• International Journal of Naval Architecture and Ocean Engineering
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• 제10권1호
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• pp.21-36
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• 2018

The incidence of collision damage models on oil tanker and bulk carrier reliability is investigated considering the IACS deterministic model against GOALDS/IMO database statistics for collision events, substantiating the probabilistic model. Statistical properties of hull girder residual strength are determined by Monte Carlo simulation, based on random generation of damage dimensions and a modified form of incremental-iterative method, to account for neutral axis rotation and equilibrium of horizontal bending moment, due to cross-section asymmetry after collision events. Reliability analysis is performed, to investigate the incidence of collision penetration depth and height statistical properties on hull girder sagging/hogging failure probabilities. Besides, the incidence of corrosion on hull girder residual strength and reliability is also discussed, focussing on gross, hull girder net and local net scantlings, respectively. The ISSC double hull oil tanker and single side bulk carrier, assumed as test cases in the ISSC 2012 report, are taken as reference ships.

• 한국지반신소재학회논문집
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• 제16권1호
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• pp.41-52
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• 2017

본 연구에서는 월류에 의한 붕괴 메커니즘의 규명을 위해 모형제방(제방고 0.4~0.8m)과 실물제방(제방고 1.0m)을 대상으로 월류 붕괴실험을 수행하였다. 월류에 의한 제방붕괴는 1단계에서는 월류에 의해 비탈표면에서 세굴이 발생되었으며, 월류의 유속은 완만히 증가되었다. 2단계에서는 붕괴단면이 커지고 유속도 급격히 증가되었다. 3단계에서는 월류에 의해 제방 단면이 완전히 붕괴되고 붕괴면적이 넓어져 유속이 상대적으로 감소되었다. 월류에 의한 제방의 붕괴각(${\theta}$)은 큰 자중, 감소된 전단저항력 및 월류의 흐름에 의한 추가 소류력으로 인해 랭킨토압의 사면붕괴각보다 크게 나타났다. 제방고(H)가 증가될수록 월류에 의한 제방의 월류 유속(${\upsilon}$)이 증가되었으며, 이로 인해 소류력이 추가로 작용되어 제방의 붕괴각(${\theta}$)과 붕괴면적(A)이 함께 증가되었다. 모형실험과 실물실험에 사용된 모래 시료가 동일한 입경크기로 한계세굴유속이 같아 월류 유속변화에 의해 세굴 특성이 지배되는 것으로 나타났다.

• 한국콘텐츠학회논문지
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• 제18권3호
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• pp.472-485
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• 2018

본 연구는 용인시의 채무제로화 정책과정을 Kingdon의 다중흐름모형을 통해 분석하여 지방정부의 재정역량 강화 및 경쟁력 제고에 기여하고자 하였다. 용인시는 2012년 기준 약 8,000억원의 지방채무를 가지고 있었으나 2017년 초 채무상환을 완료하였다는 점에서 분석대상으로 선정하였다. 분석 결과 첫째, 정책문제의 흐름은 용인시의 채무지표에 대한 인식, 경전철사업의 실패 및 역북지구의 택지분양 실패이다. 둘째, 정치의 흐름은 새로운 지방자치단체장의 당선과 공무원 예산 삭감 등의 행정부 협조, 주민들의 협조로 볼 수 있다. 셋째, 정책대안의 흐름은 대규모 투자사업 축소, 유휴공유 재산 매각을 통한 세입확대 및 세수증대, 경전철 활성화 정책이다. 이러한 정책문제의 흐름, 정치흐름, 정책대안의 흐름이 독립적으로 흐르다가 부동산경기 활성화와 역북지구 매각이라는 정책의 창이 열리면서 경전철 활성화 등의 기타 정책적 요소와 결합하였다. 이 과정에서 긴축재정을 위한 관계기관 협상과 설득 등의 정책선도가의 역할이 크게 작용하였다. 이러한 정책의 산출물로써 용인시는 채무제로를 달성하게 되었다. 본 연구를 통해 지방재정 역량 제고를 위해서 정책선도가의 역할의 중요성 뿐만 아니라 행정부와 시민의 협조, 대형 투자사업 추진 검토체계 등의 제도적 보완이 필요함을 밝혔다.

• 한국통신학회논문지
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• 제16권11호
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• pp.1167-1178
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• 1991

전투지역 환경의 특징을 조사하고 요구되는 네트워크 성질을 고려하여 그 성질에 적합한 네트워크 제어구조를 설계한다. 또한 네트워크의 제어구조를 구성하며 제어구조에서 형성된 근간 네트워크에서의 전송계획을 작성하기 위한 분산 제어 알고리즘을 설계한다. 전투지역에서 변화하는 네트워크의 연결성 유사와 노드의 파괴로 인한 네트워크의 즉각적인 재구성을 신뢰성 있게 하기 위한 분산 알고리즘과 또한 공통 채널을 이용하는 네트워크에서 노드간에 전송충돌이 없는 전송 계획은 작성하기 위한 분산 알고리즘을 제안한다. 특히 중요한 노드가 파괴 및 사라질 때 되도록 적은 지연을 통해 네트워크가 동작할 수 있는 방법을 제안한다. 그리고 제안된 분신 알고리즘을 시뮬레이션을 통해 검증하고 네트워크 동작에 관해 설명한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1130-1135
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• 2003

