• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.1166-1169
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• 2009

Bridges are exposed to very severe environment and experience, as service life increased, elevated traffic load and traffic flow, in addition to natural disasters. In comparing to other road structures, bridges may cause more significant damage, such as human-involved accidents, to the society in the event of collapse. A certain level of service shall be necessarily secured to assure the minimum safety of users. The cost for manage and preserve bridges will increase gradually and more restrictions will be loaded to efficiently distribute the limited resources, such as monetary budget and human resource etc. In order to enhance performance and serviceability of bridges with the limited resource, asset management technique has been applied into the bridge management system, which capitalizes the road infrastructures including bridges and assess them in accordance with the government finance report. In the application of asset management, there must be a tool for assess the performance of bridges and this study introduces the basic information on the definition and role of performance measures for asset management for bridges. This research suggests future development direction of performance measure for asset management for bridges in Korea.

• Structural Engineering and Mechanics
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• 제53권5호
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• pp.921-938
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• 2015

Realistic prediction of concrete creep is of crucial importance for durability and long-term serviceability of concrete structures. To date, research about the behaviour of self-compacting concrete (SCC) members, especially concerning the long-term performance, is rather limited. SCC is quite different from conventional concrete (CC) in mixture proportions and applied materials, particularly in the presence of aggregate which is limited. Hence, the realistic prediction of creep strains in SCC is an important requirement for the design process of this type of concrete structures. This study reviews the accuracy of the conventional concrete (CC) creep prediction models proposed by the international codes of practice, including: CEB-FIP (1990), ACI 209R (1997), Eurocode 2 (2001), JSCE (2002), AASHTO (2004), AASHTO (2007), AS 3600 (2009). Also, SCC creep prediction models proposed by Poppe and De Schutter (2005), Larson (2007) and Cordoba (2007) are reviewed. Further, new creep prediction model based on the comprehensive analysis on both of the available models i.e. the CC and the SCC is proposed. The predicted creep strains are compared with the actual measured creep strains in 55 mixtures of SCC and 16 mixtures of CC.

• Structural Monitoring and Maintenance
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• 제5권2호
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• pp.243-260
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• 2018

Detection of damages in fibre reinforced plastic (FRP) composite structures is important from the safety and serviceability point of view. Usually, damage is realized as a local reduction of stiffness and if dynamic responses of the structure are sensitive enough to such changes in stiffness, then a well posed inverse problem can provide an efficient solution to the damage detection problem. Usually, such inverse problems are solved within the framework of pattern recognition. Support Vector Machine (SVM) Algorithm is one such methodology, which minimizes the weighted differences between the experimentally observed dynamic responses and those computed using the finite element model- by optimizing appropriately chosen parameters, such as stiffness. A damage detection strategy is hereby proposed using SVM which perform stepwise by first locating and then determining the severity of the damage. The SVM algorithm uses simulations of only a limited number of damage scenarios and trains the algorithm in such a way so as to detect damages at unknown locations by recognizing the pattern of changes in dynamic responses. A rectangular fiber reinforced plastic composite plate has been investigated both numerically and experimentally to observe the efficiency of the SVM algorithm for damage detection. Experimentally determined modal responses, such as natural frequencies and mode shapes are used as observable parameters. The results are encouraging since a high percentage of damage cases have been successfully determined using the proposed algorithm.

• Structural Engineering and Mechanics
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• 제53권6호
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• pp.1183-1200
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• 2015

Reinforcement corrosion can cause serious safety deterioration to aging concrete structures exposed in aggressive environments. This paper presents an approach for reliability analyses of deteriorating reinforced concrete structures affected by reinforcement corrosion on the basis of the representative symptoms identified during the deterioration process. The concrete cracking growth and rebar bond strength evolution due to reinforcement corrosion are chosen as key symptoms for the performance deterioration of concrete structures. The crack width at concrete cover surface largely depends on the corrosion penetration of rebar due to the expansive rust layer at the bond interface generated by reinforcement corrosion. The bond strength of rebar in the concrete correlates well with concrete crack width and decays steadily with crack width growth. The estimates of cracking development and bond strength deterioration are examined by experimental data available from various sources, and then matched with symptom-based lifetime Weibull model. The symptom reliability and remaining useful life are predicted from the predictive lifetime Weibull model for deteriorating concrete structures. Finally, a numerical example is provided to demonstrate the applicability of the proposed approach for forecasting the performance of concrete structures subject to reinforcement corrosion. The results show that the corrosion rate has significant impact on the reliability associated with serviceability and load bearing capacity of reinforced concrete structures during their service life.

