• Ecology and Resilient Infrastructure
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• v.3 no.2
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• pp.117-125
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• 2016

Current cities encounter various types of water problems due to rapid urbanization and climate change. The increasing significance of urban water problems calls for the establishment of resilient alternatives to prevent and minimize social loss that results from these phenomena. As a background research for establishing resilient infrastructures for the mitigation of urban water problems, we evaluated the robustness of structural alternatives for urban flood as a representative case. Combining the robustness index (RI) and the cost index (CI), we suggested the robustness-cost index (RCI) as an indicator of the robustness of structural alternatives, and applied the index to assess the existing infrastructures and structural alternatives (i.e., sewer network expansion, additional storage tank construction, and green roof construction) at a site prone to floods located around Gangnam-station, Seoul, Korea. At a rainfall intensity frequency range of 2 to 20 years, the usage of a storage tank and a green roof showed relatively high RCI value, with a variation of an alternative showing greater RCI between the two depending on the size of design rainfall. For a rainfall intensity frequency of 30 years, installing a storage tank with some green roofing was the most resilient alternative based on the RCI value. We proposed strategies for establishing resilient infrastructures for the mitigation of urban floods by evaluating the robustness of existing infrastructures and selecting optimal structural alternatives with the consideration of scales of design disaster.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.191-196
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• 2020

In this study, the durability was analyzed as the models with three shapes depending on the length of the landing gear. Overall, the upper part of the landing gear produced a greater amount of deformation, but the equivalent stress was shown to be high in the upper part just above the lower part. Model 3 shows that the maximum equivalent stress is more than 4 times and the maximum total deformation is more than 24 times compared to model 2. Model 3 showed that the damage could occur beyond the yield stress at the lower end. Model 2 with the upper part longer than the lower part showed the lowest equivalent stress and total deformation among the three models. Therefore, from a structural standpoint, it was shown that model 2 was the most durable at landing and model 3 was the most degraded in terms of durability. The design and analysis results of this study can be effectively applied at grasping the structural durability of landing gear. By applying the structural durability analysis of landing gear, this paper is seen as the convergence study that conforms to aesthetic design.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.67-74
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• 2015

RC (Reinforced Concrete) structures are considered as cost-benefit and durable however performances of structural safety and durability are degraded due to steel corrosion. Service life in RC structure is differently evaluated due to different local environmental conditions even if it is exposed to the same chloride attack. In the paper, 25 concrete cores from field investigation are obtained from 4 RC columns with duration of 3.5~4.5 years exposed to sea water. Through total chloride content measurement, surface chloride contents and apparent diffusion coefficients are evaluated. Service life of the target structure is estimated through deterministic method based on Fick's $2^{nd}$ Law and probabilistic method based on durability failure probability, respectively. Probability method is evaluated to be more conservative and relatively decreased service life is evaluated in tidal zone and splash zone over 40.0 m. Chloride penetration behavior with coring location from sea level and the present limitations of durability design method are investigated in the paper.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.343-352
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• 2010

Recently, many researchers have been carried out to estimate more controlled service life and long-term performance of carbonated concrete structures. Durability analysis and design based on probability have been induced to new concrete structures for design. This paper provides a carbonation prediction model based on the Fick's 1st law of diffusion using statistic data of carbonated concrete structures and the probabilistic analysis of the durability performance has been carried out by using a Bayes' theorem. The influence of concerned design parameters such as $CO_2$ diffusion coefficient, atmospheric $CO_2$ concentration, absorption quantity of $CO_2$ and the degree of hydration was investigated. Using a monitoring data, this model which was based on probabilistic approach was predicted a carbonation depth and a remaining service life at a variety of environmental concrete structures. Form the result, the application method using a realistic carbonation prediction model can be to estimate erosion-open-time, controlled durability and to determine a making decision for suitable repair and maintenance of carbonated concrete structures.

• Information Display
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• v.20 no.3
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• pp.48-56
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• 2019

유연 OLED 디스플레이 구현을 위한 박막 봉지 기술에 대해 두 가지 관점으로 살펴보았다. 첫 번째 다층 구조를 통한 박막 봉지 특성 개선에 대한 연구는 현재까지 다양한 연구들이 진행되어 왔으며 활발히 진행 중이다. 특히 우수한 투습 방지 특성을 가지며 동시에 기계적 내구성을 잃지 않기 위해 유 무기 적층구조는 중요한 연구 주제였다. 유기물 층은 다양한 소재, 증착 방법들이 연구되었으며 무기물 층은 ?고 좋은 특성을 가지기 위해 원자층 증착법을 활용하는 것이 중요하다. 특히 원자층 증착법이 대면적 증착이 가능하며, 균일도가 높다는 점에서 향후 양산에서도 활용이 가능하다는 점에서 원자층 증착법과 분자층 증착법을 통한 유 무기 적층 구조 연구가 중요하다고 할 수 있다. 또한 막에 구조적인 변화를 주어 가해자는 응력을 최소화하는 방법을 소개하였다. 이론적으로 전체막에서 외부 응력이 가해지더라도 받는 응력이 0이 되는 중립면을 활용하면 큰 외부 응력이 막에 가해지더라도 열화가 확연히 줄어든 연구 결과들이 있었다. 결론적으로 유연 OLED 디스플레이 구현하기 위해 박막 봉지 측면에서 이루어 져야 할 연구의 방향은 소재적으로 유 무기 적층 구조를 통한 막 내구성 및 투습 방지 특성 확보가 중요하고 구조적으로는 OLED 패널 제작 시 박막 봉지 층 이외에 상부 추가되는 막의 두께와 탄성 계수를 조절하여 기계적 내구성이 낮은 백플레인 부분과 박막 봉지 부분을 중립면에 위치시켜 외부 응력으로부터 자유로워 지도록 하는 방향으로 진행될 것으로 예상된다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.969-974
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• 2008

