• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2A
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• pp.115-120
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• 2011

The strength of reinforced concrete members has uncertainty from material properties of, concrete and reinforcements, section dimensions, and construction errors and so on. The accurate evaluation of these uncertainties is necessary to assure the reasonable safety. The uncertainties should be taken into account in design using structural reliability theory which requires probabilistic models for such uncertainties. In current Korean design code, most reliability evaluations were performed based on foreign data because of lack of local data. In this paper, the probabilistic models for yield strength of reinforcements were developed based on local data. The effects of various factors, nominal yield strength, diameter of reinforcements, and companies, on the models are also examined. According to data analysed, the effects of those factors are not significant. The probability model for yield strength of reinforcements in Korea can be expressed with Beta distribution based on collected data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.389-394
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• 2017

In a conventional ship structure, stiffeners with an asymmetric section, such as inverted angles, are used widely despite the disadvantage of strength compared to the stiffeners with a symmetric section, such as a built-up T. On the other hand, T-type built-up members are attracting more attention than L-type inverted angles due to the increased size of ships. The purpose of this study was to develop an optimal design program for a built-up T, and apply an evolution strategy as an optimization technique. In the optimization process, the gross thickness concept was adopted for the design variables and objective function, and the constraints are set up based on HCSR (Harmonized Common Structural Rules). Using the developed program in this study, the optimal stiffener design was carried out for 300K VLCC and 158K COT of which the orders were obtained lately. The optimal results revealed the weight reduction effect of 144 tons and 60 tons, respectively.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.97-105
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• 1996

For the minimum weight design of ship structures it is desirable that tank arrangement is predetermined to obtain the minimum weight and then structural arrangement and scanting of each murder is determined to obtain the minimum weight within the given tank arrangement. To carry out the tank arrangement to give minimum weight a minimum weight design program which covers whole ship structures is developed by the combination of minimum weight design program of longitudinal members by classification rules and minimum weight design program of transverse members by generalized slope deflection method which were developed by the authors. The hullweight is estimated by summation of the weight of cargo hold part and the weight except cargo hold part which can be estimated by the empirical formula. In this study, the variation of hullweight is shown with the number of tank, the number of web and the location of longitudinal bulkhead. For the application of actual design alternative designs of tank arrangement which satisfy MARPOL regulation are determined. And several minimum weight designs of whole ship structures are carried out to obtain the tank arrangement which gives minimum weight and then the hullweight is compared with that of existing ship.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.5
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• pp.71-81
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• 2007

For the design of composite bridge piers, detail requirements for the reinforcements is not clear to satisfy the required seismic performance. Composite bridge piers were suggested to reduce the sectional dimensions and to enhance the ductility of the columns under earthquake loadings. In this paper, five specimens of concrete encased composite columns of 400mm diameter with single core steel were fabricated to investigate the seismic performance of the composite columns. Shaking table tests and a Pseudo-Dynamic test were carried out and structural behavior of small-scaled models considering near-fault motions was evaluated. Test parameters were the pace of the transverse reinforcement, lap splice of longitudinal reinforcement and encased steel member sections. The displacement ductility from shaking table tests was lower than that from the pseudo-dynamic test. Limited ductile design and 50% lap splice of longitudinal reinforcement reduced the displacement ductility. Steel ratio showed significant effect on the ultimate strength. Lap splice and low transverse reinforcements reduced the displacement capacity. The energy dissipation capacity of composite columns did not show significant difference according to details.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.4
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• pp.137-146
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• 1999

Inspection becomes to be important in the safety of structure and economical viewpoint, because structural damage accompanies lots of economical cost and social problems. Especially ship structure is composed of a lot of members and it is impossible to inspect all members continuously. The purpose of this paper is to get optimal inspection plan containing inspection time and method. Crack is one of major modes on the structural failure and can lead to collapse of structure. In this paper, the deteriorating process, which contains inspection to detect the crack before the propagation to large crack, is idealized as Markov chain model. Genetic algorithm is also used to accomplish the optimization of inspection plan. Especially, the probabilistic characteristics of cracks are changed, because ship is operating in corrosive environments and the scantling of structural members is reduced due to corrosion. Non-stationary Markov chain model is used to represent the process of corrosion in structural members. In this paper, the characteristics of indivisual inspection plan are compared by numerical examples for the change of corrosion rate, the cost due to scheduled system down and target failure probability. From the numerical example, it can be seen that the improvement of fatigue life for the members with short fatigue life is the most effective way in order to reduce total maintenance cost.