• 대한조선학회 특별논문집
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• 대한조선학회 2015년도 특별논문집
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• pp.34-40
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• 2015

The design, procurement and fabrication of FPSO project ordered by Inpex Browse, Ltd. have been currently carried out by DSME(Daewoo Shipbuilding Marine and Engineering Co.). The unit will be installed and operated in the Ichthys field offshore of North-Western Australia and there are the particular design requirements to do with performance on the environment loads corresponding to max. 10,000 years return period wave. Also, the operational life of FPSO has to be over 40 years. With this background, this paper introduces the structural design procedure of crane pedestal foundation operated in north-western Australia offshore. The design of crane pedestal foundation structure is basically based on international design code (i.e. API Spec. 2C), Classification society's rule and project specifications. The design load cases are mainly divided into the crane normal operating conditions and crane stowed conditions according to environment conditions of the offshore with 1-year, 5-year, 10-year, 200-year and 10,000-year return period wave. This design experience for crane pedestal foundation operated in north-western Australia offshore will be useful to do engineering of other offshore crane structures.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.20-27
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• 2009

This paper presents an analytic study for replacement of the ballast track in existing subway bridge by the Precast slab panel(B2S) track. To evaluate the dynamic responses on application of B2S track, the time history analysis with the 3D modeling. A total of two models, which were one ballast track bridge and B2S track bridge, were used in the FE analysis. The results of this study show that the dynamic displacement and acceleration of the B2S track bridge were significantly reduced for a higher train speed, compared to the ballast track bridge. Also, the replacement of the ballast track bridge in existing subway bridge by the B2S track increased the structural safety of bridge and ensured sufficient dynamic stability and serviceability. As a result, the servicing subway bridge with B2S track system has need of the reasonable measures which could be reducing the static and dynamic response and improving the performance.

• 한국철도학회논문집
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• 제16권3호
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• pp.207-216
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• 2013

콘크리트궤도가 부설된 철도교량 단부의 궤도구성품(레일 및 체결구)에는 교량 단부회전에 의해 상향력 및 압축력과 같은 궤도-교량의 상호작용력이 작용하여 손상 및 성능저하가 유발된다. 이러한 교량의 휨거동에 기인한 단부 궤도의 상호작용에 따른 문제를 해결하고자 본 연구에서는 횡단궤도시스템을 개발하고 그 성능을 입증하였다. 횡단궤도시스템의 구조안정성 검토를 위해 3차원 유한요소해석을 통한 시간이력해석을 실시하고 그 결과를 독일의 성능요구조건 및 관련기준과 비교하였다. 또한, 교량-궤도 상호작용 분석을 위한 시험체를 제작하여 실내시험을 수행하고 횡단궤도시스템의 적용 효과를 평가하였다. 연구결과 횡단궤도시스템의 정, 동적 구조안정성 및 횡단궤도 적용 후 교량 단부 궤도의 상호작용력(레일변위, 레일저부응력 및 체결구 응력)이 크게 저감될 수 있음을 실험적으로 입증하였다.

