• Title/Summary/Keyword: Long-Term Durability

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An Investigation on the Long Term Durability of High-strength Shotcrete Using Field and Combined Deterioration Test (현장실험과 복합열화시험을 통한 고강도 숏크리트의 장기내구성 검토)

  • Ma, Sang-Joon;Choi, Jae-Seok;Ahn, Kyung-Chul;Kim, Sun-Myung;Kim, Dong-Min
    • Journal of the Korean Geotechnical Society
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    • v.22 no.10
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    • pp.77-91
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    • 2006
  • Domestic practices in shotcrete use have developed in many respects even now, but it still has issues about material, construction, quality standard and so on. In overseas, the construction using high strength shotcrete with $39.2{\sim}58.8 MPa$ of compressive strength is becoming common based on the shotcrete technology of high strength and durability. However, domestic shotcrete design strength is low at around 20.6 MPa of compressive strength and a long term durability is also insufficient. In this paper, field tests using high-quality additives and accelerators were performed to obtain the improvement of shotcrete strength and EFNARC standard was used to evaluate the field test results. In addition, deterioration test combined with the freezing-thawing and carbonation was also performed in order to investigate a long-term durability of high-strength shotcrete. As a result of the field test, the promotion ratio of early strength was $90{\sim}97%$ in case of using alkali-free accelerators. And the compressive strength of the shotcrete using Micro-silica fume was $45.2{\sim}55.8MPa$ and flexible strength was $5.01{\sim}6.66MPa$, so the promotion ratio of strength was $37{\sim}79%$ and $17{\sim}61%$ respectively. The promotion effect of strength by silica fine additives ratio of $7.5{\sim}10%$ for cement mass was much superior to the other cases. It was especially examined that using Micro-silica fume reduced deterioration due to mixed steel fiber and improved a long-term durability of shotcrete.

Long-Term Experiments for Demonstrating Durability of a Concrete Barrier and Gas Generation in a Low-and Intermediate-Level Waste Disposal Facility

  • Kang, Myunggoo;Seo, Myunghwan;Kim, Soo-Gin;Kwon, Ki-Jung;Jung, Haeryong
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.19 no.2
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    • pp.267-270
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    • 2021
  • Long-term experiments have been conducted on two important safety issues: long-term durability of a concrete barrier with the steel reinforcements and gas generation from low-and intermediate-level wastes in an underground research tunnel of a radioactive waste disposal facility. The gas generation and microbial communities were monitored from waste packages (200 L and 320 L) containing simulated dry active wastes. In the concrete experiment, corrosion sensors were installed on the steel reinforcements which were embedded 10 cm below the surface of concrete in a concrete mock-up, and groundwater was fed into the mock-up at a pressure of 2.1 bars to accelerate groundwater infiltration. No clear evidence was observed with respect to corrosion initiation of the steel reinforcement for 4 years of operation. This is attributed to the high integrity and low hydraulic conductivity of the concrete. In the gas generation experiment, significant levels of gas generation were not measured for 4 years. These experiments are expected to be conducted for a period of more than 10 years.

The Parametric Study on the Performance Characteristics of Elastic Rail Fastening System on the Sharp Curved Track (급곡선 탄성레일체결장치의 거동특성에 미치는 매개변수 연구)

  • Baik, Chan-Ho;Joo, Bong-Gyu;Choi, Jung-Youl;Choi, Il-Yoon;Park, Yong-Gul
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.2163-2173
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    • 2011
  • In this study, the deformations and stresses occurred in the elastic rail fastening system were evaluated according to applied extreme track forces based on various field conditions, track curvature and poor properties. The purpose of this study is to establish a method for efficient management and suggest guide line for track construction in order to secure the performance quality of the elastic rail fastening system on the sharp curved track.. Therefore, initial construction qualities of rail and concrete bed, initial clamping force and applied extreme track forces were used into experiment as several parameters. Using these test results, the performance characteristics of the elastic rail fastening system were also evaluated. As a result, it suggested the method to secure long-term durability of fastening system and comparing sharp curved track to results on field test.

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Development and Application of Low Permeable Concrete for Underground Structures (지하구조물을 위한 수밀콘크리트의 개발 및 실용화)

  • Paik, S.H.;Park, S.S.;Park, J.Y.;Paik, W.J.;Um, T.S.;Choi, L.
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.259-262
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    • 1999
  • In underground reinforced concrete structures, such as drainage structure, water and chloride ion penetrated into concrete through the cracks of concrete and its permeable property, cause the corrosion of reinforcing steel bar, which accelerates the expansive cracks and deterioration of concrete. It is necessary to control those deterioration of underground structure by improving its permeability and durability through the reasonable solutions in design, construction and materials. In the present study, fly ash concrete, which has good material properties in long-term period, was compared and studied with plain concrete using ordinary portland cement in terms of fundamental mechanical properties, permeability, drying shrinkage and durability. Also, the mix design and field test of low permeable concrete using fly ash were performed. From this study, fly ash concrete can control the penetration of water and chloride ion effectively by forming dense micro-structure of concrete. Therefore, fly ash concrete may increase the long-term function, performance and serviceability of underground structures.

