• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.322-329
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• 2016

This study is about the method to control the quality of material used to repair leakage and crack of concrete structure and suggests the "Temperature Stability Test Method" as a follow-up study. In the result of performance evaluation for 45 samples of 15 types in 5 series, the temperature stability test showed different material changes including rolling down, volume change, and color change as they are frozen and melt repeatedly in the somewhat extreme conditions at low($-20^{\circ}C$) and high($60^{\circ}C$) temperatures, where 13 samples (approx. 29%) and 32 samples (approx. 71%) showed leakage, respectively, in the permeability test to evaluate leakage. This result shows the enough importance of setting the quality control criteria of leakage repair material currently used to maintain concrete structures considering the temperature conditions, and proves the applicability of the Temperature Stability Test Method as a standard test method to ensure long-term durability of concrete structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.317-324
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• 2020

In this study, a simplified equation for settlement evaluation suitable for the special conditions of a counter facility is suggested. Recently, counter facilities, especially breakwaters, are constructed on soft ground in distant seas as new-port development projects. A counter facility that resists the external forces by self-weight settles easily when constructed on soft ground. Settlement in a counter facility and breakwater is not an important factor for maintenance than a land facility. On the other hand, the current settlement evaluation criteria are excessive for conducting a safety inspection. A settlement evaluation from a safety inspection followed by "Detailed Guidelines for a safety inspection on a counter facility" is used. A simplified equation was proposed to calculate the maximum settlement by applying the allowable residual settlement or settlement stability evaluation results. The suitability of the simplified equation was assessed compared to the assessed rating from the settlement survey results. The proposed simplified equation showed that the settlement evaluation rating had been upgraded. The proposed simplified equation is expected to be used to evaluate the practical structural stability and functional performance.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.105-115
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• 2016

This paper describes a restoration of retaining wall, which was collapsed by rainfall. The failure causes was analyzed by field case, and then the countermeasure was suggested. The failure causes confirmed that observance of design and construction criteria was insufficient. It also was the climate condition like a rainfall and inappropriate construction management. The stability analysis for retaining wall, soil improvement and reinforced earth wall was conducted to confirm validity of the countermeasure. The analysis results showed that the suggested construction method satisfied in required safety factors. Therefore, it should be secured the stability of the structure based on the application of appropriate design method and construction management, when structure was constructed.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.81-92
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• 2011

In order to understand evaluation of the seismic stability of a fill dam, we made chambers of 1:100, 1:70, and 1:50 (the ratio of the miniature), considering the law of similarity based on drawings of three representative cross sections. And we measured an increase in acceleration, excess pore water pressure, and vertical/horizontal displacement after applying Hachinohe wave (long period), Ofunato wave (short period), and artificial wave, complying with the domestic standards, in order to evaluate the stability and interaction between the ground, the structure, and fluids based on the measurements. As a result, we could observe that displacement of the target cross section was relatively small compared to the allowed level of 30 cm, ensuring proper stability for an earthquake. Regarding the acceleration measurements, the increase rate was 20% for Hachinohe wave and Ofunato wave but 30% for the artificial wave. With respect to the excess pore water pressure, it was lower than 1 (which is the permissible ratio for liquefaction) ensuring proper stability as well.

• Journal of the Korean Geosynthetics Society
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• v.10 no.3
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• pp.53-62
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• 2011

This paper presents the characteristics behavior of dike structure and foundation ground through the shaking table model test. The vibration loadings of design earthquake acceleration of 0.154g was applied to this laboratory model test regarding on dike structure and foundation ground under the structure. The model was formulated with 1/100 design of representative cross section for evaluating the effectiveness of vibration. Based on the test results, we can analysis the behavior of lateral displacement and settlement characteristics of structure under the earthquake loading. The pore water pressure was also monitored in the upper, middle and lower layers of ground. Finally, the actual displacements and pore water pressure of the structure can be predicted by using the results of the laboratory shaking table test.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.95.2-95.2
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• 2012

고온형 SOFC의 개발에 있어 스택의 신뢰성을 확보하는데 가장 중요한 핵심기술은 스택 구성요소 사이를 접합하는데 필요한 고온형 밀봉재의 개발이다. SOFC 스택에서의 밀봉재는 고체전해질과 접속자 사이에서 음극에 공급되는 연료가스와 양극에 공급되는 공기가 서로 혼합되는 것을 방지하는 역할은 물론 기계적으로 취약한 단전지의 보호 및 스택전체 구조물의 구조적 일체성(Structural integrity)을 부여하는데 주목적이 있다. 현재 기체 기밀성을 유지하기 위한 밀봉재는 크게 유리 및 결정화 유리계, mica및 mica/유리복합재료, 유리/충전재 복합재료 등이 사용되고 있으나 다수의 단위전지로 구성되는 스택 구성에서 스택의 열기계적 안정성 및 장기수명을 보장하기 위해서는 본 연구에서 개발하고자 하는 복합밀봉재가 가장 적합할 것으로 예상되고 있다. 본 연구에서는 SiO-B2O3-RO계에 BaO, SrO를 일정비율로 첨가하여 제작된 유리 frit을 열처리하여 물리화학적 물성변화를 검토하였으며, $750^{\circ}C$ 이하의 연화점을 갖는 유리를 기지상으로 하고 세라믹 보강재를 첨가한 고온형 복합밀봉재를 개발하고 그 물리화학적 안정성, 열기계적 안정성 및 밀봉 특성을 평가하였다.

