• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.259-272
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• 2019

Steel-concrete single-leaf blast-resistant doors are protective structures consisting of a steel box and reinforced concrete slab. By the domestic blast-resistant doors, the structure is not designed efficiently because few studies have examined the effects of variables, such as the blast pressure, rebar ratio, and steel plate thickness on the structural behavior. In this study, the structural behavior of the doors was analyzed using the FE method, and the support rotation and ductility ratio used to classify the structural performance were reviewed. The results showed that the deflection changes more significantly when the plate thickness increases than when the rebar spacing is a variable. This is because the strain energy absorbed by the door is reduced considerably when the plate thickness increases, and as a result, the maximum deflection becomes smaller. According to a comparison of the calculated values of the support rotation and the ductility ratio, the structural performance of the doors could be classified based on the support rotation of one degree and ductility ratio of three. On the other hand, more explosion tests and analytical studies will be needed to classify the damage level.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.339-349
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• 2020

Double-leaf blast-resistant doors consisting of steel box and slab are application-specific structures installed at the entrances of protective facilities. In these structural systems, certain spacing is provided between the door and wall. However, variation in the boundary condition and structural behavior due to this spacing are not properly considered in the explosion analysis and design. In this study, the structural response and failure behavior based on two variables such as the spacing and blast pressure were analyzed using the finite element method. The results revealed that the two variables affected the overall structural behavior such as the maximum and permanent deflections. The degree of contact due to collision between the door and wall and the impact force applied to the door varied according to the spacing. Hence, the shear-failure behavior of the concrete slab was affected by this impact force. Doors with spacing of less than 10 mm were vulnerable to shear failure, and the case of approximately 15-mm spacing was more reasonable for increasing the flexural performance. For further study, tests and numerical research on the structural behavior are needed by considering other variables such as specifications of the structural members and details of the slab shear design.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.287-296
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• 2019

In this study, the effect of ground boundary conditions on the evaluation of blast resistance performance of precast arch structures was evaluated by a numerical analysis method. Two types of boundary conditions, namely, fixed boundary conditions and a perfectly matched layer (PML) were applied to numerical models. Blast loads that were much higher than the design load of the target structure were applied to compare the effects of the boundary conditions. The distribution and path of the ground explosion pressure, structural displacement, fracture of concrete, stress of concrete, and reinforcing bars were compared according to the ground boundary condition settings. As a result, the reflecting pressure shock wave at the ground boundaries could be effectively eliminated using PML elements; furthermore, the displacement of the foundation was reduced. However, no distinct difference could be observed in the overall structural behavior including the fracture and stress of the concrete and rebar. Therefore, when blast simulations are performed in the design of protective structures, it is rational to apply the fixed boundary condition on the ground boundaries as conservative design results can be achieved with relatively short computation times.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.1
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• pp.136-142
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• 2008

Recently, cabled-suspension bridges and suspension bridge have been increasingly built in korea. But such structures were often damaged by fire due to car collison. In this study, the cabled-suspension bridges constructed under the kind of the project of national road aggrandizement are modeled using Solid Works 2007. The COSMOS FloWorks 2007 software are used for Heat Transfer Analysis and Thermal Stress Analysis. The safety of wire, HDPE pipe and stainless steel pipe are investigated. The major variables for the analysis are the temperature of the heat source, the distance between the fire-proof bulk head and the heat source, wind velocity, and the height of the end of Stainless steel pipe.

• Journal of Global Scholars of Marketing Science
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• v.15 no.1
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• pp.1-20
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• 2005

The object of this study is to explore factors affecting customer satisfaction and customer loyalty of instant messenger service. We propose that service qualities (tangibility, assurance, responsiveness, empathy, reliability) affect customer satisfaction of instant messenger service, customer satisfactions do customer loyalty. As moderating factors of the relationship between customer satisfaction and customer loyalty, switching costs are suggested. To accomplish the object of this study data are collected from instant messenger user by survey research. We analyse the research model using structural equation model and moderated multiple regression. The result are as follows: (1) tangibility and responsiveness affect customer satisfaction. (2) customer satisfaction affects customer loyalty. (3) switching costs moderated the relationship between customer satisfaction and customer loyalty.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.351-351
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• 2015

