• 한국자동차공학회논문집
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• 제9권2호
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• pp.143-151
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• 2001

In the recent day, fatigue life prediction techniques play a major role in the design of components in the ground vehicle industry. Full scale durability testing in the laboratory is an essential of any fatigue life evaluation of components or structure of the automotive vehicle. Component testing is particularly important in todey's highly competitive industries where the design to reduce weight and production costs must be balanced with the necessity to avoid expensive service failure. Generally, Multi-axis durability testing device is used to carry out the fatigue test. In this paper, The operation software for simultaneously driving Multi-axis vibration testing device is developed and the input and output data are displayed in windows of PC controller with real time. Moteover the characteristics of the displacement and the load of Multi-axis actuators are calibrated separately.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.597-600
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• 2006

In this study, field survey of carbonation for RC column in city is carried out and carbonation behavior in sound, joint, and cracked concrete is also analyzed. Futhermore, probability of durability failure with time is calculated through considering probability variables such as concrete cover depth and carbonation depth which are obtained from field survey. The probability of durability failure in cracked concrete with considering crack width and time is also calculated and service life is predicted based on intended failure probability in domestic specification. Through this study, it is known that service life in a RC column is evaluated differently for local conditions and each service life is rapidly decreased with decrease in cover depth and increase in crack width.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.84-94
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• 2019

Aluminum substrates are irradiated with chromium ions and the steam condensation heat transfer performance on these surfaces is examined. Filmwise condensation is induced on the surface of aluminum specimens irradiated with chromium ion dose of less than $10^{16}ions/cm^2$ while dropwise condensation occurs on the specimens irradiated with chromium ion dose of $5{\times}10^{16}ions/cm^2$ in the range of ion energy from 70 to 100 keV. The heat transfer coefficient of the surfaces on which dropwise condensation occurs appeared to be approximately twice as much as the prediction by Nusselt's film theory. In a durability test, dropwise condensation lasts over six months and the heat transfer coefficient is also maintained.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 추계 학술논문 발표대회
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• pp.60-61
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• 2019

Concrete carbonation is one of the factors that reduce the durability of concrete. In modern times, due to industrialization, the carbon dioxide concentration in the atmosphere is increasing, and the impact of carbonation is increasing. So, it is important to understand the carbonation resistance according to the concrete compounding to secure the concrete durability life. In this study, we want to predict the concrete carbonation velocity coefficient, which is an indicator of the carbonation resistance of concrete, through the deep learning algorithm, and to find the activation function suitable for the prediction of carbonation rate coefficient as a process to determine the learning accuracy through the deep learning algorithm. In the scope of this study, using the ReLU function showed better accuracy than using other activation functions.

• Journal of Information Processing Systems
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• 제18권4호
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• pp.457-469
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• 2022

Hydraulic concrete buildings in the northwest of China are often subject to the combined effects of low-temperature frost damage, during drying and wetting cycles, and salt erosion, so the study of concrete deterioration prediction is of major importance. The prediction model of the relative dynamic elastic modulus (RDEM) of four different kinds of modified concrete under the special environment in the northwest of China was established using Grey residual Markov theory. Based on the available test data, modified values of the dynamic elastic modulus were obtained based on the Grey GM(1,1) model and the residual GM(1,1) model, combined with the Markov sign correction, and the dynamic elastic modulus of concrete was predicted. The computational analysis showed that the maximum relative error of the corrected dynamic elastic modulus was significantly reduced, from 1.599% to 0.270% for the BS2 group. The analysis error showed that the model was more adjusted to the concrete mixed with fly ash and mineral powder, and its calculation error was significantly lower than that of the rest of the groups. The analysis of the data for each group proved that the model could predict the loss of dynamic elastic modulus of the deterioration of the concrete effectively, as well as the number of cycles when the concrete reached the damaged state.

