• Structural Engineering and Mechanics
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• v.62 no.4
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• pp.455-464
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• 2017

Rayleigh damping model is recommended in the recently developed Performance-Based Earthquake Engineering (PBEE) methodology, but this methodology does not provide sufficient information due to the complexity of the damping mechanism. Furthermore, each Rayleigh-type damping model may have its individual limitations. In this study, Rayleigh-type damping models that are used widely in engineering practice are discussed. The seismic performance of a large-span single-layer latticed dome subjected to earthquake ground motions is investigated using different Rayleigh damping models. Herein a simulation technique is developed considering low cycle fatigue (LCF) in steel material. In the simulation technique, Ramberg-Osgood steel material model with the low cycle fatigue effect is used to simulate the non-uniformly distributed material damping and low cycle fatigue damage in the structure. Subsequently, the damping forces of the structure generated by different damping models are compared and discussed; the effects of the damping ratio and roof load on the damping forces are evaluated. Finally, the low cycle fatigue damage values in sections of members are given using these damping models. Through a comparative analysis, an appropriate Rayleigh-type damping model used for a large span single-layer latticed dome subjected to earthquake ground motions is determined in terms of the existing damping models.

• International journal of steel structures
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• v.18 no.4
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• pp.1200-1209
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• 2018

In this study, a probabilistic framework of the damage assessment of pipelines subjected to extreme hazard scenario was developed to mitigate the risk and enhance design reliability. Nonlinear 3D finite element models of T-joint systems were developed based on experimental tests with respect to leakage detection of black iron piping systems, and a damage assessment analysis of the vulnerability of their components according to nominal pipe size, coupling type, and wall thickness under seismic wave propagations was performed. The analysis results showed the 2-inch schedule 40 threaded T-joint system to be more fragile than the others with respect to the nominal pipe sizes. As for the coupling types, the data indicated that the probability of failure of the threaded T-joint coupling was significantly higher than that of the grooved type. Finally, the seismic capacity of the schedule 40 wall thickness was weaker than that of schedule 10 in the 4-inch grooved coupling, due to the difference in the prohibition of energy dissipation. Therefore, this assessment can contribute to the damage detection and financial losses due to failure of the joint piping system in a liquid pipeline, prior to the decision-making.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.103-114
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• 2013

Recently, there is a growing interest on sustainable connection system that makes it possible to reuse of main structural members by concentrating most of the damage in the frame caused by strong horizontal force, such as earthquake, to damper. In this study proposed a new type of damage-controlled connection system applying these concepts and analysed the major structural performance of the proposed system through the full-scale cyclic loading test and nonlinear finite element analyses. According to the result, it derived the optimal damper/beam strength ratio that minimize the damage of main members and satisfy at least the fully plastic moment of the beam. And it was to verify the possibility of applying as seismic connection details.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.267-277
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• 2003

The purpose of this study makes a retrofit and rehabilitation practice trough the analysis and the improvement for the underlying problem of current retrofit and rehabilitation methods. Therefore, the deterioration process, the damage cause, the condition classification, the fatigue mechanism and the applied quantity of strengthening methods for slab bridge decks were analysed. Artificial neural networks are efficient computing techniqures that are widely used to solve complex problems in many fields. In this study, a back-propagation neural network model for estimating a management on existing slab bridge decks from damage cause, damage type, and integrity assessment at the initial stsge is need. The training and testing of the network were based on a database of 36. Four different network models werw used to study the ability of the neural network to predict the desirable output of increasing degree of accuracy. The neural networks is trained by modifying the weights of the neurons in response to the errors between the actual output values and the target output value. Training was done iteratively until the average sum squared errors over all the training patterms were minimized. This generally occurred after about 5,000 cycles of training.

• Smart Structures and Systems
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• v.13 no.5
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• pp.849-868
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• 2014

An indirect approach is explored for structural health bridge monitoring allowing for wide, yet cost-effective, bridge stock coverage. The detection capability of the approach is tested in a laboratory setting for three different reversible proxy types of damage scenarios: changes in the support conditions (rotational restraint), additional damping, and an added mass at the midspan. A set of frequency features is used in conjunction with a support vector machine classifier on data measured from a passing vehicle at the wheel and suspension levels, and directly from the bridge structure for comparison. For each type of damage, four levels of severity were explored. The results show that for each damage type, the classification accuracy based on data measured from the passing vehicle is, on average, as good as or better than the classification accuracy based on data measured from the bridge. Classification accuracy showed a steady trend for low (1-1.75 m/s) and high vehicle speeds (2-2.75 m/s), with a decrease of about 7% for the latter. These results show promise towards a highly mobile structural health bridge monitoring system for wide and cost-effective bridge stock coverage.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.17 no.3
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• pp.203-214
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• 2013

