• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.281-287
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• 2004

In this paper, the refined plastic-hinge analysis accounting for gradual yielding with fibers on a section is developed. Geometric nonlinearities of member(P-δ) and frame(P-Δ) are accounted for by using stability functions. Residual stresses are considered by assigning initial stresses to the fiber on the section. The elastic core in a section is investigated at every loading step to determine the axial and bending stiffness reduction. The strain reversal effect is captured by investigating the stress change of each fiber. The proposed analysis proves to be useful in applying for practical analysis and design of three-dimensional steel frames.

• Structural Engineering and Mechanics
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• v.61 no.3
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• pp.397-406
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• 2017

The use of fiber reinforced polymer (FRP) for torsional strengthening of reinforced concrete (RC) single cell box beams has been analyzed considerably by researchers worldwide. However, little attention has been paid to torsional strengthening of multicell box girders in terms of both experimental and numerical research. This paper reports the experimental work in an overall investigation for torsional strengthening of multicell box section RC girders with externally-bonded Carbon Fiber Reinforced Polymer CFRP strips. Numerical work was carried out using non-linear finite element modeling (FEM). Good agreement in terms of torque-twist behavior, steel and CFRP reinforcement responses, and crack patterns was achieved. The unique failure modes of all the specimens were modeled correctly as well.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.141-146
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• 2002

In the present design concept, the nonlinear behavior of bridges is allowed under large earthquake. Therefore, demands for nonlinear analyses of bridges are increased more and more especially in the area of seismic assessment. It is, however, difficult to solve the problem how the nonlinearity of columns should be modelled. In this study, the fiber element Is adopted for model ins pier column. The element is a kind of structural elements like frame element, and it can model the distributed plasticity of plastic hinge. A 3 span continuos bridge is taken for seismic analysis. First, the nonlinear static analysis the column at fixed support are performed so that the characteristics of column is investigated. Second, the nonlinear dynamic analyses of the full bridge model is performed, considering 3 directional earthquake excitations.

• Advanced Composite Materials
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• v.16 no.2
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• pp.135-149
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• 2007

In the automobile industry, structural health monitoring of fiber reinforced polymer composite parts is a widespread need for maintenance before breakdown of the functional elements or a complete vehicle. High performance sensors are generally used in many of the structural health monitoring operations. Within this study, a carbon fiber sewing thread has been used as a low cost laminate failure sensing element. The experimentation plan was set up according to the electrical conductance and flexibility of carbon fiber threads, advantages of preforming operations, and sewing mechanisms. The influence of the single thread damages by changing the electrical resistance and monitoring the impact location by using carbon thread sensors has been performed. Innovative utilization of relatively cost-effective carbon threads for monitoring the delamination of metallic inserts from the basic composite laminate structure is a highlighting feature of this study.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.97-100
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• 2009

Fire resistance properties and mechanical properties of high strength concrete mock-up column using organic fiber by KS F 2257 Methods of fire resistance test for elements of building construction and compression test was investigated for application of precast concrete column method of high rise building in this study. As a test result, it was appeared that ECC permanent form is available as fire resistance method of high strength concrete and new precast concrete construction method for facilitating construction of high rise building.

• Composites Research
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• v.12 no.2
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• pp.36-45
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• 1999

Since carbon fiber epoxy composite materials have excellent properties for structures due to their high specific strength, high modulus, high damping and low thermal expansion, the hollow shafts made of carbon fiber epoxy composites have been widely used for power transmission shafts for motor vehicles, spindles of machine tools and rollers for film manufacturing. However, the molded composite shafts are not usually accurate enough for mechanical machine elements, which require turning or grinding of composite hollow shafts. In this paper, the grinding characteristics of composite hollow shafts, which are flexible in the radial and circumferential directions, were investiaged experimentally and analytically with respect to the stacking angle, thickness and outer diameter.

• Structural Monitoring and Maintenance
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• v.2 no.4
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• pp.357-382
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• 2015

This paper provides an overview of the use of different Distributed Optical Fiber Sensor systems (DOFSs) to perform Structural Health Monitoring (SHM) in the specific case of civil engineering structures. Nowadays, there are several methods available for extracting distributed measurements from optical fiber, and their use have to be according with the aims of the SHM performance. The continuous-in-space data is the common advantage of the different DOFSs over other conventional health monitoring systems and, depending on the particular characteristics of each DOFS, a global and/or local health structural evaluation is possible with different accuracy. Firstly, the fundamentals of different DOFSs and their principal advantages and disadvantages are presented. Then, laboratory and field tests using different DOFSs systems to measure strain in structural elements and civil structures are presented and discussed. Finally, based on the current applications, conclusions and future trends of DOFSs in SHM in civil structures are proposed.

• Journal of Plant Biology
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• v.28 no.1
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• pp.9-20
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• 1985

Dimensional variation of secondary xylem elements, such as vessel element and fiber, was investigated in root, stem and branch of Alnus hirsuta and A. firma. It is clear that vessel diameter in the root is the widest, next in the stem, and the least in the branch. Length of vessel element among them becomes, however, larger in following sequence; stem, root, and branch, whereas fiber diameter and length are the widest in the root, the second in the stem, and the least in the branch. The size of secondary xylem element at any one level in tree increases from the center (pith) of the organs through a number of annual rings to the outer.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.1
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• pp.63-73
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• 1991

Carbon fiber epoxy composite materials are widely used in the structures of aircrafts, robots and other machines because of their high specific strength, high specific stiffness and high damping. In order for the composite materials to be used in aircraft structures or machine elements, accurate surfaces for bearing mounting or joints must be provided, which require precise machining. In this paper, the machinability of the carbon fiber epoxy composite materials in turning was experimentally investigated. The cutting mechanism and the Taylor Tool Wear constants were determined and the surface roughness was measured w.r.t. cutting speeds and feed rates.

• Journal of Nutrition and Health
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• v.40 no.6
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• pp.558-565
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• 2007

On the basis of the increasing interest for the selection of beverages, this study aimed to evaluate the contents of nutrients and health ${\cdot}$ functional elements in the beverages. Total 161 beverages that bear nutrition lable (NL) as nutrition table and health ${\cdot}$ functional elements information were collected and classified to 8 groups. The evaluated nutrients that are obligatory for NL in Korea were total calorie, carbohydrate, protein, fat, and sodium. Presented values showed that milk & yogurt and soy milk are the most wholesome beverages while the total caloric contents also were higher among 8 groups. Sodium contents in soy milk were higher than any other groups. The caloric contents of other beverage groups come mainly from carbohydrate presumably simple sugar. The caloric content of sports drinks is the lowest but the sodium content is variable among products showing the range of 0 - 100 mg/100 ml. Nonobligatory nutrients for NL frequently expressed are Ca, Fe, vitamin C, folate, and dietary fiber. Their content per serving size does not exceed the tolerable upper intake level, however, habitual multiple intakes of certain product require attention for the prevention of overintakes. Many health ${\cdot}$ functional elements as catechin, carnitine, polyphenol, and nucleic acids etc were listed in NL without presenting the content and their functions appear to be exaggerated compared to the known scientific evidence.