• Wind and Structures
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• 제11권3호
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• pp.193-208
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• 2008

This paper focuses on assessing the failure of one of the transmission towers that collapsed in Winnipeg, Canada, as a result of a microburst event. The study is conducted using a fluid-structure numerical model that was developed in-house. A major challenge in microburst-related problems is that the forces acting on a structure vary with the microburst parameters including the descending jet velocity, the diameter of the event and the relative location between the structure and the jet. The numerical model, which combines wind field data for microbursts together with a non-linear finite element formulation, is capable of predicting the progressive failure of a tower that initiates after one of its member reaches its capacity. The model is employed first to determine the microburst parameters that are likely to initiate failure of a number of critical members of the tower. Progressive failure analysis of the tower is then conducted by applying the loads associated with those critical configurations. The analysis predicts a collapse of the conductors cross-arm under a microburst reference velocity that is almost equal to the corresponding value for normal wind load that was used in the design of the structure. A similarity between the predicted modes of failure and the post event field observations was shown.

• 대한기계학회논문집A
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• 제24권5호
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• pp.1084-1092
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• 2000

Responses of ultrasonic back scattered energy and AE (Acoustic Emission) characteristics related to the progressive damage of $[0/90-{2}]_s$ and $[0/90-{4}]_s$ crossply laminates were studied. It was found that the ultrasonic backscattered energy was sensitive to the matrix cracking but not sensitive to other failure mechanisms. However, AE was proved to be sensitive to matrix cracking as well as other failure mechanisms.AE signals were analyzed by investigating the amplitude and number of counts per event for corresponding applied strain. Loading and unloading tests were conducted separately. AE results showed Kaiser effect in the crossply composite laminates and ultrasonic results supported the AE results.

• Earthquakes and Structures
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• 제12권5호
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• pp.529-541
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• 2017

According to the definition, progressive collapse could occur due to the initial partial failure of the structural members which by spreading to the adjacent members, could result in partial or overall collapse of the structure. Up to now, most researchers have investigated the progressive collapse due to explosion, fire or impact loads. But new research has shown that the seismic load could also be a factor for initiation of the progressive collapse. In this research, the progressive collapse capacity for the 5 and 15-story steel special moment resisting frames using push-down nonlinear static analysis, and nonlinear dynamic analysis under the gravity loads specified in the GSA Guidelines, were studied. After identifying the critical members, in order to investigate the seismic progressive collapse, the 5-story steel special moment resisting frame was analyzed by the nonlinear time history analysis under the effect of earthquakes with different characteristics. In order to account for the initial damage, one of the critical columns was weakened at the initiation of the earthquake or its Peak Ground Acceleration (PGA). The results of progressive collapse analyses showed that the potential of progressive collapse is considerably dependent upon location of the removed column and the number of stories, also the results of seismic progressive collapse showed that the dynamic response of column removal under the seismic load is completely dependent on earthquake characteristics like Arias intensity, PGA and earthquake frequency contents.

• 터널과지하공간
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• 제16권3호
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• pp.259-276
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• 2006

큰 초기응력을 받는 암반에서의 파괴 과정은 굴착경계에 평행하게 발생하는 응력 유도 균열에 의해 지배된다. 특히 지압의 절대크기가 암반 강도의 일정 비율 이상이 되면 응력 집중에 의한 암반의 취성 파괴를 유발하고, 이러한 현상은 터널 굴착 시 발생하는 파괴음과, 굴착면에 평행한 형태로 암편이 탈락하는 취성파괴 현상을 동반한다. Mohr-Coulomb과 같은 기존의 구성 모델은 일반적으로 마찰각과 점착력을 일정한 값으로 가정하므로, 점진적인 암반의 취성파괴 현상을 모사하기 어렵다. 본 논문에서는 일반적인 수치해석 코드에서 취성파괴를 잘 모의할 수 있는 것으로 알려진 CW-FS 모델을 사용하여 유류 저장공동 주변 암반에 대한 수치해석을 실시하고, 그 결과를 선형 Mohr-Coulomb 모델의 결과와 비교하였다. 또한 마찰각과 점착력 성분의 전단 소성변형률 한계를 변화시키면서 해석을 실시하여, 유류 저장공동에서 관찰된 취성파괴와 비슷한 양상을 보이는 해석 결과를 찾아보았다. 결과적으로 CW-FS 모델은 견고한 암반에서의 취성파괴를 모의하는데 있어 적절한 해석방법이라는 것을 알 수 있었다.

