• Journal of Korean Society of Steel Construction
• /
• v.13 no.3
• /
• pp.313-325
• /
• 2001

Tubular bridge rail was developed to restrain and redirect a 14ton van-type truck. The developed bridge rail permits better visibility than concrete safety-shape bridge rail, and it has better structural adequacy than the existing steel and aluminum bridge rails in Korea. The new bridge rail consists of a tubular thrie beam(TTB) rail and a steel guard rail, which are connected to composite posts. The TTB shape provides both better containment of diverse bumper heights and more tight fit between the ends of bridge rail and roadside guardrails than the existing bridge rail sections currently used in Korea. Making composite post by filling concrete inside the steel pipe of the same size as are used for the roadside guardrail post was found to be more efficient in increasing the stiffness and ultimate strength than simply increasing the size of the steel pipe. The system was crash-tested for the impact condition of 14ton-80km/h-$15^{\circ}$, and it satisfied all evaluation criteria set forth in NCHRP Report 350 for a Test Level 4 safety appurtenance. Acceptable performances were obtained in computer simulations for the impact condition of S2.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.38 no.5
• /
• pp.74-84
• /
• 1996

Dynamic loading of structures often causes excursions of stresses well into the inelastic range and the influence of geometric changes on the dynamic response is also significant in many cases. Therefore, both material and geometric nonlinearity effects should be considered in case that a dynamic load acts on the structure. For developing a program to analyze the dynamic response of an axisymmetric shell in this study, the material nonlinearity effect on the dynamic response was formulated by the elasto-viscoplastic model highly corresponding to the real behavior of the material. Also, the geometrically nonlinear behavior is taken into account using a total Lagrangian coordinate system, and the equilibrium equation of motion was numerically solved by a central difference scheme. A complete finite element program has been developed and the results obtained by it are compared with those in the references 1 and 2. The results are in good agreement with each other. As a case study of its application, the developed program was applied to a dynamic response analysis of a nuclear reinforced concrete containment structure. The results obtained from the' numerical examples are summarized as follows : 1. The dynamic magnification factor of the displacement and the stress were unrelated with the concrete strength. 2. As shown by the results that the displacement dynamic magnification factor were form 1.7 to 2.3 and the stress dynamic magnification factor from 1.8 to 2.5, the dynamic magnification factor of stress were larger than that of displacement. 3. The dynamic magnification factor of stress on the exterior surface was larger than that on the interior surface of the structure.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.5 no.4
• /
• pp.580-597
• /
• 2013

Three materials SUS304, 9% Ni steel and Al 5083-O alloy, which are considered possible candidate for International Maritime Organization (IMO) type B Cargo Containment System, were studied. Monotonic tensile, fatigue, fatigue crack growth rate and Crack Tip Opening Displacement tests were carried out at room, intermediate low ($-100^{\circ}C$) and cryogenic ($-163^{\circ}C$) temperatures. The initial yield and tensile strengths of all materials tended to increase with decreasing temperature, whereas the change in elastic modulus was not as remarkable. The largest and smallest improvement ratio of the initial yield strengths due to a temperature reduction were observed in the SUS304 and Al 5083-O alloy, respectively. The fatigue strengths of the three materials increased with decreasing temperature. The largest increase in fatigue strength was observed in the Al 5083-O alloy, whereas the 9% Ni steel sample showed the smallest increase. In the fatigue crack growth rate test, SUS304 and Al 5083-O alloy showed a decrease in the crack propagation rate, due to decrease in temperature, but no visible improvement in da/dN was observed in the case of 9% Ni steel. In the Crack Tip Opening Displacement (CTOD) test, CTOD values were converted to critical crack length for the comparison with different thickness specimens. The critical crack length tended to decrease in the case of SUS304 and increase for the Al 5083-O alloy with decreasing temperature. In case of 9% Ni steel, change of critical crack length was not observed due to temperature decrease. In addition, the changing material properties according to the temperature of the LNG tank were analyzed according to the international code for the construction and equipment of ships carrying liquefied gases in bulk (IGC code) and the rules of classifications.