• 한국건설순환자원학회논문집
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• 제7권3호
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• pp.56-61
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• 2012

콘크리트의 열화는 현재 전세계적인 관심 분야로서 가장 보편적인 열화원인은 염해이다. 이를 고려한 내구수명 예측기법의 개발은 토목건설 기술에 매우 중요한 부분을 차지하고 있으나, 대부분의 기존의 연구는 수명예측에 대한 기법에 집중되어 왔을 뿐, 콘크리트 표면의 미세 기후조건을 고려한 환경 분석은 매우 드문 실정이다. 그러나 콘크리트의 내구성은 표면의 특성에 의해 지배되므로, 실질적으로 표면상태에 대응한 미세 기후조건을 연구하여 환경대응 인자로 정립할 필요가 있다. 본 연구는 현장 기후조건을 계측하여 콘크리트의 미세기후조건을 해석할 수 있는 방법을 제안하였다. 이 결과는 염소이온 확산계수와 같은 재료 매개변수에 반영하여 더욱 정밀한 수치 해를 얻는데 이용되었다. 본 연구는 콘크리트의 내구성 설계기법을 개발하기 위하여, 환경인자에 대응한 매개변수를 도출하는데 이용될 수 있을 것으로 기대된다.

• Steel and Composite Structures
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• 제31권1호
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• pp.69-83
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• 2019

This paper investigates the structural behavior of very high strength concrete encased steel composite columns via combined experimental and analytical study. The experimental programme examines stub composite columns under pure compression and eccentric compression. The experimental results show that the high strength encased concrete composite column exhibits brittle post peak behavior and low ductility but has acceptable compressive resistance. The high strength concrete encased composite column subjected to early spalling and initial flexural cracking due to its brittle nature that may degrade the stiffness and ultimate resistance. The analytical study compares the current code methods (ACI 318, Eurocode 4, AISC 360 and Chinese JGJ 138) in predicting the compressive resistance of the high strength concrete encased composite columns to verify the accuracy. The plastic design resistance may not be fully achieved. A database including the concrete encased composite column under concentered and eccentric compression is established to verify the predictions using the proposed elastic, elastoplastic and plastic methods. Image-oriented intelligent recognition tool-based fiber element method is programmed to predict the load resistances. It is found that the plastic method can give an accurate prediction of the load resistance for the encased composite column using normal strength concrete (20-60 MPa) while the elastoplastic method provides reasonably conservative predictions for the encased composite column using high strength concrete (60-120 MPa).

• 한국산학기술학회논문지
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• 제19권10호
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• pp.424-429
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• 2018

본 연구에서는 플랜트 설비 부품류 중 충격에 취약한 신축관 이음을 대상으로 수충격 발생 시 신축관 이음의 신축량을 유압식 액추에이터의 작동데이터로 적용하여 진동내구 시험을 수행하였다. 진동내구 시험 시 내구수명의 가속 요소로 신축관 내부의 온도상태를 가정하고 온도상태를 $30^{\circ}C$부터 $50^{\circ}C$ 및 $65^{\circ}C$로 가속화한 진동내구 시험을 진행하였다. 각 조건별 온도상태별 수명데이터들은 아레니우스 모델식을 따른다고 가정하고 각 수명데이터를 선형화하여 선형식의 상수값과 활성화 에너지 계수를 유도하였다. 또한 유도된 모델식으로부터 $85^{\circ}C$ 경우의 예측 수명과 $85^{\circ}C$ 온도상태에서의 시험 수명결과와 비교를 통해 작은 편차 범위내에서 유도된 모델식의 유효성을 검증하였다. 한편, 시험 중과 시험 후 발견된 신축관의 고장모드에서는 누수 및 벨로우즈 부 내부 슬리부의 이탈과 내부변형 등을 확인할 수 있었다. 향후 본 연구는 진동내구 수명의 가속요인인 온도상태 외 압력상태 등 다양한 수명변수를 적용한 복합수명예측 모델식을 개발하고 검증할 예정이다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.555-558
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• 2001

Carbonation of concrete decreases durability of RC structures due to failure of passive film of rebar. Therefore, expecting carbonation depth is a governing parameter of service life prediction for RC structures. This study attempt to estimate carbonation depth quantitatively by using equivalent effective diffusion coefficient of $CO_2$.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.169-172
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• 1995

Establishment of a diagnosing technology for the deterioration of reinforced concrete structures due to salt contamination is urgent, but few analytical methods based on measured data obtained from concrete structures have been presented so far. Chloride penetration into concrete from sea water is generally understood and analysed as diffusion of chloride ion. This paper presents a new method of predicting chloride penetration into concrete based on diffusion theory. Also, it determines the duralility of Marine structure in service with the prediction of remaiing lifetime by the carvonation test.