• Communications for Statistical Applications and Methods
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• 제13권1호
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• pp.89-99
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• 2006

This article deals with the problem of estimating parameters of Burr Type XII distribution, on the basis of a general progressive Type II censored sample using Bayesian viewpoints. The maximum likelihood estimator does not admit closed form but explicit sharp lower and upper bounds are provided. Assuming squared error loss and linex loss functions, Bayes estimators of the parameter k, the reliability function, and the failure rate function are obtained in closed form. Finally, a simulation study is also included.

• Communications for Statistical Applications and Methods
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• 제20권6호
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• pp.427-438
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• 2013

Based on progressive Type II censored sampling which is an important method to obtain failure data in a lifetime study, we suggest a very general form of Bayesian prediction bounds from two parameters exponentiated Weibull distribution using the proper general prior density. For this, Markov chain Monte Carlo approach is considered and we also provide a simulation study.

• 한국방재학회 논문집
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• 제4권3호
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• pp.25-31
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• 2004

철도사면은 예상치 못한 연약지반의 존재로 인해 붕괴될 수 있다. 이 연구는 철도사면의 파괴원인을 규명하고 대책공법 적용을 위한 강도정수를 결정하는데 그 목적이 있다. 사면파괴의 원인을 파악하기 위하여 시추조사, 콘관입시험, 현장베인시험 등이 수행되었다. 또한 연약지반의 강도정수를 구하기 위해 불교란상태로 시료를 채취하여 실내시험을 수행하였다. 현장원위치시험 및 실내시험 결과 사면 파괴의 원인은 과압밀점토의 점진적 파괴에 따른 연약지반 강도저하영역의 전파에 기인한 것으로 밝혀졌다.

• Steel and Composite Structures
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• 제23권4호
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• pp.435-444
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• 2017

In the past, the progressive collapse resulting from local failures during accidents has caused many tragedies and loss of life. Although long-span spatial grid structures are characterised by a high degree of static indeterminacy, the sudden failure of key members may lead to a catastrophic progressive collapse. For this reason, it is especially necessary to research the progressive collapse resistance capacity of long-span spatial grid structures. This paper presents an evaluation method of important members and a novel dynamic analysis method for simulating the progressive collapse of long-span spatial grid structures. Engineering cases were analysed to validate these proposed method. These proposed methods were eventually implemented in the progressive collapse analysis of the main stadium for the Universiade Sports Center. The roof of the structure was concluded to have good resistance against progressive collapse. The novel methods provide results close to practice and are especially suitable for the progressive collapse analysis of long-span spatial grid structures.

• 대한한방내과학회지
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• 제24권2_4호
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• pp.1087-1092
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• 2003

Paraquat is a non-selective contact herbicide. When it is consumed, it may cause fatal disorders such as acute renal failure, hepatic dysfunction, and progressive respiratory failure. In spite of many efforts to cure patients poisoned with paraquat, the mortality rate still remain high. In this case, after using Gamdutanghaphwangryunhaedoktang-gamibang and Cheongsangboha-tang we got positive result in hepato-renal function, but progressive respiratory failure was unstoppable.

• Geomechanics and Engineering
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• 제8권1호
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• pp.33-52
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• 2015

Based on the Mohr-Coulomb failure criterion, a gradient-dependent plastic model that considers the strain-softening behavior is presented in this study. Both triaxial shear tests on conventional specimen and precut-specimen, which were obtained from an ancient landslide, are performed to plot the post-peak stress-strain entire-process curves. According to the test results of the soil strength, which reduces from peak to residual strength, the Mohr-Coulomb criterion that considers strain-softening under gradient plastic theory is deduced, where strength reduction depends on the hardening parameter and the Laplacian thereof. The validity of the model is evaluated by the simulation of the results of triaxial shear test, and the computed and measured curves are consistent and independent of the adopted mesh. Finally, a progressive failure of the ancient landslide, which was triggered by slide of the toe, is simulated using this model, and the effects of the strain-softening process on the landslide stability are discussed.