• Steel and Composite Structures
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• v.35 no.3
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• pp.439-447
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• 2020

This paper presents two sets of full three-dimensional thermoelastic finite element analyses of superimposed thermo-mechanically loaded Spar Wingskin Joints made with laminated Graphite Fiber Reinforced Plastic composites. The study emphasizes the influence of residual thermal stresses and material anisotropy on the inter-laminar delamination behavior of the joint structure. The delamination has been pre-embedded at the most likely location, i.e., in resin layer between the top and next ply of the fiber reinforced plastic laminated wingskin and near the spar overlap end. Multi-Point Constraint finite elements have been made use of at the vicinity of the delamination fronts. This helps in simulating the growth of the embedded delamination at both ends. The inter-laminar thermoelastic peel and shear stresses responsible for causing delamination damage due to a combined thermal and a static loading have been evaluated. Strain energy release rate components corresponding to the Mode I (opening), Mode II (sliding) and Mode III (tearing) of delamination are determined using the principle of Virtual Crack Closure Technique. These are seen to be different and non-self-similar at the two fronts of the embedded delamination. Residual stresses developed due to the thermoelastic anisotropy of the laminae are found to strongly influence the delamination onset and propagation characteristics, which have been reflected by the asymmetries in the nature of energy release rate plots and their significant variation along the delamination front.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.177-184
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• 2011

In this paper the nonlinear analysis that include time-dependent characteristics of materials and geometric nonlinearity of elements for the cable-stayed PSC bridges is presented. Analysis models for finite element method were developed based on the flexibility based fiber beam-column model originally proposed by Spacone et al.(1996). The developed analysis model implemented in general purpose object-oriented finite element analysis program named HFC(Cho 2009). The performance of proposed analysis models is evaluated by comparing with the former results of the design data. The deflection of time dependent analysis is larger than time ignored analysis on construction sequences, and the bridge is destructed at a smaller deflection than the time ignored analysis on failure behavior.

• Korean Journal of Materials Research
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• v.19 no.3
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• pp.142-150
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• 2009

In this paper, non-treated ACF (Activated Carbon Fiber) /$TiO_2$ and Zn-treated ACF/$TiO_2$ were prepared. The prepared composites were characterized in terms of their structural crystallinity, elemental identification and photocatalytic activity. XRD patterns of the composites showed that the non-treated ACF/$TiO_2$ composite contained only typical single and clear anatase forms while the Zn-treated ACF/$TiO_2$ contained a mixed anatase and rutile phase with a unique ZnO peak. SEM results show that the titanium complex particles are uniformly distributed on and around the fiber and that the titanium complex particles are more regularly distributed on and around the ACF surfaces upon an increase of the $ZnCl_2$ concentration. These EDX spectra show the presence of peaks from the C, O and Ti elements. Moreover, peaks of the Zn element were observed in the Zn-treated ACF/$TiO_2$ composites. The prominent photocatalytic activity of the Zn-treated ACF/$TiO_2$ can be attributed to the three different effects of photo-degradation: doping, absorptivity by an electron transfer, and adsorptivity of porous ACFs between the Zn-$TiO_2$ and Zn-ACF.

• Journal of Korean Association for Spatial Structures
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• v.9 no.3
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• pp.67-74
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• 2009

Presently means of utilizing sensors such as Piezoelectric(PZT) Element for evaluating the affect of oscillator, strain gauge for analyzing physical changes and use of Fiber Bragg Grating(FBG) Sensor are widely practiced in the field. In this study, PZT and FBG sensors were used to tearing damage of cable systems in these sensors. Cable systems are a construction of elements carrying only tension and no compression or bending in membrane structure. But damage detection of cable systems by using existing safety diagnosis is difficult to detect the characteristic change of overall structural action. If cable snaps are occurred to cable release and tear in tension structures, these are set up a vibration. So, we used piezo-electric materials and result of experiment using this was compared with result of experiment using FBG sensors The purpose of this research is to develop of damage detection method of cable system in tensile stress.

• Journal of the Korea Fashion and Costume Design Association
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• v.21 no.1
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• pp.103-113
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• 2019

The purpose of this study was to develop an e-textile using LEDs that can enhance visual and functional effects, and to identify their applicability to sportswear. By applying the design elements of fashion design concretely with LEDs, an e-textile design module is developed and that module is applied to the product, so LED application design can be proposed for use in a practical product. E-textiles have been divided into five categories, and their usefulness were verified by applying e-textiles to men's and women's sportswear. The product beign considered has a built-in tilt sensor, which illuminates the LEDs according to the user's movements, and allows the LEDs to be turned on or off in accordance to the user's preference. E-tatoo is a type of LED application that enhances the appearance by placing LEDs on a small area, emphasizing origin points, just like an actual tattoo. Designed with LEDs arranged in a straight line and various curved forms, e-strips can provide a function that matches the characteristics of each section of clothing or fashion item. E-wappen uses about 7-10 LEDs to give motifs a strong sense of visibility, thus adding to their vibrancy. E-panels and e-clothes were able to produce creative and high-value textures. It is also expected to be used for special purposes or bags as it is possible to produce high value-added textures that are creative and aesthetically beautiful. For instance, a progressive LED string on the straight line of female leggings can further emphasize rhythmic movements during exercise, and e-wappen also serves the purpose of nighttime protection. It is also believed that the application of dance or dance-related sportswear will make the movement of the performance more intense and lively.

