• 한국해안해양공학회지
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• 제19권2호
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• pp.113-127
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• 2007

본 연구에서는 직립 방파제 케이슨의 활동에 따른 복구비용, 과도한 케이슨 활동 발생시 항만 폐쇄에 따른 경제적 피해 비용 그리고 월파에 의한 일시적 작업 중단에 따른 경제적 피해 비용을 동시에 고려하는 기대 총 건설비 산정 모델을 수립하였다. 발생시점이 서로 다른 피해 비용을 일정한 기준으로 산정하기 위해 할인율을 적용하였다. 케이슨의 최적 단면은 방파제 수명 동안의 기대 활동량의 허용범위 내에서 기대 총 건설비용이 최소가 되는 단면으로 정의되며, 그 기대 활동량의 허용치는 0.3 m와 0.1 m 두 가지 경우에 대해 살펴보았다. 과도한 케이슨 활동에 의한 항만 폐쇄에 따른 경제적 피해 비용과 그 산정 기준이 케이슨 복구비용이나 월파에 의한 작업 중단에 따른 경제적 피해 비용보다 최적 단면 결정에 더 중요한 요인임을 확인하였고, 항만 폐쇄에 대한 케이슨 활동량의 임계 칼이 커질수록 케이슨의 최적 단면은 기대 총 건설비의 최소점보다 기대 활동량의 허용치에 의해 결정되는 것으로 나타났다.

• 대한토목학회논문집
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• 제37권1호
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• pp.61-72
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• 2017

자연재난에 따른 인명 및 재산피해의 증가로 재난 예방 및 대응에 대한 관심이 증가하고 있다. 우리나라에서도 1994년에서 2013년까지 지난 20년간 자연재해에 의한 피해액은 약 12조 원 중 대설에 의한 피해가 약 13%로 대설도 강우나 태풍보다는 작은 규모이나, 의미 있는 규모의 피해를 야기하고 있다는 것을 알 수 있다. 그러므로 본 연구에서는 대설피해액 추정을 위해 강원지역을 대상으로 기후관련 요인(최심적설량, 평균습도, 최저기온), 사회 경제적 요인(농촌지역인구밀도, 지역총생산량)을 독립변수로 하는 동시입력방식의 다중회귀모형을 구축하였다. 적용결과, 극한 값들에 대한 설명력이 다소 낮기는 하지만, 수정결정계수가 0.7 이상인 경우도 다수 존재하는 등 대설 발생 시 신속한 재난 대응에 활용하기에는 적용성이 충분하다고 판단된다.

• Smart Structures and Systems
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• 제17권6호
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• pp.957-980
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• 2016

Structural damage detection (SDD) is a challenging task in the field of structural health monitoring (SHM). As an exploring attempt to the SDD problem, a hybrid self-adaptive Firefly-Nelder-Mead (SA-FNM) algorithm is proposed for the SDD problem in this study. First of all, the basic principle of firefly algorithm (FA) is introduced. The Nelder-Mead (NM) algorithm is incorporated into FA for improving the local searching ability. A new strategy for exchanging the information in the firefly group is introduced into the SA-FNM for reducing the computation cost. A random walk strategy for the best firefly and a self-adaptive control strategy of three key parameters, such as light absorption, randomization parameter and critical distance, are proposed for preferably balancing the exploitation and exploration ability of the SA-FNM. The computing performance of the SA-FNM is evaluated and compared with the basic FA by three benchmark functions. Secondly, the SDD problem is mathematically converted into a constrained optimization problem, which is then hopefully solved by the SA-FNM algorithm. A multi-step method is proposed for finding the minimum fitness with a big probability. In order to assess the accuracy and the feasibility of the proposed method, a two-storey rigid frame structure without considering the finite element model (FEM) error and a steel beam with considering the model error are taken examples for numerical simulations. Finally, a series of experimental studies on damage detection of a steel beam with four damage patterns are performed in laboratory. The illustrated results show that the proposed method can accurately identify the structural damage. Some valuable conclusions are made and related issues are discussed as well.