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A Study on the Reinforcement Corrosion Evaluation of Repair Material and Method for Reinforced Concrete Structure by Long Term Exposure Experiment (장기폭로실험에 의한 철근콘크리트구조물 보수재료$\cdot$공법의 철근부식특성 평가)

  • Kim Young Sun;Lee Eui-Bae;Kim Young Duck;Cho Bong Suk;Kim Jae Hwan;Kim Moo Han
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.197-200
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    • 2005
  • In this study, for the establishment of the performance evaluation methods and the quality control standards of durability recovery method, the quantitative exposure data by long term exposure test under the coast is accumulated and analyzed Investigating and evaluating the result of exposure test at 30 month of exposure age under the coastal environment, carbonation and salt damage are not happened at all but the difference in electric potential are found. Therefore, it is considered that the reinforcement corrosion at replacement with repair material are caused by active-passive corrosion macrocells.

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The analysis on long-term durability and output power characteristics of PV modules by variation on local thermal property (태양전지모듈의 국부적 열특성 변화에 따른 장기적 내구성 및 출력특성 분석)

  • Kang, Gi-Hwan;Kim, Kyung-Soo;Park, Chi-Hong;Yu, Gwon-Jong;Ahn, Hyung-Keun;Han, Deuk-Young
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.214-215
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    • 2007
  • Int this paper, we studied the analysis on long-term durability and output power characteristics of PV modules by variation on local thermal property. Using 5 modules(80W), we measured the maximum output power change during the test period. And the optical transmittance of glass was compared with PV module's maximum power fluctuation. The external environment change effected contamination on the entire or local surface of module. This caused the local temperature variation of each solar cell on PV module. The specific analysis is shown in the following paper.

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A Study on Engineering Characteristics of Geogrids and the Applicability in fields (지오그리드의 공학적 특성 및 설계인자 적용성 평가에 관한 연구)

  • 신은철;김두환;신동훈
    • Proceedings of the Korean Geotechical Society Conference
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    • 1999.03a
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    • pp.105-112
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    • 1999
  • In recent the superior economic benefits and the convenience of installation increased the use of geosynthetics, especially geogrids with the effects of high tensile strength. In this study, various tests were conducted to determine the physical and chemical properties of geogrids which contains durability under various critical conditions, creep behavior and the stability for installation damage in fields. With analysis of test results, the partial and total safety factors were determined and presented the long term design strength of flexible geogrids.

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Long-term simulation of wind turbine structure for distributed loading describing long-term wind loads for preliminary design

  • Ibrahimbegovic, Adnan;Boujelben, Abir
    • Coupled systems mechanics
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    • v.7 no.2
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    • pp.233-254
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    • 2018
  • In order to reduce the dependency on fossil fuels, a policy to increase the production capacity of wind turbine is set up. This can be achieved with increasing the dimensions of offshore wind turbine blades. However, this increase in size implies serious problems of stability and durability. Considering the cost of large turbines and financial consequences of their premature failure, it is imperative to carry out numerical simulations over long periods. Here, an energy-conserving time-stepping scheme is proposed in order to ensure the satisfying computation of long-term response. The proposed scheme is implemented for three-dimensional solid based on Biot strain measures, which is used for modeling flexible blades. The simulations are performed at full spatial scale. For reliable design process, the wind loads should be represented as realistically as possible, including the fluid-structure interaction (FSI) dynamic effects on wind turbine blades. However, full-scale 3D FSI simulations for long-term wind loading remain of prohibitive computation cost. Thus, the model to quantify the wind loads proposed here is a simple, but not too simple to be representative for preliminary design studies.

Probabilistic Durability Analysis of Concrete Structures by Numerical Method (수치해석에 의한 콘크리트 구조물의 확률론적인 내구성 해석)

  • Jung, Sang-Hwa;Kim, Joo-Hyung;Lee, Kwang-Myong;Kim, Jee-Sang;Bae, Su-Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.05b
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    • pp.181-184
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    • 2006
  • Traditional durability analysis is not possible to provide a controlled durability and long-term performance of concrete structures. Recently, research works have shown that probabilistic approach based on the theory of structural reliability, would be very valuable for durability analysis. In this study, the probabilistic durability analysis based on a Monte Carlo Simulation was carried out using sample data selected from detailed field investigation. The probabilistic properties of some design variables, such as diffusion coefficients of concrete and surface chloride concentration, were newly determined using some experimental data. By applying a probabilistic durability analysis to an integral structural design, the durability performance of concrete structures would be remarkably improved.

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A Probability-Based Durability Analysis of Concrete Structures (콘크리트 구조물의 확률론적 내구성 해석)

  • Kim Jee-Sang;Lee Kwang-Myong;Jung Sang-Hwa;Bae Su-Ho;Choi Kyu-Yong;Yang Jong-Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.189-192
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    • 2005
  • In recent years, many research works have been carried out in order to obtain a more controlled durability and long-term performance of concrete structures in chloride containing environments. In particular, the development of new procedures for probability-based durability analysis/design has proved to be very valuable. In this paper, the equation used for modelling of the chloride penetration was based on Fick's Second Law of Diffusion in combination with a time dependent diffusion coefficient. The probability analysis of the durability performance was performed by use of a Monte Carlo Simulation. The procedure was applied to an example based on limited data gathered in this country. The influences of each parameter on the durability of concrete structures are studied and some comments for durability design are given. The new procedure may be very useful in designing concrete structures in chloride containing environments.

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