• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.84-89
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• 2009

The objective of this research was to investigate the curing behavior and adhesion performance of urea-melamine-formaldehyde (UMF) resin for the four types of UMF-1, UMF-2, UMF-3, and UMF-4 which synthesized by the staged addition of melamine. Also, various network structures of these resin types were discussed based on their different curing behavior and adhesion performance. The curing behavior was evaluated by DMTA and thermal stability was checked by TGA. Adhesion performance was evaluated by dry and wet shear strengths and the pH value of each cured resin was checked to see its effect on the adhesion performance. The results indicated that the UMF-1 resin type by the addition of melamine initially with the urea and formaldehyde at the same F/(U+M) rate showed the lowest thermal stability, rigidity (${\Delta}E^{\prime}$), temperature of tan ${\delta}$ maximum ($T_{tan}\;_{\delta}$), and wet shear strength, and pH value of cured resin. In wet shear strength, however, the UMF-4 resin type appears to be slightly higher than UMF-1 resin type.

• Steel and Composite Structures
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• v.20 no.4
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• pp.801-812
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• 2016

In an actual design, none of the structures with shear behaviors will be designed for torsional moments. Any failure or damages to roofs, infills, shear walls, and braces caused by an earthquake, will inevitably result in relocation of center of mass and rigidity of the structure. With these changes, the dynamic characteristics of structure could be changed during an earthquake at any moment. The main objective of this paper is to obtain the relationship between time-varying eccentricity of load and corner lateral displacement. In this study, various methods have been used to determine the structural response for time-varying lateral corner displacement. As will be seen below, some of the structural calculation methods result in a significant deviation from the actual results, although these methods include the interaction effects of modes. Controlling the lateral displacement of structure can be performed in different ways such as, passive dampers, friction dampers, semi-active systems including the MR damper and active Systems. Selecting and locating these control systems is very important to bring the maximum safety with minimum cost into the structure. According to this study will be show the relation between the corner lateral displacements of structure and time-varying eccentricity by different kind of methods during an earthquake. This study will show that the response of the structure at the corners due to an earthquake can be very destructive and because of changing the eccentricity of load, calculating the maximum possible response of system can be carried out by this method. Finally, some kind of systems must be used for controlling these displacements. The results shows that, the CQC, DSC and exact methods is comply each other but the results of Vanmark method is not comfortable for these kind of buildings.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.365-373
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• 2008

Fiber Reinforced Polymer, FRP has a light weight, a high tensile strength based on design, non-electronic, non-magnetic, and rust-resistant feature, etc and many researches are being conducted recently on FRP in the construction area. Among them, GFRP (Glass Fiber Reinforced Polymer) is excellent in price competitiveness and is widely being used. However, since GFRP has a relative low modulus of elasticity and causes excessive deflection, the section must be large to be used as a structural component and an investigative review must be carried out in design to set the limit for deflection by the use load. Therefore, in order to solve the mentioned technical problems, this study suggested a section of a module form such that application of a large-scale section is possible. Also, to secure the low rigidity of FRP, this study developed a new FRP+ concrete composite girder form that confined the concrete. To identify the structural movement of the developed FRP+ concrete composite girder, shear strength test was carried out.

• Steel and Composite Structures
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• v.39 no.1
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• pp.95-107
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• 2021

In this work, the dynamic response of functionally graded beams on variable elastic foundations is studied using a novel higher-order shear deformation theory (HSDT). Unlike the conventional HSDT, the present one has a new displacement field which introduces undetermined integral variables. The FG beams were assumed to be supported on Winkler-Pasternak type foundations in which the Winkler modulus is supposed to be variable in the length of the beam. The variable rigidity of the elastic foundation is assumed to be linear, parabolic and sinusoidal along the length of the beam. The material properties of the FG porous beam vary according to a power law distribution in terms of the volume fraction of the constituents. The equations of motion are determined using the virtual working principle. For the analytical solution, Navier method is used to solve the governing equations for simply supported porous FG beams. Numerical results of the present theory for the free vibration of FG beams resting on elastic foundations are presented and compared to existing solutions in the literature. A parametric study will be detailed to investigate the effects of several parameters such as gradient index, thickness ratio, porosity factor and foundation parameters on the frequency response of porous FG beams.