• Magazine of the Korea Concrete Institute
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• v.4 no.3
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• pp.123-134
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• 1992

본연구는 실물크기의 프리캐스트 콘크리트 판구조물의 부분구조체를 모형화하여 실험한 결과를 분석한 것이다. 구조물의 역학적 특성과 파괴성상을 파악하기 위한 구조실험은 실물크기의 구조물과 부재로써 실시하는 것이 가장 좋은 방법이지만, 이것은 치수가 크므로 공간적으로 제한을 받고 많은 시간과 비용을 필요로 하기 때문에 모형실험을 이용하게 된다. 이러한 모형실험을 최소한의 오차범위내에서 원형실험과 같은 재현하고 예측하도록 실험을 준비하는 데에는 상사법칙이 필요하게 된다. 모형은 무엇보다도 원형과의 응력-변형도 관계 등 구성재료에 대한 상사요구조건을 만족시키는 것이 중요하지만, 본 연구의 대상은 1/3축척으로써 기하학적인 요소와 사용재료에 대한 강도의 상사성만을 고려한 모형이다. 본 연구에서는 이러한 모형구조물의 거동을 원형실험결과와 비교하여 상사성 확보의 문제와 가능성을 조사하였다.

• 한국공간정보시스템학회:학술대회논문집
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• 2005.11a
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• pp.217-224
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• 2005

하천정보의 관리기관이 다양하고 정보의 표현 및 분석단위가 관리주체에 따라 다르며, 하천정보의 체계적이고 종합적인 정책자료 분석 제공 기능의 부재로 인한 이수 및 치수, 하천 환경 등을 고려한 국가수자원종합계획의 수립을 어렵게 해왔다. 하천 및 유역정보의 관리단위를 일원화하여 국가적으로 표준화시키고, 유역정보, 수문정보 등에 대해서 국가 수자원 정보망의 형성을 통해서 하천정보의 유기적인 공동이용을 추구해야 한다. 또한, 정보시스템 구축에 있어서 시스템간 중복을 방지하고 상호 연계가 원활히 이루어져 대정부, 대국민에 대한 종합적인 정보 제공이 가능하도록 추진을 할 필요가 있다. 본 연구에서는 하천정보 신뢰성 높고 다양한 하천정보 DB 구축을 통하여 보다 편리하고 유용한 시스템 사용 환경을 제공 및 지원하기 위한 방안을 제시하고자 하였다. 이를 위해 국내외 하천정보서비스 구축사례를 분석하고 국내 실정에 맞는 하천정보서비스의 구축방안을 제시하였으며, 이를 위해서는 지속적인 중장기종합정보화전략계획 수립과 국내에 적합한 필수 데이터 항목도출, 데이터모델과 구축방법론 표준화로 체계적인 유지관리가 가능하도록 하여야 할 것이다. 또한 하천공간정보의 유통체계는 기존의 국가공간정보 유통 기구를 이용하는 것이 합리적인 것으로 사료된다.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.2
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• pp.19-25
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• 2001

Structural design requirements for very large floating structures(VLFS) are different corresponding to this purpose and structural type. In this study, the structural design procedure of VLFS is described, composing of the following processes : construction of design conditions. choice of structural types and main materials, estimation of structural design loads, determination of structural arrangements, and scantling of structural members. As an example of practical application, the initial structural design of floating airport and container terminal for Pusan is demonstrated.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.07a
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• pp.469-477
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• 2003

삼림에서 벌채된 목재는 대부분 건조공정을 거쳐 산업용 재료가 되므로 건조정도에 따라 목질 재료의 품질이 결정된다. 목재에 포함된 과도한 수분을 제거하여 운송비용을 줄일 수 있으며 목재를 적절하게 건조하게 되면 목재 사용 중에 발생할 수 있는 수축 및 팽윤을 제한할 수 있을 뿐만 아니라 건조과정을 통해 비틀림, 갈라짐, 할열 등과 같은 결함의 발생을 크게 줄일 수 있다. 또한 건조된 목재는 생재에 비해 기계 가공이 보다 용이하기 때문에 정확한 치수로 재단이 가능하며, 각각의 부품으로 재단한 부재를 못이나 나사못, 볼트, 접착제 등을 사용하여 견고하게 짜 맞출 수 있다. 그리고 도장성능이 향상되어 기능성을 증진시킬 수 있으며, 건조 후의 방부처리를 통해 장기간의 사용이 가능하다. (중략)

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.5-6
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• 2009

In this study, with 2% of total PVA fiber volume fraction identically, flexural performances of ECC had long and short fibers were assessed. In the material tests, flexural properties of a mixture with 1.6% REC15 and 0.4% RF4000 were most superior. Quasi-static and dynamic tests with six 160${\times}$290${\times}$2300 mm specimens were carried out, and improvement of shear strength and performance of partial placing of ECC were estimated.