• Steel and Composite Structures
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• 제10권6호
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• pp.475-487
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• 2010

Most of steel structures in various industries are subjected to corrosion due to environmental exposure. Corrosion damage is a serious problem for these structures which may reduce their carrying capacity. These aging structures require maintenance and in many cases, replacement. The goal of this research is to consider the effects of corrosion by developing a model that estimates corrosion loss as a function of exposure time. The model is formulated based on average measured thickness data collected from three severely corroded I-beams (nearly 30 years old). Since corrosion is a time-dependent parameter. Analyses were performed to calculate the lateral buckling capacity of steel beam in terms of exposure time. Minimum curves have been developed for assessment of the remaining lateral buckling capacity of ordinary I-beams based on the loss of thicknesses in terms of exposure time. These minimum curves can be used by practicing engineers for better estimates on the service life of corrosion damaged steel beams.

• 대한기계학회논문집A
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• 제25권4호
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• pp.629-636
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• 2001

In order to investigate the possibility of impact punching in brittle materials, an experimental setup was developed. In the setup, a long bar as a punch was used to apply the impact load to the specimen plate and measure the applied impact force during the impact punching process. Impact punching tests with various shape of punches were performed in soda-lime glass and silicon wafer under a different level of contact pressure. The damage appearance after the impact punching was examined according to the applied contact pressure. The minimum contact pressure required for a complete punching in glass specimens without development of radial cracks around the punched hole was sought at each condition. The minimum contact pressure increased with increasing the thickness of specimens and decreasing the end radius of punches. The profile of impact forces was measured during the impact punching experiment, and it could explain well the behavior of the punching process in brittle material plates. The measured impact force increased with increasing the contact pressure applied to the plates.

• 한국생산제조학회지
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• 제20권5호
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• pp.528-534
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• 2011

This study analyzes thermal stress and durability fatigue on the modelling of EGR valve. In case of 10% opening at its inlet, the minimum temperature gets cool as 3 times as inlet temperature. The maximum equivalent stress becomes lowest as the value of $2.6274{\times}109$ Pa and fatigue life becomes highest as 23.657 Cycle. But the minimum temperature gets cool as 2.2 times as inlet temperature in case of 50% opening at its inlet. The equivalent stress becomes higher and fatigue life becomes lower than in case of 10% opening. In case of 100% opening at its inlet, the minimum temperature gets cool as 0.2 times as inlet temperature. The equivalent stress becomes lower and fatigue life becomes higher than in case of 50% opening. Maximum equivalent stress and total deformation are shown at the closing of EGR valve by the pressure of inflow gas. The structural analysis result of this study can be effectively utilized with the design of EGR valve by investigating prevention and durability against its damage.

• 한국실내디자인학회논문집
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• 제15권2호
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• pp.174-182
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• 2006

This study is focused on interior materials and wastes among other diverse environmental strategies for sustainable construction. The case study was carried out by using MSDG, mainly utilized in evaluating performance of sustainable constructions in Minnesota, the US, as an evaluation tool, in order to analyze American practices. In this study, a field inspection was conducted to 6 Minnesota cases, following a preliminary examination through literature study and portal site search, and then, constructive reports, interviews with people in charge, and empirical data including photos were added to the basic data provided by MSDG and MOEA As a result, it turned out *that sustainable materials were mainly used even in newly constructed buildings and wastes were properly managed in an environment-friendly, economical, and ethical manner, *that life cycle assessment showed reduction in some constructive costs even when the basic costs were high, *that some recycled finish materials were widely used in diverse areas, *that minimum consumption of raw materials, minimum environmental damage by materials, minimum effect of materials on IAQ were found in the examined cases, and *that many attempts were made to minimize resource consumption and constructive wastes from diverse perspectives.