• Structural Engineering and Mechanics
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• v.70 no.3
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• pp.269-277
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• 2019

Using the non-local elasticity theory, Timoshenko beam model is developed to study the non- local buckling of Triple-walled carbon nanotubes (TWCNTs) embedded in an elastic medium under axial compression. The chirality and small scale effects are considered. The effects of the surrounding elastic medium based on a Winkler model and van der Waals' (vdW) forces between the inner and middle, also between the middle and outer nanotubes are taken into account. Considering the small-scale effects, the governing equilibrium equations are derived and the critical buckling loads under axial compression are obtained. The results show that the critical buckling load can be overestimated by the local beam model if the small-scale effect is overlooked for long nanotubes. In addition, significant dependence of the critical buckling loads on the chirality of zigzag carbon nanotube is confirmed. Furthermore, in order to estimate the impact of elastic medium on the non-local critical buckling load of TWCNTs under axial compression, the use of these findings are important in mechanical design considerations, improve and reinforcement of devices that use carbon nanotubes.

• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.417-430
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• 2023

As the key part in the reinforced concrete column-steel beam (RCS) frame, the beam-column joints are usually subjected the axial force, shear force and bending moment under seismic actions. With the aim to study the seismic behavior of RCS joints with and without RC slab, the quasi-static cyclic tests results, including hysteretic curves, slab crack development, failure mode, strain distributions, etc. were discussed in detail. It is shown that the composite action between steel beam and RC slab can significantly enhance the initial stiffness and loading capacity, but lead to a changing of the failure mode from beam flexural failure to the joint shear failure. Based on the analysis of shear failure mechanism, the calculation formula accounting for the influence of RC slab was proposed to estimate shear strength of RCS joint. In addition, the finite element model (FEM) was developed by ABAQUS and a series of parametric analysis model with RC slab was conducted to investigate the influence of the face plates thickness, slab reinforcement diameter, beam web strength and inner concrete strength on the shear strength of joints. Finally, the proposed formula in this paper is verified by the experiment and FEM parametric analysis results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.3
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• pp.551-569
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• 2024

With the rapid development of electric vehicles (EVs) industry, EV charging service becomes more and more important. Especially, in the case of suddenly drop of air temperature or open holidays that large-scale EVs seeking for charging devices (CDs) in a short time. In such scenario, inefficient EV charging scheduling algorithm might lead to a bad service quality, for example, long queueing times for EVs and unreasonable idling time for charging devices. To deal with this issue, this paper propose a Deep-Q-Network (DQN) based two-stage scheduling method for the large-scale EVs charging service. Fine-grained states with two delicate neural networks are proposed to optimize the sequencing of EVs and charging station (CS) arrangement. Two efficient algorithms are presented to obtain the optimal EVs charging scheduling scheme for large-scale EVs charging demand. Three case studies show the superiority of our proposal, in terms of a high service quality (minimized average queuing time of EVs and maximized charging performance at both EV and CS sides) and achieve greater scheduling efficiency. The code and data are available at THE CODE AND DATA.

• Steel and Composite Structures
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• v.52 no.4
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• pp.451-460
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• 2024

Hollow reinforced concrete columns confined with GFRP tubes (GRCH) are composite members composed of the outer GFRP tube, the PVC or other plastic tube as the inner tube, and the reinforced concrete between two tubes. Because of their high ductility, light weight, corrosion resistance and convenient construction, many researchers pay attention to the composite members. However, there are few studies on GRCH members under eccentric compression compared with those under axial compression. Eight hollow columns were tested under eccentric compression, including one axial compression column and seven eccentric compression columns. The failure modes and force mechanisms of GRCH members were analyzed, considering the varying in hollow ratio, reinforcement ratio and eccentricity. The test results showed that configuring steel bars can greatly increase the bearing capacity and ductility of the members. Each component (GFRP tube, concrete, steel bar) had good deformation coordination and the strength of each material could be fully utilized. But for specimens with larger eccentricity ratio (e_r=0.4) and larger hollow ratio (χ=0.55), the restraining effect of GFRP tube on concrete was significantly decreased.

• Conservation Science in Museum
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• v.29
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• pp.47-64
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• 2023

Daehye Bogakseonsaseo (Letters of Master Bogak) in the possession of the National Museum of Korea is a Goryeo-era book produced in 1387, which was acquired in 2005 in a state of severe general damage. Subsequently, its production techniques and materials were examined using bibliographical characteristics and scientific analysis, based on which an overall conservation treatment was carried out. Janghwang(mounting) in bibliographical characteristics is a five-hole-stitch binding (五針眼線裝本), a single-lined rectangular box (四周單邊), and no column lines. The conservation treatment was examined in two aspects: the basic form and the conservation treatment process. The book is composed of the outer cover, original cover, end paper, and inner paper of 0.04-0.07mm thick, which is significantly thinner than general book paper. The conservation treatment was applied after the entire book was disassembled, based on the assessment that both the cover and the inner sheets of paper were in a dire condition due to deterioration. The conservation treatment comprised of the process of disassembly, cleaning, reinforcement of defective parts, scanning, and binding, with a paulownia box made for its storage. At the time of disassembly, samples were made for the inner sheets and the book string in order to conduct fiber identification. The fibers were identified using Safranin and C-stains. Safranin staining identified a thick fiber wall, in addition to cross-marking, dislocation, and transparent membranes. C-stain staining identified the fiber as mulberry, given the dark red residue. The book strap has a flat, circular cross-section, and was identified as cotton fiber, since a lumen was observed in the center.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1A
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• pp.69-78
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• 2008

