• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.545-548
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• 1999

The purpose of this study is application of strengthening technique of R/C concrete bridge by standardization of repair and rehabilitation. For that, experiment to bridge is necessary, and through the experiment, this study can identify the efficiency o applied method and analysis of design parameters with can't get in the laboratory experiment. This study will prove the structural behavior of R/C type girder bridge which is deteriorated but repaired and rehabilitation from standardized strengthening method with fiber plastic.

• Earthquakes and Structures
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• 제15권3호
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• pp.275-283
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• 2018

Seismic strengthening is essential for existing bridge piers which are deficient to resist the earthquake. The concrete and CFRP jackets with a bottom-anchoring method are used to strengthen railway bridge piers with low reinforcement ratio. Quasi-static tests of scaled down model piers are performed to evaluate the seismic performance of the original and strengthened bridge pier. The fracture characteristics indicate that the vulnerable position of the railway bridge pier with low reinforcement ratio during earthquake is the pier-footing region and shows flexural failure mode. The force-displacement relationships show that the two strengthening techniques using CFRP and concrete jackets can both provide a significant improvement in load-carrying capacity for railway bridge piers with low reinforcement ratio. It is clear that the bottom-anchoring method by using planted steel bars can guarantee the CFRP and concrete jackets to work jointly with original concrete piers Furthermore, it can be found that the use of CFRP jacket offers advantages over concrete jacket in improving the energy dissipation capacity under lateral cyclic loading. Therefore, the seismic strengthening techniques by the use of CFRP and concrete jackets provide alternative choices for the large numbers of existing railway bridge piers with low reinforcement ratio in China.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.117-120
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• 2006

This study is for the strengthening method of continuous bridge through external tendon strengthening that is the most general and effective among concrete bridge's strengthening method. Recently, it is numerous that slab's parts between spans have continuity for improving trafficable ability. However, in this case, slab would have a crack; bridge's durability would be damaged, and also it is too difficult to manage and maintain bridge due to the tensile strength of negative moment. Therefore, the purpose of this study is to demonstrate load-carrying through experiments and develop new external pre-stressing strengthening method for reinforcing continuous bridge.

• Computers and Concrete
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• 제22권2호
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• pp.133-142
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• 2018

The deterioration of existing bridges has become a major problem around the world. In the paper, a new model and an associated stress checking method are proposed for concrete box girders strengthened by external prestressing. The new model called the spatial grid model can analyze all the spatial behaviors clearly by transforming the box girder into discrete orthogonal grids which are equivalent to plate elements. Then the three-layer stresses are employed as the stress checking indices to evaluate the stress state of the plate elements. The initial stress check before strengthening reveals the cracked and potential cracking areas for existing bridges, making the strengthening design more targeted and scientific; the subsequent stress check after strengthening evaluates the strengthening effect and ensures safety. A deficient bridge is selected as the practical example, verifying the accuracy and applicability of the proposed model and stress checking method. The results show that principal stresses in the middle layer of plate elements reflect the main effects of external prestressing and thus are the key stress checking indices for strengthening. Moreover, principal stresses check should be conducted in all parts of the strengthened structure not only in the webs. As for the local effects of external prestressing especially in the areas near anchorage and deviator, normal stresses check in the outer and inner layers dominates and local strengthening measures should be taken if necessary.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.745-750
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• 2001

Considerable research was done to study the fatigue behavior of the reinforced concrete bridge deck which is strengthened by carbon fiber. The purpose of this experimental study is to investigate the fatigue behavior and strengthening effects of the strengthened bridge deck with grid type carbon fiber plastic. The results of this study show that the displacement and the total released energy of strengthening of bridge deck are greater than the case of unstrengthened bridge deck. By strengthening of bridge deck, applied load is so distributed on whole deck member that crack concentration is efficiently controled.

• 콘크리트학회논문집
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• 제14권4호
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• pp.556-565
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• 2002

콘크리트 교량 바닥판은 건조수축 및 온도변화 등에 의하여 초기 일차균열이 발생하고, 사용기간 동안 반복되는 차량하중의 크기와 철근 간격 등에 의하여 초기 균열이 이방향 균열로 점차 진전하게 된다. 바닥판의 거동을 효율적으로 향상시키기 위해서는 보강방향에 대한 고려가 필수적이다. 따라서 본 연구에서는 탄소섬유쉬트를 보강재로 사용한 경우의 보강된 바닥판에 대한 비선형 유한요소해석을 실시하였으며, 해석의 정확성을 높이기 위하여 보강된 바닥판의 경계조건과 재료성질을 시험조건과 부합될 수 있도록 모사하였다. 보강방향과 보강량에 대한 해석결과는 시험결과와 비교, 분석함으로써 정확성을 검증하였으며, 이와 함께 보강된 바닥판의 효율성을 검증하기 위하여 보강재량, 폭과 두께 등과 같은 보강변수에 의한 보강후의 구조적 효율성을 고찰하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.81-86
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• 2001

The concrete bridge decks are in need of replacement and rehabilitation due to decreasing load carrying capacity. In this study, to propose a strengthening technique that improves usability and structural performance of the bridge deck and to propose an efficient strengthening design technique which satisfies both the strength End serviceability of the bridge deck, this paper shows the failure characteristics of the strengthened bridge decks and proposes an empirical yield criterion. Therefore, strengthening efficiency was proposed based on the experiment and yield line analysis result. The yield line theory which adopts the modified criteria of Johansen is considered to predict the ultimate strength about all strengthening material(Carbon Fiber Sheet, Carbon Fiber Rod, Grid Type Carbon Fiber).