• Steel and Composite Structures
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• v.43 no.2
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• pp.139-152
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• 2022

Steel-reinforced concrete (SRC) L-shaped column is the vertical load-bearing member with high spatial adaptability. The seismic behavior of SRC L-shaped column is complex because of their irregular cross sections. In this study, the hysteretic performance of six steel truss reinforced concrete L-shaped columns specimens under the combined loading of compression, bending, shear, and torsion was tested. There were two parameters, i.e., the moment ratio of torsion to bending (γ) and the aspect ratio (column length-to-depth ratio (φ)). The failure process, torsion-displacement hysteresis curves, and bending-displacement hysteresis curves of specimens were obtained, and the failure patterns, hysteresis curves, rigidity degradation, ductility, and energy dissipation were analyzed. The experimental research indicates that the failure mode of the specimen changes from bending failure to bending-shear failure and finally bending-torsion failure with the increase of γ. The torsion-displacement hysteresis curves were pinched in the middle, formed a slip platform, and the phenomenon of "load drop" occurred after the peak load. The bending-displacement hysteresis curves were plump, which shows that the bending capacity of the specimen is better than torsion capacity. The results show that the steel truss reinforced concrete L-shaped columns have good collapse resistance, and the ultimate interstory drift ratio more than that of the Chinese Code of Seismic Design of Building (GB50011-2014), which is sufficient. The average value of displacement ductility coefficient is larger than rotation angle ductility coefficient, indicating that the specimen has a better bending deformation resistance. The specimen that has a more regular section with a small φ has better potential to bear bending moment and torsion evenly and consume more energy under a combined action.

• Textile Coloration and Finishing
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• v.18 no.3 s.88
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• pp.49-58
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• 2006

The purpose of this study was to examine the effect of covering yarn's twist on mechanical properties of knitted fabrics of composite yarns with single covering process. Four yarns that were used in this study: two different composite yarns made from the four kinds of cotton and functional polyester-(Poly-A) with the ratio of 52:48, and the rest two yarns are the original cotton 100% yarn and the poly-A 100% yarn. The two kinds of composite yarns, CP1 and CP2, were processed on the single covering process. CP1 was applied on the single covering process with S-800 tpm, where Poly-A was used as covering yarn and cotton was used as core yarn. CP2 was applied on the same process as CP1 except that Poly-A had been applied on the two-for-one twisting process with S-400 tpm on the previous step. Sixteen mechanical properties of all the four knifed fabrics knitted under the same knitting conditions were measured by KES-FB system with the outer knit condition. And 3D CAD dressmaking simulations, which were driven by some of the mechanical properties, were presented. The results were as follows: CP2 had high RT values with twisting of covering yarn. CP2 also had high B, 2HB values because of higher linear density. SMD was affected rather by twisting of covering yarn than by fine hair of the cotton surface. Twisting of covering yarn made it decreasing T value and increasing W value. Dressmaking 3D CAD simulations showed that there are buckling effects on CP2 because of high bending rigidity and shear rigidity.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.8
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• pp.698-707
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• 2011

This paper is to analyze the stability of the thick plate on inhomogeneous Pasternak foundation, with linearly varying thickness and concentrated mass by finite element method. To verify this finite element method, the results of natural frequencies and buckling stresses by the proposed method are compared with the existing solutions. The dynamic instability regions are decided by the dynamic stability analysis of the thick plate on inhomogeneous Pasternak foundation, with linearly varying thickness and concentrated mass. The non-dimensional Winkler foundation parameter is applied as 100, 1000 and non-dimensional shear foundation parameter is applied as 5. The tapered ratios are applied as 0.25 and 1.0, the ratios of concentrated mass to plate mass as 0.25 and 1.0, and the ratio of in-plane force to critical load as 0.4. As the result of numerical analysis of the thick plate on inhomogeneous Pasternak foundation for $u{\times}v=300cm{\times}300cm$ and $a{\times}b=600cm{\times}600cm$, instability areas of the thick plate which has the larger rigidity of inner area are farther from ${\beta}$-axis and narrower than those which has the larger rigidity of outer area.