음극방식법은 피방식체에 외부전원을 인가하거나 보다 활성 금속을 전기적으로 연결하여 피방식체를 일정 전위까지 음극분극 되도록 하여 부식을 억제하는 방법이다. 해수 중 음극방식을 실시할 경우 생성되는 석회질 피막(Calcareous deposit)은 소요전류밀도 감소로 인한 희생양극의 수명연장 및 물리적 방호벽 역할을 한다. 그러나 일반적인 석회질 피막은 세라믹과 같은 화합물로써 밀착력이 매우 약하며, 적지 않은 피막 형성 시간이 소요된다. 따라서 본 연구에서는 해수 중 음극전류 프로세스를 응용하여 실제 강관의 해중부 및 간만대 영역까지 석회질 피막을 균일-치밀하게 형성시키기 위한 최적의 조건을 찾고자 하였다. 각 조건별로 제작된 석회질 피막은 SEM, EDS 및 XRD를 통해 막의 모폴로지, 조성원소 및 결정 구조를 분석하였으며, 이를 바탕으로 희생양극 종류(Al, Zn) 및 1, 3, $5mA/m^2$의 전류밀도 조건에서 부위-기간별 형성된 석회질 피막의 메커니즘을 해명하였다. 또한 밀착성과 내식특성을 평가하기 위해 테이핑 테스트, 침지-자연전위 거동을 분석 및 평가하였다.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.1
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• pp.29-38
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• 2022

In offshore installations, fires cause the structure to lose its rigidity and it leads to structural integrity and stability problems. The Passive Fire Protection (PFP) system slows the transfer rate of fire heat and helps prevent the collapse of structures and fatality. Especially, intumescent epoxy coating is widely used in the offshore industry, and not only is the material cost expensive, but it also takes a lot of time and cost for construction. Several studies have been conducted on the efficient application and optimal design of the PFP system. However, the mechanical properties and the strength of the PFP material have not been considered. In addition, researches on the correlation between the thickness of PFP and the structural behavior were insufficient. Therefore, this study aims to analyze the thermal and mechanical effects of the PFP on the structure when it is applied to the structural member. In particular, it is intended to resolve the change in strength characteristics of the structural members as the thickness of the PFP increases.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.2
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• pp.12-28
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• 2019

Road geometry is one of the many factors that cause crashes, but the effect on traffic accident depends on weather conditions even under the same road geometry. This study identifies the variables affecting the crash severity by matching the highway accident data and weather data for 14 years from 2001 to 2014. A hierarchical ordered Logit model is used to reflect the effects of road geometry and weather condition interactions on crash severity, as well as the correlation between individual crashes in a region. Among the hierarchical models, we apply a random intercept model including interaction variables between road geometry and weather condition and a random coefficient model including regional weather characteristics as upper-level variables. As a result, it is confirmed that the effects of toll, ramp, downhill slope of 3% or more, and concrete barrier on the crash severity vary depending on weather conditions. It also shows that the combined effects of road geometry and weather conditions may not be linear depending on rainfall or snowfall levels. Finally, we suggest safety improvement measures based on the results of this study, which are expected to reduce the severity of traffic accidents in the future.

• Journal of Energy Engineering
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• v.21 no.4
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• pp.339-345
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• 2012

RMembrane LNG storage tanks have been recently investigated to replace full-containment LNG storage tanks because of safety and cost aspects. Quantitative Risk Analysis (QRA) and Finite Element Method (FEM) were used to evaluate safety of membrane LNG storage tanks. In this study, structural safety evaluation results via FEM analysis showed that both membrane type and full-containment type cryogenic LNG storage tanks with 140,000 $m^3$ capacity were equivalently safe in terms of strength safety and leakage safety of a storage tank system. Also, Fault Tree Analysis (FTA) was used to improve the safety of membrane LNG storage tanks and membrane LNG tanks were modified by adding three safety equipments: impact absorber structure for the low part of the membrane, the secondary barrier to diminish the thermal stress of the corner part of the outer tank, and a pump catcher in case of falling of a pump. Consequently, the safety of the modified membrane LNG storage tanks were proved to be equivalent to that of full-containment LNG storage tanks.

• Journal of the Korean Society of Radiology
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• v.9 no.7
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• pp.433-438
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• 2015

To evaluate the radiation exposure level based on radiation workers' locations in dental radiography, the radiation dose rate in the radiographic room, lead glass, and operation system was measured. To that end, various devices were used, such as a Standard(Max-GLS, Shinhung), a panorama (PCH-2500, Vatech), a cephalometric radiography (PCH-2500), and a cone beam CT (PHT-30LFO, Vatech), as well as a PM1405 equipment as a radiation meter. Radiography conditions were set the same as the factors used in the clinical setting. As the result, the cone beam CT turned out the highest with 98 uSv and the standard showed the lowest level with 0.4 uSv/h. The panorama was measured to be higher than the Cephalo due to its different focus mode. On the lead glass surface and in the operation stand, the oral radiography device, panoramic, and Cephalo all were measured below the recording level. However, the cone beam CT was measured to have the leakage dose. Thus, radiation involved workers should be equipped with appropriate protection tools and reduce radiography time as much as possible. In addition, the structure of the radiation chamber should be also designed efficiently. Dental radiography has continued to grow in recent years, so it is necessary take appropriate protection measures for patients and radiation workers.