• 대한토목학회논문집
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• 제26권1A호
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• pp.183-190
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• 2006

2거더교를 위한 장지간 바닥판의 설계에서 바닥판의 안전성과 사용성을 만족시키면서 두께를 줄여 자중을 최소화하는 것은 중요한 요소 중의 하나이다. 이 논문에서는 2거더교를 위한 횡방향 프리스트레스트 콘크리트 바닥판의 설계 최소두께와 배근상세를 안정성, 사용성을 고려하여 제시하였다. 대상 교량은, 실용적인 2거더교를 대표할 수 있는 교량으로, 교량길이 40 m의 단순교이다. 대상교량의 바닥판의 지간을 4 m~12m로 변화시켜 가며 분석하였다. 바닥판의 이방성 거동을 고려하여 최소단면을 일방향 슬래브로 설계하고, 균열폭과 피로강도를 평가하였으며, 처짐제한을 충족시킬 수 있는 최소 수준의 두께와 비교하였다. 연구결과, 피로내구성의 확보를 위해서는 직경 16 mm이하의 철근을 사용하는 것이 좋으며, 지간이 8 m를 넘는 장지간 바닥판은 처짐에 대한 사용성이 두께 결정의 지배적 요소임을 확인하였다. 또한, 현행 도로교 설계기준의 배력 철근량 규정을 적용하면 지간 4 m 이상의 바닥판에서는 지간 3 m 이하의 바닥판에서 기대되는 정도의 교축방향의 구조적 연속성을 확보할 수 없는 것으로 나타났다.

• Structural Monitoring and Maintenance
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• 제2권3호
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• pp.283-300
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• 2015

Visual condition inspections remain paramount to assessing the current deterioration status of a bridge and assigning remediation or maintenance tasks so as to ensure the ongoing serviceability of the structure. However, in recent years, there has been an increasing backlog of maintenance activities. Existing research reveals that this is attributable to the labour-intensive, subjective and disruptive nature of the current bridge inspection method. Current processes ultimately require lane closures, traffic guidance schemes and inspection equipment. This not only increases the whole-of-life costs of the bridge, but also increases the risk to the travelling public as issues affecting the structural integrity may go unaddressed. As a tool for bridge condition inspections, Unmanned Aerial Vehicles (UAVs) or, drones, offer considerable potential, allowing a bridge to be visually assessed without the need for inspectors to walk across the deck or utilise under-bridge inspection units. With current inspection processes placing additional strain on the existing bridge maintenance resources, the technology has the potential to significantly reduce the overall inspection costs and disruption caused to the travelling public. In addition to this, the use of automated aerial image capture enables engineers to better understand a situation through the 3D spatial context offered by UAV systems. However, the use of UAV for bridge inspection involves a number of critical issues to be resolved, including stability and accuracy of control, and safety to people. SLAM (Simultaneous Localisation and Mapping) is a technique that could be used by a UAV to build a map of the bridge underneath, while simultaneously determining its location on the constructed map. While there are considerable economic and risk-related benefits created through introducing entirely new ways of inspecting bridges and visualising information, there also remain hindrances to the wider deployment of UAVs. This study is to provide a context for use of UAVs for conducting visual bridge inspections, in addition to addressing the obstacles that are required to be overcome in order for the technology to be integrated into current practice.

• 한국구조물진단유지관리공학회 논문집
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• 제18권4호
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• pp.77-83
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• 2014

PSC거더교는 탁월한 안정성, 사용성 등의 특징으로 전세계적으로 가장 많이 사용되는 교량의 한 형식이다. 그러나, 긴장재 (강연선)의 시공오차나 곡률반경 등에 의하여 절곡되는 상황이 발생하는 경우가 생기며, 이는 국부적인 긴장력의 손실울 유발한다. 그러나, 일반적으로 설계와 시공과정에서는 긴장재의 국부적인 절곡으로 발생하는 긴장력의 손실에 대하여는 간과하고 있다. 이 연구에서는 PSC 거더 연속화 지점부에서 시공오차와 선형반경으로 인하여 발생하는 긴장력 손실량을 실험적으로 규명하였다. 또한, 국부적 긴장력 손실을 감소시킬수 있는 공법을 제안하고 이에 대한 효용을 실험으로 검증하였다. 실험결과에 따르면 국부적 절곡에 의해 최대 10%의 긴장손실이 나타났고, 블록아웃 공법을 통해 손실률을 최대 약 5% 감소시킬 수 있는 것으로 나타났으며, 이는 블록아웃 공법으로 연속화 교량의 긴장효율을 향상시킬 수 있음을 의미한다.