This study was carried out to investigate the service life of reinforced concrete structures for durability design. The service life has three aspects physical service life, functional service life, and social service life, and that a structures are normally demolished to end its service life when either the functional or social service life is over before the physical service life comes to end an end. In the future, it is very important that durability design shall be performed establishing design service life and the unallowable state of deterioration in the course of design service life.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.211-220
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• 2005

The concrete structure is being considered for the main engineered barrier of low and intermediate level radwaste disposal facility. Concrete of low permeability can minimize infiltration of water and effectively prevent release of nuclide to ecosystem. But if concrete degrades, structural stability of disposal structure will decrease while permeability increase, resulting in increased possibility of nuclide release due to water infiltration. Therefore disposal concrete structure degradation shall be minimized to maintain capacity of nuclide isolation. The typical causes of concrete structure degradation are sulfide attack, reinforcement corrosion due to chloride attack, leaching of calcium hydroxide, alkali-aggregate reaction and repeated freezing-thawing. The common cause of these degradation processes is infiltration of water or adverse chemicals into concrete. Based on the study of these degradation characteristics and mechanisms of concrete structure, the methodology of design and service life evaluation of concrete structure as an engineered barrier are reviewed to ensure its long-term durability.

• Magazine of the Korea Concrete Institute
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• v.14 no.3
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• pp.71-76
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• 2002

콘크리트는 거의 반영구적인 재료라고 인식되어져 왔으나, 최근들어 해양환경, 적설한랭지대, 도심과 같은 열악한 환경속에서 예상보다 빨리 조기열화 되는 현상이 널리 알려지면서 콘크리트 구조물의 구조적 성능뿐만 아니라, 장기적인 내구성에 대한 관심이 높아져 가고 있다. 실제로 여러 선진국에서 염해와 같은 열화환경의 피해를 받은 콘크리트 구조물이 예상공용년수 이전에 철거되거나. 개보수 비용이 초기 건설비용보다 더 많이 드는 예가 적지 않게 보고되면서, 적절한 내구성 유지대책 및 구조물의 장수명화를 위해 많은 연구와 노력이 진행되고 있다.(중략)

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.239-248
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• 2006

Recently, a variety of researches has been carried out to obtain a more controlled durability and long-term performance of concrete structures under chloride attack environments. In particular, new procedures for probability-based durability analysis/design have been noticed to be very valuable for the enhancement of service life of concrete structures. Although there is still a lack of relevant data, this approach has been successfully applied to some new concrete structures. In this paper, the diffusion equation based on Fick's second law has been solved with a time dependent diffusion coefficient and the probabilistic analysis of the durability performance has been carried out by using a Monte Carlo Simulation. From the results, the influence of each parameter on the durability of concrete structures was investigated and the new procedure for durability analysis was demonstrated in terms of chloride penetration data from various concrete structures. The new procedure might be very useful in designing important concrete structures and help to predict the remaining service life of existing concrete structures under chloride attack environments.

• Ecology and Resilient Infrastructure
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• v.3 no.3
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• pp.182-188
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• 2016

This study evaluated structural alternatives for managing water quality problems by reinterpreting and then applying the robustness-cost index (RCI) for urban flood problems. Cases of endogenous hormone pollution in treated sewage and proliferation of protozoa in intake-water were chosen as representative examples because they have different types of regulation standards for the treatment. Current facilities and structural alternatives with robustness indices (RIs) greater than unity were determined to be robust. The RI was combined with the cost index (CI) to obtain the RCI values. For the endogenous hormone pollution in treated sewage, a human-oriented estrogen $17{\beta}$-estradiol was selected as a target pollutant. The RI and RCI values for a structural alternative, extension of the current sewage treatment facility for advanced treatment, were greater than the values for the current practice of conventional activated sludge process. For the intake-water pollution by protozoa, UV and ozone disinfection facilities were evaluated for inactivation of Cryptosporidium parvum. The RCI values for ozone disinfection were greater than those for UV disinfection. Based on the results and the logics involved in the calculation of RCI for water quality issues we studied, we proposed procedures for establishing and implementing structural alternatives for the restoration from and prevention of outbreaks of water quality problems.