• Safety and Health at Work
• /
• v.11 no.3
• /
• pp.275-283
• /
• 2020

Background: In the absence of a vaccine or treatment, the most pragmatic strategies against an infectious disease pandemic are extensive early detection testing and social distancing. This study aimed to summarize public and workplace responses to Coronavirus Disease-19 (COVID-19) and show how the Korean system has operated during the COVID-19 pandemic. Method: Daily briefings from the Korean Center for Disease Control and the Central Disaster Management Headquarters were assembled from January 20 to May 15, 2020. Results: By May 15, 2020, 11,018 COVID-19 cases were identified, of which 15.7% occurred in workplaces such as health-care facilities, call centers, sports clubs, coin karaoke, and nightlife destinations. When the first confirmed case was diagnosed, the Korean Center for Disease Control and Central Disaster Management Headquarters responded quickly, emphasizing early detection with numerous tests and a social distancing policy. This slowed the spread of infection without intensive containment, shut down, or mitigation interventions. After entering the public health blue alert level, a business continuity plan was distributed. After entering the orange level, the Ministry of Employment and Labor developed workplace guidelines for COVID-19 consisting of social distancing, flexible working schedules, early identification of workers with suspected infections, and disinfection of workplaces. Owing to the intensive workplace social distancing policy, workplaces remained safe with only small sporadic group infections. Conclusion: The workplace social distancing policy with timely implementation of specific guidelines was a key to preventing a large outbreak of COVID-19 in Korean workplaces. However, sporadic incidents of COVID-19 are still ongoing, and risk assessment in vulnerable workplaces should be continued.

• Journal of agricultural medicine and community health
• /
• v.16 no.2
• /
• pp.179-194
• /
• 1991

Despite its universal coverage of health insurance, the rural health insurance program(RHIP) stands at the crossroads in Korea. The RHIP has weaknesses in stability of financing, problems of inequities in the provision of health services and has suffered from high cost of running the program. The author has analyzed these problems from the perspective of health insurance policy and presented several options for improvement. First of all, this study urged the importance of a firm Governmental commitment of RHIP with the 50% subsidization of contributions as the Government had promised, instead of the current 40%. This can be justified from the 20% subsidization by the Government for the contributions of private school teachers and their dependents, who belong to richer segments of the population. Second, various cost containment measures ought to be sought curbing the rising demand for medical through strengthening health education and increasing individual responsibility, and tightening the claim review process. Third, this study requires the Government to run a demonstration project on the introduction of case payment system for primary health care. Fourth introducing an income-related cost sharing scheme is another possibility. Reforming the cost sharing formula for large medical expenditures is recommendable for a beginning. This measure can take the form of tax credit for medical expenditures of the poor. Fifth, the degree of financial adjustment among health insurance plans should be levelled up for enhancing stability of RHIP and social solidarity. Sixth, health policy should be redirected toward development of rural health resources and higher priority should be put on relieving difficulties in access to care. Seventh. the insurance plan owned-hospital needs to be developed or provision of health services in the medically underserved areas, and the need of such facilities is particularly acute for geriatric care, rehabilitation and renal dialysis, etc. Eighth, more generous insurance benefits are required of the elderly who are suffering the most : elimination of the maximum 180 days of benefit period and provision of glasses and artificial dentures, etc. Ninth. the economies of scale principle is working for the operating expenses of regional self-employed insurance plan. Thus, measures should be instituted to pursue an optimum size of health insurance plans. Lastly, excessive dependence on exclusion items is an evil so that some radical remedies are urgently required to cut them.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.4
• /
• pp.355-361
• /
• 2014

Steam explosions can be caused by fuel-coolant interactions resulting from failure of the external vessel cooling system in a new nuclear power plant. This can threaten the integrity of structures, including the nuclear reactor and the containment building. In the present study, an improved technique for analyzing the steam explosion phenomenon was proposed on the basis of previous research and was verified by simulations involving alumina experiments. Also, the improved analysis technique was applied to determine the pressure history of the reactor cavity in accordance with postulated failure locations. The results of the analysis revealed that the effects of vessel side failure are more serious than those of vessel bottom failure, with approximately 70% higher maximum pressure.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.41 no.2
• /
• pp.140-149
• /
• 2008