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.121-124
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• 2008

FRP를 적용하는 대표적인 보강공법으로는 외부부착공법으로서, FRP Plate 또는 fiber sheet를 사용하여 노후화된 보강면에 FRP 보강재를 부착하는 형식이다. 하지만, 이러한 외부부착공법은 FRP보강재의 인장특성을 충분히 발휘하지 못하는 단점이 있다. 따라서 외부부착공법의 단점을 보완하기 위해 표면매립공법, 즉, Near Surface Mounted(이하 NSM)공법이 제안되었다. 이는 FRP 보강재를 매립함으로써 부재와 보강재의 부착 성능을 증가시킴에 따라 효율적인 응력전달 및 조기 debonding을 사전에 방지할 수 있으며, 이로 인해 FRP 보강재의 인장특성이 효율적으로 발휘될 수 있다. 효율적인 NSM 보강을 위해서는, 구조물에 가해지는 하중, 구성재료, 구조물의 기하학적 형상 등이 갖는 불확실 특성을 반영하여, 보강 후 구조물의 신뢰도를 기준으로 한 보강성능 평가가 필요하다. 본 연구에서는 노후화된 철도교 실교량 모델을 선정하여 외부하중, 재료 및 기하학적 형상의 불확실성을 Monte Carlo Simulation확률기법을 적용하여 그 분포특성을 분석한 후, NSM 보강에 대한한계상태 함수를 통해 목표신뢰도에 부합할 수 있는 휨보강비를 도출하고자 하였다. 해석결과 LS-25하중을 상회하는 내하력 증진효과를 확률분포로써 확인할 수 있었다. 따라서 확률신뢰성기법을 적용한 보강설계의 유효성을 확인할 수 있었으며, 추후 다양한 보강공법으로의 적용이 가능할 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제75권2호
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• pp.271-282
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• 2020

The preservation of historic masonry-arch railway bridges is of paramount importance due to their economic benefits. These bridges which belong to past centuries may nowadays be expected to carry loads higher than those for which they were designed. Such an increase in loads may be because of increase in transportation speed or in the capacity of freight-wagons. Anyway, adequate increase in their load-carrying-capacity through structural-strengthening is required. Moreover, the increasing costs of material/construction urge engineers to optimize their designs to obtain the minimum-cost one. This paper proposes a novel numerical optimization method to minimize the costs associated with strengthening of masonry-arch railway bridges. To do so, the stress/displacement responses of Sahand-Goltappeh bridge are assessed under ordinary train pass as a case study. For this aim, 3D-Finite-Element-Model is created and calibrated using experimental test results. Then, it is strengthened such that following goals are achieved simultaneously: (1) the load-carrying-capacity of the bridge is increased; (2) the structural response of the bridge is reduced to a certain limit; and, (3) the costs needed for such strengthening are minimized as far as possible. The results of the case study demonstrate the applicability/superiority of the proposed approach. Some economic measures are also recommended to further reduce the total strengthening cost.

• 콘크리트학회논문집
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• 제21권6호
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• pp.681-688
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• 2009

철도교량은 일반적으로 공용기간동안 진동과 충격에 의한 구조적 영향을 받는다. 이와 같은 이유로 내하력 증진을 위한 보강성능 검토 시 철도교에 작용하는 외부하중에 효율적으로 저항할 수 있는 보강성능이 요구된다. 이 연구에서는 철도교의 공용 중 진동 및 충격하중에 효율적으로 저항할 수 있는 보강공법으로써 NSM 보강공법을 제안하였다. 이는 기존 탄소섬유외부부착 공법에 비해 부착성능 및 보강성능이 우수한 공법이다. NSM 보강공법은 현재 다양한 실험적 연구들이 진행되고 있으나, 실교량으로의 범용적인 적용을 위해서는 보강설계에 필요한 합리적인 보강비 산정이 필수적이다. 이를 위해, 이 연구에서는 재료적 및 기하학적 불확실성이 반영된 확률 신뢰도기반 NSM 보강비 산정방법을 제안하여 임계보강비를 산정하고자 한다. 이를 위해, Monte Carlo Simulation(MCS) 기법으로 도출된 재료 및 단면치수에 대한 불확실성 특성을 내부저항모멘트 설계식에 반영하여, 외부활하중의 불확실성 특성이 반영된 외부하중모멘트에 대한 안전도 평가를 수행하였으며, 목표신뢰성지수 3.5를 만족할 수 있도록 하는 CFRP 플레이트의 임계보강비를 산출하였다.