• Textile Coloration and Finishing
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• v.33 no.2
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• pp.72-78
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• 2021

The purpose of this study, the purpose of this study is to activate the antibacterial effect on the Chlorinated polyvinyl chloride film by using Octadecyldimethyl (3-triethoxy silylpropyl) ammonium chloride antibacterial agent with Chlorinated polyvinyl chloride polymer, which is inexpensive and has excellent properties such as heat resistance and chemical resistance. The Chlorinated polyvinyl chloride polymer was dissolved in a dimethylacetamide solvent, and film samples were prepared by varying the ratio of Octadecyldimethyl (3-triethoxy silylpropyl) ammonium chloride to study the antibacterial performance. A Scanning Electron Microscope-Energy Dispersive X-ray Spectrometer and X-ray photoelectron spectroscopy were employed to confirm the elements in the samples. According to the initial decomposition temperature of the Chlorinated polyvinyl chloride film and the Chlorinated polyvinyl chloride/Octadecyldimet hyl (3-triethoxy silylpropyl) ammonium chloride(10%) film using a Thermogravimetric analyzer(TA-DTA), it was confirmed that the initial decomposition temperature was lowered due to the influence of Octadecyldimethyl (3-triethoxy silylpropyl) ammonium chloride. In addition, in order to measure the mechanical properties, Universal testing machine was used and the result showed that a strength of Chlorinated polyvinyl chloride/Octadecyldimethyl (3-triethoxy silylpropyl) ammonium chloride(10%) was 36.8 MPa. The antimicrobial properties of the Chlorinated polyvinyl chloride/Octadecyldimethyl (3-triethoxy silylpropyl) ammonium chloride(10%) film showed 99.9% antimicrobial properties.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.193-204
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• 1997

In order to quantify the relationships of the important physical factors relating failure to strong earthquake loading, the plastic fatigue problems for structural components under repeated loading were reviewed first. A new concept of very low cycle fatigue failure for structural components under severe cyclic excitations as in strong earthquakes was represented. Also, an experimental study was made of the very low cycle fatigue failure of structural steel elements. It was attempted to realize the ultimate failure in the course of loading repetitions of the order of several to twenty. The test specimen had a form of rectangular plate, representing a thin-plated element in a steel member as wide-flange cross section. It was subjected to uniaxial loading repeatedly, until complete failure takes place after undergoing inelastic buckling, plastic elongation and/or their combination. It was seen as a result that the state of the ultimate failure is closely related to the maximum strain at the extreme fiber in the cross section.

• Journal of Korean Society of Steel Construction
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• v.16 no.4 s.71
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• pp.493-500
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• 2004

In this study, the effects of ring stiffeners for buckling of cylindrical shells with composite materials were analyzed. The finite element method was used: 3-D beam elements were used for stiffeners and flat shell elements were used for cylindrical shells and were improved by introducing a substitute shear strain. The ring stiffeners were of the transverse rib type. The buckling behaviors of the cylindrical shells were analyzed based on various parameters, such as locations and sizes of stiffeners, diameter/length ratios and boundary conditions of shells, and fiber-reinforced angles. Effective reinforcement was examined by understanding the exact behaviors for buckling. The results of the analysis may serve as references for designs and future investigations.

• Journal of the Korean Institute of Educational Facilities
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• v.19 no.5
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• pp.29-36
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• 2012

The goals of this study are to develop a sprayable strain-hardening cement composite (SHCC) and to investigate the potential of the sprayable SHCC for packing the joint between existing R/C building and seismic retrofit elements. This paper provides the procedure for the development of a sprayable SHCC, test results of fresh properties required to a sprayable SHCC, and mock-up test results of developed sprayable SHCC. Control mixture of polyvinyl alcohol (PVA) fiber-reinforced SHCC (PVA-SHCC) was predetermined based on available research results. The pumpability and sprayability of the SHCC mixture were depended on the fluid property of fresh SHCC mixture. In this study, the effects of admixtures such as AE agent and fly ash on the rheological and rebound properties of control SHCC mixture were investigated to determine a sprayable SHCC mixture. Flow values and air content during shotcreting procedure of sprayable SHCC were also evaluated. The results show that flow or flowability and amount of air of three SHCC mixtures decreased almost linearly according to shotcreting procedure from mixer to nozzle. And the pumpability and sprayability of mixture with AE agent and low amounts of fly ash were superior to the those of SHCC. Mock-up test result show that developed sprayable SHCC indicates much improved workability and shotcrete construction period than conventional method(nonshrinkage mortar).

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.13-16
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• 2008

Corbels are short cantilevers that project from the faces of a column and are a type of stress disturbed member, resisting both the ultimate shear force applied to them by the beam, and the ultimate horizontal force caused by shrinkage, temperature changes, and creep of the supported elements. Recently, as there have been an increase in the use of high-strength concrete and the concern about corrosion problems, lots of researches about hybrid reinforcing technique, applying strategically high performance reinforcements to the concrete elements, are performed. In this study, fiber reinforced high strength concrete corbels were constructed and tested for applying hybrid reinforcing technique to the corbels using steel fibers and headed bars. The results showed that the performance in terms of load carrying capacities, stiffness, ductility, and crack width was improved, as the steel fibers were added and the percentage of steel fibers was increased. In addition, the corbel specimens used headed bars as main tension ties showed superior load carrying capacities, stiffness, and ductility to the corbel specimens anchored main tension ties by welding to the transverse bars.