This study evaluated the efficiency of an oil fence and spreading devices for one vessel in a towing tank. A series of model experiments and numerical calculations were conducted using an existing oil fence for two vessels and a new method for one vessel. Models of the oil fence and spreading devices were constructed on $1/20^{th}$ scale from waterproofed nylon fabric and canvas. The tensions acting on the model of the oil fences and the horizontal distance between the spreading devices were calculated numerically while the oil fences were being towed. The results were extremely close to the results of the model experiments. The ratio of the opening width to the total length of the oil fence, which shows the efficiency of the oil fence for one vessel, was 49.7% in 0.4 m/sec. Therefore, the proposed oil fence system should be very useful for oil containment at sea. As the opening width of the oil fence is not proportional to the length of the towing rope, it may be reasonable to maintain the towing rope at approximately 100 m. Furthermore, a reasonable towing speed, when operating the oil fence for one vessel equipped with spreading devices, was within 0.4 m/sec.

• Nuclear Engineering and Technology
• /
• v.45 no.5
• /
• pp.625-636
• /
• 2013

Pressing demands of economic competitiveness, the need for large-scale deployment, minimizing the need of human intervention, and experience from the past events and incidents at operating reactors have guided the evolution and innovations in reactor technologies. Indian innovative reactor 'AHWR' is a pressure-tube type natural circulation based boiling water reactor that is designed to meet such requirements, which essentially reflect the needs of next generation reactors. The reactor employs various passive features to prevent and mitigate accidental conditions, like a slightly negative void reactivity coefficient, passive poison injection to scram the reactor in event of failure of the wired shutdown systems, a large elevated pool of water as a heat sink inside the containment, passive decay heat removal based on natural circulation and passive valves, passive ECC injection, etc. It is designed to meet the fundamental safety requirements of safe shutdown, safe decay heat removal and confinement of activity with no impact in public domain, and hence, no need for emergency planning under all conceivable scenarios. This paper examines the role of the various passive safety systems in prevention and mitigation of severe plant conditions that may arise in event of multiple failures. For the purpose of demonstration of the effectiveness of its passive features, postulated scenarios on the lines of three major severe accidents in the history of nuclear power reactors are considered, namely; the Three Mile Island (TMI), Chernobyl and Fukushima accidents. Severe plant conditions along the lines of these scenarios are postulated to the extent conceivable in the reactor under consideration and analyzed using best estimate system thermal-hydraulics code RELAP5/Mod3.2. It is found that the various passive systems incorporated enable the reactor to tolerate the postulated accident conditions without causing severe plant conditions and core degradation.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.26 no.5
• /
• pp.327-333
• /
• 2013

The purpose of this study is to predict sloshing pressure of a actual tank by using measured pressure in scaled down tank and to evaluate with structural strength of LNG Corner Block. For this purpose, we performed sloshing analysis about 138K class tank by using Ansys CFX program, and were measured both average pressure and maximum peak pressure according to scaled tank ratio. Also, measured pressure was converted to pressure of the actual tank by Froude scale law, and we conducted the evaluation of structural strength about the conner block of actual size KC-1.

• Nuclear Engineering and Technology
• /
• v.26 no.2
• /
• pp.168-178
• /
• 1994

Accident Management involves all measures to prevent core damage and retain the core within the reactor vessel, maintain containment integrity and minimize off-site releases. The accident management approach includes : (1) advanced evaluation of candidate strategies, (2) development of procedures to execute appropriate actions efficiently, and (3) identification and provision for materials, tools, and possible modifications to the plant system that may be needed for such execution. When assessing accident management strategies it effectiveness, adverse effect and its feasibility, including information needs and compatibility with existing procedures, must be considered. The objective of this paper is to introduce analytical tools of decision trees and influence diagrams to develop a framework for modeling and assessing severe accident management strategies. The characteristics associated with these took are presented. Based on decision trees and influence diagrams, the framework is applied to a simple example associated with a single decision.