Objectives Yusanghan(類傷寒) means disease which chills and fever manifest like Cold damage(傷寒) but not Cold damage. However, study on Yussanghan is insignificant. The purpose of this study is to examine the origin and development process of Yusanghan. Methods: 1. Terms and disease related with Yusanghan was collected from books covering Cold damage of all time and analyzed. 2. The transition history was researched by analyzing collected terms. 3. Total appearance frequency of all time by collected disease was researched. Results: Yusanghan was appeared in Hwalinseo(活人書), which Ju Geong(朱肱) of the Song Dynasty wrote, for the first time and the definition and type were established. For the types of those, there are four diseases such as Phlegm-Fluid Retention(痰飮), Food Accumulation(食積), Vexation of Deficiency Type(虛煩), Beriberi(脚氣). Since then, the theory about Yusanghan had developed and the number of types had also increased until the Myung Dynasty. Conclusions: In early days, External Contraction Diseases(外感病) was not included in Yusanghan, but since the late Myung Dynasty, there were a lot of doctors who included External Contraction Diseases in Yusanghan, not in Cold damage. There are Summerheat Stroke, Wind-Dampness(風濕), and Warm Disease(溫病) etc. for included External Contraction Diseases. Because of this, the number of types of Yusanhan had significantly increased.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.36 no.1
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• pp.109-119
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• 2018

The purpose of this study is to analyze the geographical location information data and the damage trends according to the type of landform for the study of various cultural properties in 44 traditional places with national designated cultural properties damaged by the racing earthquake on September 12, 2016. The landform type was the most enclosed type, and the location type was more frequent in the surrounding area, such as urban and rural areas. The waterside type was located along rivers, rivers, valleys, lakes, and oceans except for the top of the mountain, but this area was found to be vulnerable to earthquakes, It is understood that it should be referred from cultural property management the side. 26 of the total 44 were temples. The elevation and slope increased with increasing of the flat type, the background type, the enclosed type, the mountain type, and the top type. Most often located on 1-20 % slopes, with the slope facing south more often than not. Within the 10 km range from the epicenter, 23% were concentrated, within the range of nearly 65 km, the background type was closest, and was concentrated in the northeast and southwest from the epicenter. In this study, it is meaningful to analyze earthquake damage in various aspects from the viewpoint of traditional space which is a landscaping cultural property and it will be used for planning, designing and managing traditional spaces.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.1
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• pp.49-58
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• 1997

The membrane type LNG tank is non self-supporting tank which consists of both primary and secondary membrane supported through the insulation boxes by the adjacent hull struc¬ture. Although the membranes are not structural member. They are subject to periodical cyclic loads due to the thermal expansion and other expansions or contraction of membrane. At the design stage of the tank, an analytical and experimental approach on the fatigue strengths of membrane and its welds is necessary in order to assist the designer and the inpector. In this study the evaluation method of fatigue strength of membrane type LNG tank is pre¬sented with FEM analysis and fatigue test of lap welds and it contains the following:1) The fatigue tests and preparation of design S - N curve for lap welds 2) FEM analysis of test specimens 3) Estimation of cumulative damage factor of lap welds 4) Guideline for inspection of lap welds of membrane type LNG tank As the results of analytical and experimental approaches in this study, the evaluation method of fatigue strengths of membrane type LNG tank is proposed, which is expected to be useful for design and inspection of membrane type LNG tank.

• Journal of ILASS-Korea
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• v.15 no.2
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• pp.83-93
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• 2010

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feedwater heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare degree of shell wall thinning mitigation rate to squared type with mitigation rate of other type baffle plate, four different types of impingement baffle plate-squared, curved, mitigating type and multi-hole type-applied inside the shell. With these comparison data, this paper describes operation of experiments and numerical analysis which is composed similar condition with real feed water heater. And flow visualization is operated for verification of experiments and numerical analysis. In conclusion, this study shows that mitigating type and multi-hole type baffle plate are more effective than other baffle plate about prevention of pressure concentration and pressure value decrease.

• Journal of Biosystems Engineering
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• v.14 no.3
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• pp.207-214
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• 1989

In this study, impact force and angular displacement of the pendulum were measured by the load cell and potentiometer. Mechanical behavior of rough rice under impact loading was able to analyze precisely and efficiently, because measured data were accumulated and handled by the automatic data acquisition system making use of microcomputer system. Impact force and angular displacement were measured with a resolutiln of 1/1500 seconds in time. Mechanical behavior such as force and energy at rupture point of Japonica type and Indica type rough rice were measured with this system. After impact loading, the damage of rough rice was examined with the microphotograph and an allowable impact force was measured. The results obtained in this study are summarized as follows. 1. Machanical behavior of rough rice under impact loading was analyzed precisely and efficiently because measured data were accumulated and handled by this data acquisition system. 2. Rupture force and rupture energy of rough rice were appeared to be the lowest value in the range of 16 to 18 % moisture content, and rupture force and rupture energy of Japonica type were higher than those of Indica type in each level of moisture content. 3. From the result of the damage examined after the impact loading, allowable impact force was the lowest in the range of 16 to 18 % moisture content, and the value of the allowable impact force of Japonica type was higher than that of Indica type in each level of moisture content.