The need to increase the reliability of a structural system has been significantly brought in the procedure of real designs to consider, for instance, the material properties or geometric dimensions that reveal a random or incompletely known nature. Reliability based design optimization of a real system now becomes an emerging technique to achieve reliability, robustness and safety of these problems. Finite element analysis program and the reliability analysis program are necessary to evaluate the responses and the probabilities of failure of the system, respectively. Moreover, integration of these programs is required during the procedure of reliability based design optimization. It is well known that reliability based design optimization can often have so many local minima that it cannot converge to the specified probability of failure. To overcome this problem, barrier function method in reliability based design optimization is suggested. To illustrate the proposed formulation, reliability based design optimization of a bracket is performed. AMV and FORM are employed for reliability analysis and their optimization results are compared based on the accuracy and efficiency.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.237-242
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• 2001

Residual stress is a dominant obstacle to efficient production and safe usage of products by reducing the mechanical strength and failure properties. Especially, it causes interfacial failure and substrate deflection in the case of thin film. So, the exact evaluation and optimum control of thin film residual stress is indispensable. However, hole drilling or X-ray diffraction techniques have some limits in application to thin film. And, curvature technique for thin film materials cannot give the information about local stress variation. Therefore, we applied the nanoindentation technique in evaluating the thin film residual stress. In this study, we modeled the change of indentation loading curve for residually stressed and stress-free thin films during stress relaxation. The value of residual stress was directly related to the indentation depth change by relaxation. The residual stress from nanoindentation analysis was consistent with the result from curvature technique.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.111-118
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• 2002

Recent study of soft clay of Nakdong-River basin has been taken correlation between soil properties by regression analysis without distribution whether the sample is disturbed or not, or treated as a whole area without proposing local correlation equation to Jang-U or Dae-Joe which has a specific locality. Accordingly, Those tendency cause the reliability of correlation between compression index and void ratio low and then design underestimate and uncertain eventually. In this study, Distributing the soft clay of Nakdong-River basin with failure strain of 6%, the suggestion by Skempton(1957), TakeNaka(1966)-the more sample is undisturbed, the more the ratio of E$\_$50/ and ｑ$\_$u/, ${\alpha}$ = E$\_$50//(q$\_$u//2) = 1/$\varepsilon$$\_$50/ is high-is satisfied with the value of which ${\alpha}$ is 50 and It could be taken enough data in the condition of domestic. Besides other indices also make the distribution suitable. In conclusion, This study is supposed to propose the locally subdivided regression equation between compression index and void ratio considering the sample disturbance.

• Earthquakes and Structures
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• 제13권1호
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• pp.67-77
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• 2017

Oil storage tanks are vital life-line structures, suffered significant damages during past earthquakes. In this study, a numerical model for an unanchored vertical vaulted-type tank was established by ANSYS software, including the tank-liquid coupling, nonlinear uplift and slip effect between the tank bottom and foundation. Four actual earthquakes recorded at different soil sites were selected as input to study the dynamic characteristics of the tank by nonlinear time-history dynamic analysis, including the elephant-foot buckling, the liquid sloshing, the uplift and slip at the bottom. The results demonstrate that, obvious elephant-foot deformation and buckling failure occurred near the bottom of the tank wall under the seismic input of Class-I and Class-IV sites. The local buckling failure appeared at the location close to the elephant-foot because the axial compressive stress exceeded the allowable critical stress. Under the seismic input of Class-IV site, significant nonlinear uplift and slip occurred at the tank bottom. Large amplitude vertical sloshing with a long period occurred on the free surface of the liquid under the seismic wave record at Class-III site. The seismic properties of the storage tank were affected by site class and should be considered in the seismic design of large tanks. Effective measures should be taken to reduce the seismic response of storage tanks, and ensure the safety of tanks.

• Computers and Concrete
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• 제4권5호
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• pp.347-362
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• 2007

Due to heterogeneities at all scales, concrete exhibits significant variability in mechanical behavior from sample to sample. An understanding of the fundamental mechanical performance of concrete must therefore be embedded in a stochastic framework. The current work attempts to address the connection between a two-dimensional concrete mesostructure and the random local material properties associated within that mesostructure. This work builds on previous work that has focused on the random configuration of concrete mesostructures. This was accomplished by developing an understanding of the effects of variations in the mortar strength and the mortar-aggregate interfacial strength in given deterministic mesostructural configurations. The results are assessed through direct tension tests that are validated by comparing experimental results of two different, pre-arranged mesostructures, with the intent of isolating the effect of local variations in strength. Agreement is shown both in mechanical property values as well as the qualitative nature of crack initiation and propagation.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1998년도 특별강연 및 추계학술발표 개요집
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• pp.11-24
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• 1998

The invention of fusion wilding technology has brought on a revolutionary change in manufacturing industry which enables the construction of large scale high temperature plants in chemical, petrochemical and power generation industries. However, among the failure cases of high temperature components, premature failures of weldments have taken a large percentage that indicates the detrimental effect of welding on structural integrity. The accurate prediction of the high temperature behaviour of welded components is thus becoming increasingly important in order to realise an optimised design and maintenance of a plant life. In the present paper, recent research activities on high temperature behaviour of welded structures are briefly summarised. A local deformation measuring technique is proposed to determine the creep properties of weldment constituents. A damage mechanics approach is introduced to study the life reduction and ductility reduction due to the presence of a weld in high temperature structures. Finally, the high temperature creep crack growth in weldments is discussed.