• Journal of the Korean GEO-environmental Society
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• v.23 no.11
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• pp.13-18
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• 2022

In this study, the suitability of the grouting method will be evaluated by analyzing seismic reinforcement methods for the stability of gravity structure in Port. The evaluation categories are liquefaction, sliding, toppling and circular failure. To compare the appropriateness of the seismic reinforcement method, the low mobility mortar injection, one of the grouting method and the SPC file and GRB method, which are pile wall type reinforcement methods, were evaluated and compared respectively. The object of the evaluation is the gravitational structure of Po-Hang old port. As a result of the evaluation, both the grouting method and the pile wall type reinforcement method are considered to have sufficient stability. Therefore, in the case of the gravity structure, the grouting method is more efficient than the seismic reinforcement method considering construction efficiency, economic efficiency, maintenance and similar construction cases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.13-15
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• 2014

최근 경제적인 연비와 효율적인 가동성, 배기가스 감소의 이유로 초임계압 보일러가 각광받고 있다. 하지만 보일러 연소로는 용접된 튜브로 구성되어 있기 때문에 연소 시 내부압력에 의해 발생되는 진동에 취약하여 이에 대한 진동안정성 평가가 필요하다. 본 논문에서는 CFD 기법을 기반으로 수행한 변동압력 해석과 단순화한 모델을 이용한 진동해석을 통하여 보일러 운전 시의 진동안정성 평가를 수행하였다. 변동압력해석은 정상상태 CFD 해석을 수행하고, 이를 이용한 음향모드 해석과 비정상상태 CFD 해석에서 변동압력을 추출하고, 음향모드 해석결과와 주파수 성분을 비교하여 검증하였으며 이를 진동해석 모델에 기진력으로 적용하여 보일러 연소로의 진동해석을 수행하였다. 진동해석 모델은 동특성을 고려한 등가물성치를 이용하여 연소로의 복잡한 구조를 단순화하였으며 buckstay 등의 방진구조를 구현하여 보일러의 진동안정성을 평가하는 기법을 정립하였다. 해석결과, 보일러 운전조건에서 비정상상태 CFD 해석을 통해 구한 변동압력과 진동해석을 통해 얻은 가속도 응답은 안정적 수준인 것으로 확인하였다. 이는 향후 유사한 보일러 안정성 평가에 적용이 가능하고, buckstay 등 보일러의 방진 구조 설계 및 평가에도 적용할 수 있음을 확인할 수 있었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.5
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• pp.47-56
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• 2001

In order to assure the safety of NPP structures, margin of safety or conservatism is incorporated in each design step. Seismic risk evaluation of NPP structures is performed based on the realistic capacity and response of structure eliminated the safety margin and conservatism. In this study, the comparative study on the various evaluation methods of the inelastic energy absorption capacity was performed. The inelastic energy absorption capacity due to the nonlinear behavior of structures has significant effect on the results of seismic probabilistic risk assessment. And the comparison study of the HCLPF(high confidence of low probability of failure) values according to the inelastic energy absorption factors was performed. As a conclusion, the inelastic energy absorption factor of NPP containment structure is estimated about 1.5~1.75. It is essential to estimate the nonlinear behavior of structure and its ductility factor correctly for the seismic risk assessment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1283-1290
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• 2014

Recently, a wide variety of simulation techniques such as structure analysis and structure-fluid interaction analysis are being employed in the field of forensic engineering for resolving the problem of legal liability for accidents and disasters. In this study, we performed a forensic engineering investigation of a sinking accident of a DCM (deep cement mixing) vessel. The accident vessel was built as a dedicated SCP (sand compaction pile) vessel at the time of vessel building, and the DCM vessel was structurally modified, e.g., by increasing the leader height and constructing for leader expansion, without a stability review. To determine the effects of expansion and modification of structures in this sinking accident, structural stability evaluation was performed using commercial software for structural analysis, ADINA software. Through an analysis and comparison of simulation results obtained using ADINA software with the results of the structural modification and expansion, we could determine the exact cause of the sinking accident of the DCM vessel.