• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.16-24
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• 2009

In this study, fatigue crack growth rate of a cracked railway bogie frame under variable amplitude loading is predicted by applying linear elastic fracture mechanics. For this purpose, we find the critical points by reference surveying on cracked railway bogie frames. And we make an effective load history by synthesizing the dynamic load measured from the critical points of railway bogie frame during commercial line operation and the static load calculated from structural analysis. Crack growth analyses are performed at the 3 critical points under the commercial operation loading condition by assuming an initial crack size as 40 mm. and the results are compared with the experimental results from Japanese railway bogie frame crack growth case. From the analysis results, we find that around 500,000 km operating distance is necessary to bring crack growth from the initial crack to unstable crack. And it takes around 3.8 normal operating years. We conclude that it is enough time to detect the crack between normal maintenance period.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.75-82
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• 2015

In this study, experimental research was carried out to evaluate steel reinforced ECC (Engineered Cementitious Composites) column, which exhibits excellent crack control property and highly ductile behavior. Ordinary portland cement and high volume fly ash were used as binding materials in the mixture proportions for the purpose of achieving a high level of multiple cracking property with the tightly controlled crack width. To compare with the cyclic behavior of steel reinforced ECC column specimen, a conventional reinforced concrete column was prepared and tested under reversed cyclic loading condition. Based on the cyclic load test, ECC column exhibited higher cyclic behavior, compared to the conventional RC column, in terms of load carrying capacity and energy dissipation capacity.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.25-28
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• 2008

Generally, reinforced concrete structures exposed to the outside temperature are affected by freezing and thawing process during winter and early spring. These freezing and thawing process can lead to the reduction in durability of concrete as cracking or surface spalling. This paper is to study the hysteretic behavior of RC beams exposed to freezing and thawing under cyclic loadings. To compare the difference in hysteretic behavior of RC Beams, limited tests were conducted under different types of damage and freezing and thawing cycles. For this purpose, six specimens were tested. It is thought that experimental results will be used as basic data to evaluate hysteretic behavior of RC beams exposed to freezing and thawing.

• Journal of the KSME
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• v.16 no.4
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• pp.12-18
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• 1976

기계 및 구조물들이 등진폭하중만을 받는 경우는 극히 드물어서 대부분이 진폭과 주파수가 불규 칙하게 변하는 하중을 받는다. 실하중이력이 불규칙(random)한 모양을 갖는 것은 비행기, 자동차, 선박 등의 많은 기구물들이 공기의 터블런스, 거치론 도로표면 및 대양의 파도와 같이 random한 주위환경에 접하기 때문이다. 이 random한 환경과 구조물의 탄성성질들로 인해서 구조물로부터 측정된 하중응답신호들(응신율,변위 혹은 가속도)은 건폭과 주파수가 random하게 변하는 특정한 형태의 파형을 갖는다. 현금 우리나라에 이 방면의 연구가 활발하지 못하여 complex load history가 피로에 미치는 영향과 이에 관련된 피로시험들을 간략히 소개한다.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.144-151
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• 1997

구조물로부터 측정된 가속도 시간이력을 이용하여 구조손상을 찾아내고 평가하는 기법을 제시하였다. 구조계의 손상을 찾아내는 알고리즘의 주요한 수단으로써 parametric system identification 방법을 사용하였고 매개변수화된 구조물의 최적 매개변수를 추정하기 위해 구속된 비선형 최적화기법을 사용하였다. 손상된 부재를 분리하기 위한 방법으로서 적합적 매개변수 모음법을 적용하였고 손상의 정도를 통계적으로 평가하기 위하여 측정된 가속도 시간이력에 time window 기법을 적용하였다. 가속도 이력 측정에 있어서의 불충분성과 측정오차를 고려하여 알고리즘을 개발하였고, 조화진동하중으로 구조물을 가진하여 구조 손상을 진단하는 수치모의 실험을 실시하였다.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.441-444
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• 2001

PVC로 코팅된 폴리에스테르 섬유로 만들어진 지오그리드 보강재에 대해 변형률을 달리하여 단일 또는 다단 크리프 하중단계를 포함한 하중을 연속적으로 작용시킴으로써 그 인장파괴강도를 검토하였다. 연구결과, 동일한 변형률에서 지오그리드의 인장파괴강도는 극한인장파괴가 되기 전에 작용된 웅력이력에 의해서 거의 영향을 받지 않는다. 또한 지오그리드의 설계파단강도는 적정한 변형률하에서 정의되어야 하며, 변형률 속도가 빠른 인장시험을 통해 지오그리드의 설계파단강도를 얻을 경우 이에 대한 보정이 필요할 것으로 사료된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.217-224
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• 2009

Many engineering researches are performed to ensuring structural safety from earthquake. In this study, the damping capacity of LRB(lead rubber bearing) with high lead-plug area ratio was examined by hysteresis loop from experiments. The displacement controlled tests were performed for 12 specimens designed in 2 types by lead-plug area ratio as main parameter. Each coupled specimens were tested by 3 times sinusoidal loads with different loading velocities. From the experimental results, LRB with high lead-plug area ratio has sufficient damping ratio for reducing horizontal seismic load to structures.

• Journal of Korean Association for Spatial Structures
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• v.10 no.1
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• pp.85-93
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• 2010

This paper suggests a vibration control method long span structures with trussed roof. Basic concept of this method is based on the energy absorption through hysteresis loop of an elasto-plastic element. This element is attached on the top of the column supporting the roof. Two different types of roofs and three of earthquake waves are used in the investigation. It shows that this is very efficient method to reduce the seismic energy of roof member transferred from the column.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1089-1095
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• 2009

The radiated sound pressure induced by tapping test is obtained by solving the Rayleigh integral equation. For structurally radiated sound, the sound field is directly coupled to the structural motion. Therefore the impact response should be analyzed. In this paper, the delamination model is used to analyze the impact response of delaminated composite laminates. And efficient spring-mass model has been proposed to model hammer shaped impactor. Predicted sound pressure histories are compared with test data. The influence of damage on the sound pressure and impacted force history of laminates were investigated. The results show that both radiated sound pressure and impact force history are strongly influenced by delamination on laminates. As a result, it is shown that the presented sound based tapping method was found to be reliable for detecting the damage in composite laminate.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.23-28
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• 1990

지진하중에 의한 콘크리트의 손상 및 파괴의 적절한 평가를 위한 많은 연구가 수행되고 있지만 현재까지 손상을 당한 부재의 잔여강도를 예측할 수 있는 적절한 손상 모델이 없는 실정이다. 본 논문은 콘크리트의 손상에 관한 기본적인 현상들을 면밀히 조사 연구한 후 콘크리트의 low-cycle 피로현상을 해석모델링하여 반복하중 하에서의 손상모델을 제안하였다. 제안된 모델은 콘크리트가 파괴에 도달할 시 싸이클 수 대신에 부재의 흡수에너지 능력을 주요변수로 택하였다. 특히 본 손상모델으 정확성은 기 제안한바 있는 반복하중 작용시의 콘크리트 부재의 해석적인 이력모델[3]을 사용하여 예증하였다.