• Journal of the Korea Fashion and Costume Design Association
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• v.10 no.2
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• pp.125-138
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• 2008

For physical and hand property evaluation of fabrics, the knitted fabrics from 11 types of machines knitting fancy yarns, boucle (M1), knot (M2), snarl (M3), and slub (M4), tamtam (M5), tubular (M6), fur 1 (M7), bead (M8), fur 2 (M9), fur 3 (M10), and ladder (M11) yarns, were prepared with 7-10 G plain stitch. Washing test and pilling test had also been carried out. For hand properties by objective sensibility evaluation, 17 items of sir mechanical properties using KES-FB (Kawabata Evaluation System) had been measured. Then hand values of knitted fabrics were calculated with a calculation formula, namely KN-402-KT. Finally the total hand values were obtained through KN-301-WINTER. As a result of physical properties and objective evaluation for machines knitting fancy fabrics, most of them shrank in the direction of wale and course after the washing test, in which their shrinkage rate had a maximum of 3.5%. Therefore, the washing test indicated that the shrinkage ratio of knitted fabrics had a minor change. The results of the pilling test are mostly 4-5th grade, and all of the machines knitting fancy fabrics showed good results in the pilling resistance. In hand properties and objective sensibility evaluation, twisted fancy yarns, such as boucle (M1), knot (M2), snarl (M3), and slub (M4), were superior to bonding rigidity (B) and shear rigidity (G). The surface property between course and wale differs in all samples and course direction is tougher than wale direction. FUKURAMI (fullness and softness) of all samples have high values, besides NUMERI (smoothness) of tamtam (M5) and boucle (M1), which were rather good. Most samples except fur 1 (M7) had low KOSHI (stiffness) value. The total hand value (THV) of twisted yarns was low. This study proves that manufacturers, who plan knitting yarn products and knit fashion, can apply these data to develop machines knitting yarns and knits that fit the consumers' demands.

• Steel and Composite Structures
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• v.48 no.2
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• pp.207-233
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• 2023

Steel-concrete composite box girder bridges are widely used in the construction of highway and railway bridges both domestically and abroad due to their advantages of being light weight and having a large spanning ability and very large torsional rigidity. Composite box girder bridges exhibit the effects of shear lag, restrained torsion, distortion and interface bidirectional slip under various loads during operation. As one of the most commonly used calculation tools in bridge engineering analysis, one-dimensional models offer the advantages of high calculation efficiency and strong stability. Currently, research on the one-dimensional model of composite beams mainly focuses on simulating interface longitudinal slip and the shear lag effect. There are relatively few studies on the one-dimensional model which can consider the effects of restrained torsion, distortion and interface transverse slip. Additionally, there are few studies on vehicle-bridge integrated systems where a one-dimensional model is used as a tool that only considers the calculations of natural frequency, mode and moving load conditions to study the dynamic response of composite beams. Some scholars have established a dynamic analysis model of a coupled composite beam bridge-train system, but where the composite beam is only simulated using a Euler beam or Timoshenko beam. As a result, it is impossible to comprehensively consider multiple complex force effects, such as shear lag, restrained torsion, distortion and interface bidirectional slip of composite beams. In this paper, a 27 DOF vehicle rigid body model is used to simulate train operation. A two-node 26 DOF finite beam element with composed box beams considering the effects of shear lag, restrained torsion, distortion and interface bidirectional slip is proposed. The dynamic analysis model of the coupled composite box girder bridge-train system is constructed based on the wheel-rail contact relationship of vertical close-fitting and lateral linear creeping slip. Furthermore, the accuracy of the dynamic analysis model is verified via the measured dynamic response data of a practical composite box girder bridge. Finally, the dynamic analysis model is applied in order to study the influence of various mechanical effects on the dynamic performance of the vehicle-bridge system.

• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.595-604
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• 2000

Web openings of large beams provide space for wiring, piping, and duct work to provide for proper drainage, pipes and duct must be slightly sloped with the attendant result that all web openings can not be centered on the centroidal axes of the beams. Test specimens are made for opening-depth to beam-depth ratio of 0.5 and for eccentricities of the opening center line of 10% from middepth of the beam because of the proximity of the opening edge to the flange. In this paper, available test results and theories relating to the strength of composite beams having eccentric rectangular openings are surveyed and experiments were carried out to examine the structural behaviors. In all the tests in this paper good agreement is demonstrated with maximum loads measured in tests, and observed failure modes Furthermore, compared with analytical values and experimental values of interaction diagram between moment and shear capacity were safed as it is scattered with outer part of the analytical values.