In this study, in order to verify the reinforcement effects of the cracked concrete tubes and culverts, static load test was conducted. After the load carrying capacity of the original concrete tubes (nominal diameter 0.8 m, 1.0 m, 1.5 m) and box culverts (inner width 2.0 m. 2.5 m) was reduced by the cracking test, the cracked concrete specimens were strengthened by installing profile with steel stiffener and high strength mortar. And then, the maximum load tests were conducted the renewal concrete tubes and box culverts. According to the method application, the load carrying capacity increased 1.66~3.50 times than it of the original tubes before applying the method. In case of the original box culverts, the load carrying capacity increased 1.66~3.10 times than the case before installing profile and high strength mortar. Also non-linear analysis was carried out by using the commercial FEM program of ABAQUS 6.6. Solid (C3D8R) elements and concrete damage plasticity option was applied to the analysis. For reflecting confined reinforcing bars in the analysis, the composite material properties were used.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.267-275
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• 2009

The steel pipe of steel-concrete composite piles increases the pile strength and induces the ductile failure by constraining the deformation of the inner concrete. In this research, the load-movement relations and the reinforcement effect by the outer steel pipe in the steel-concrete composite pile were analyzed by performing three-dimensional numerical analyses, which can simulate the yielding behavior of the pile material and the elasto-plastic behavior of soils. The parameters analyzed in the study include three pile materials of steel, concrete and composite, pile diameter and loading direction. As the results, the axial capacity of the composite pile was 1.9 times larger than that of the steel pipe pile and similar with that of the concrete pile. At the allowable movement criteria, the horizontal capacity of the composite pile was 1.46 times larger than that of the steel pile and 1.25 times larger than that of the concrete pile. In addition, the horizontal movement at the pile head of the composite pile was about 78% of that of the steel pile and about 53% of that of the concrete pile, which showed that the movement reduction effect of the composite pile was significant and enables the economical design of drilled shafts.

• Journal of the Korea Institute of Building Construction
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• v.24 no.4
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• pp.447-458
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• 2024

This study investigates the effectiveness of Building Information Modeling(BIM) software, specifically SketchUp and Revit, in reducing errors during quantity take-off(QTO) for complex building elements. While 3D modeling offers advantages, existing software may not fully account for manufacturing discrepancies, such as variations in concrete cover thickness and reinforcing bar radius. To address this limitation, this research proposes a BIM-based QTO method for high-insulation wall panels with intricate details. The method utilizes a BIM family library, focusing on key parameters like concrete cover thickness and inner radius of shear reinforcement. A case study compared the cross-sectional details of a wall panel modeled in Revit with the actual manufactured specimen. The analysis revealed a 12% reduction in modeled concrete cover thickness and a 1.27 times larger modeled inner radius of the shear bar compared to the real-world values. The proposed method incorporates these manufacturing variations into the Revit model of the high-insulation wall panel. Software like Navisworks facilitates the identification and correction of any material interferences arising from these adjustments. Furthermore, the method employs a unit wall concept(1m²) to account for the volume of various materials, including insulation and splice sleeves at joints. This allows for the identification of a similar existing family within the BIM library(e.g., "Double RC wall with embedded insulation") that reflects the actual material quantities used in the wall panel. By incorporating these manufacturing-induced variations, the proposed method offers a more accurate QTO process for complex high-insulation wall panels. The "Double RC wall with embedded insulation" family within the Revit program serves as a valuable tool for material quantity estimation in such scenarios.

• Journal of the Korean GEO-environmental Society
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• v.13 no.1
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• pp.37-43
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• 2012

Generally levee or revetment becomes weak by erosion (scour) due to saturation of ground with infiltration, flowing water. So when levee or revetment is constructed, slope reinforcement must be installed to prevent failure. In this study experimental test was performed for verifying shear resistance, horizontal permeability and rooting ability of Geocomb designed to address the shortcomings of 3-dimension Geocell. Geocomb is one of geosynthetics and the advanced system of geogrid. According to the results of shear test, internal friction angle of reinforced ground with Geocomb was increasing compared with existing material and horizontal permeability of ground with Geocomb was bigger than geocell, porous geocell reinforcing ground. Lastly rooting ability of geocomb is most excellent. These results determined for the inner surface of the cell is net structure.

• The Journal of the Korea Contents Association
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• v.11 no.12
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• pp.307-316
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• 2011

The objective of this study is to figure out some specific features that were found during the adaptation process of migrant women by marriage to their local community, and also to elicit certain practical implications to facilitate their adaptation, based on the findings. For data collection, in-depth interviews were conducted with eight migrant women by marriage and the interviews were tape-recorded for transcription. For analysis, phenomenological method, particularly, Colaizzi method was adopted, by which meaningful statements in the data were categorized into themes and theme clusters. A total of 7 thematic unts, 17 themes and 47 meanings were elicited from the analysis and these 7 thematic units were "reinforcement of inner capability"; "cultural assimilation"; "to be a limited benefit receiver"; "no human network"; " impossible to be optimistic about future"; "hoping to reside in their local community"; "possible to leave Korea." Finally, this study suggested the implications for social welfare practices to facilitate the adaptation of immigrant women by marriage in their local community.