridge deteriorates gradually, while the LSTM-RNN model shows that the bridge keeps great condition during the first 5 years and degrades rapidly from 5 years to 15 years. Based on the current inspection database, the LSTM-RNN model performs better than the regression model because it has smaller prediction error. With the continuous improvement of the database, the results of this study can be extended to other bridge types or other degradation factors can be introduced to improve the accuracy and usefulness of the deterioration model.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1126-1132
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• 2009

Bridge structures are designed to support ordinary loadings such as vehicles, wind, temperature and current as well as unexpected loadings like earthquakes and storm. Especially, the displacement of Flexible bridges like an suspension bridge under ordinary loading conditions is necessary to be monitored. In case of long span bridges, there are some difficulties in monitoring the displacement of center of the main span using traditional laser displacement sensors. In this study, the static and dynamic displacement responses due to vehicle loadings were measured by DGPS(differential global positioning system) technique. The displacement response data were compared with data obtained from traditional laser displacement sensors so that the static and dynamic behavior of the bridge under vehicle loadings was examined and the applicability of the displacement response measurement using DGPS technique was verified. The static and dynamic loading test for an self-anchored suspension bridge, So-rok Bridge, was performed using vehicles. The displacement response from DGPS technique and that from laser displacement sensors of the bridge monitoring system were compared. The amplitude of white noise from DGPS based measurement was about 7 mm and that of laser displacement sensor based measurement was about 3 mm. On the other hand, dynamic behavior of the center of main span from DGPS based measurement showed better agreement with influence line of the bridge than that from laser displacement sensors. In addition, there were some irregular and discontinuous variation of data due to the instability of GPS receivers or frequent appearance of GPS satellites. Post-processing via the reference station close to an observation post provided by NGII(National Geographic Information Institute) will be a counter-plan for these defects.

• 건축역사연구
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• 제23권1호
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• pp.7-19
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• 2014

This study considers the proper repair techniques by examining the most representative repair cases of the Korean arch bridges and proposes the constructional manual which can apply similar occasions. The cases are Seonamsa Seungseongyo and Songgwangsa Geukrockgyo where this researcher had taken part in the repair works. This Study proposes the maintenance construction manual about the performance degradation drew by performance degradation of the both Korean arch bridges in the maintenance process. First, arch bridge maintenance should be carried out in the dry season, when water is impermeable in the bottom surface of the bridge. Moreover, risk factors of the maintenance should be excluded to secure the water vally flow, the bypass and the temporary bridge. Second, prior to repair, it has to precede (1)3D shooting (2)formal examination (3)structure safety test (4)geological and lithic surveys (5)arch curvature establishment and makeshift frame settlement before transformation (6)relationship expert comments. Third, if the baduk and the foundation stones are inevitable to replace due to performance degradation on the foundation, it should use the high quality stones and secure greater stress by extending the standard range. The foundation on irregular rock needs to be flattened and underside on the replaced materials require Grengyijil to deliver the equal loads. Fourth, In the process of dismantling the stones of the arched bridge, it could make heavy weathering degree and not reuse the materials. Charge should converge the expert advices to choose the reuseable, the conservate and the alternative materials, and increase the reutilization of the raw materials by preservation and reinforcement treatments. Fifth, the side wall should be repaired by the rubble work technique which is not able to pile compost satiety, so it must use long depth of masonary stones for reinforcement. It is considered to reinforce the stone wall in shore as much as possible and protect the abutment and the side wall on the upstream for the arch bridge maintenance works.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.224-228
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• 2004

In these days, as it frequently happens that water level in the river exceeds the design floods due to irregular heavy rainfall, so it is required, first of an, to manage with railroad bridge safely. Because train control criterion under heavy rainfall is still not prepared and automatic flood monitoring system for railroad bridges is not used, worry over invisible economic loss due to train passage delay is in existence. Therefore, it is important to secure the safety and detect the risk like turnover or failure of railroad bridges through systematic disaster prevention system. And the transition from conventional monitoring method to real time monitoring method supported by sensors and communication system with high technology is rapidly needed. This research is on developing the real time flood monitoring system which prevents railroad disasters in advance by detecting continuously the water level of railroad bridge through CCD camera and water level gauge.

• 산업기술연구
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• 제16권
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• pp.139-145
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• 1996

Many of the bridge systems, including the girders and cross-beams, and concrete decks behave as the special othotropic plates. A method of calculating the natural frequency corresponding to the first mode of vibration of beam and tower structures with irregular cross-sections was developed and reported by D. H. Kim in 1974. Since 1989, The author has extended this method to Vibration analysis of two dimensional problems including composite laminates, and has reported at several conferenes. Frequently, the bridge floor panels are supported by girders and cross beams. Such panels as well as some of the building floor panels can be assumed as simple supported special orthotropic plates. In this paper, the result of application of simple method of vibration analysis developed by D. H. Kim, to the simply supported sandwich panels with point Mass/Masses is presented.

• 한국강구조학회 논문집
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• 제17권3호통권76호
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• pp.317-324
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• 2005

본 연구에서는 3경간연속 탄성지지된 복합슬래브교량을 특별직교이방성 판이론을 응용하여 해석하였다. 불균등단면이나 임의의 경계조건을 가진 보나 타워구조물의 고유진동수를 계산하는 방법을 탄성지지된 3경간 연속 복합슬래브교량에 적용하여 연구하였다. 슬래브 상판은 특별직교이방성 판으로 취급하였다. 진동해석에 필요한 변위의 영향계수는 여러 가지 방법으로 구할 수 있으나 본 논문에서는 유한차분법을 사용하였다. 또한 휨강성에 대한 영향과 기초의 탄성계수에 대한 영향에 대하여 연구하였다.