• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.57-60
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• 2008

Compared with a steel-reinforced section with equal areas of longitudinal reinforcement, a cross section using FRP flexural reinforcement after cracking has a smaller depth to the neutral axis because of the lower axial stiffness. The compression region of the cross section is reduced, and the crack widths are wider. As a result, the shear resistance provided by both aggregate interlock and compressed concrete is smaller. Research on the shear capacity of flexural members without shear reinforcement has indicated that the concrete shear strength is influenced by the stiffness of the flexural reinforcement. In this research, experimental observations were made for the shear strength of FRP reinforced concrete beam and validity of existing predicting equations were examined. Test results showed that shear strength decreased as shear-span increased.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2010.04a
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• pp.389-394
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• 2010

A concrete filled square steel tube (CFT) is composed of the external steel material, which its strength is reduced in fire due to sudden temperature increase, and the internal concrete with high thermal capacity that can ensure the fire resistance performance of the structure. Therefore, research about the influence factors of the structural performance of CFT column is required in order to apply CFT column to a fire resisting structure, and additional research about influence for each condition is also necessary. Among the influence factors, the boundary condition between column and beam is important structurally, and it is one of the major factors that determine overall fire resisting performance. This study performed a fire experiment under loading in order to analyse the influences of CFT column to the boundary condition. As the results of the experiment, fire resistance time of 106 minutes was ensured for the clamped-end condition but 89 minutes for the hinge-end condition in case of the 360 cross section. And, fire resistance time of 113 minutes was ensured for the clamped-end condition but 78 minutes for the hinge-end condition in case of the 280 cross section. The difference in the fire resistance performance according to changes in the boundary conditions showed a tendency that larger change effect on the fire resistance performance was derived from smaller cross section area.

• Steel and Composite Structures
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• v.34 no.3
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• pp.393-407
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• 2020

The braced tube frame system, a combination of perimeter frame and bracing frame, is one of the systems used in tall buildings. Due to the implementation of this system in tall buildings and the high rigidity resulting from the use of general bracing, providing proper ductility while maintaining the strength of the structure when exposing to lateral forces is essential. Also, the high stress at the connection of the beam to the column may cause a sudden failure in the region before reaching the required ductility. The use of Reduced Beam Section connection (RBS connection) by focusing stress in a region away from beam to column connection is a suitable solution to the problem. Because of the fact that RBS connections are usually used in moment frames and not tested in tall buildings with braced tube frames, they should be investigated. Therefore, in this research, three tall buildings in height ranges of 20, 25 and 30 floors were modeled and designed by SAP2000 software, and then a frame in each building was modeled in PERFORM-3D software under two RBS-free system and RBS-based system. Nonlinear time history dynamic analysis is used for each frame under Manjil, Tabas and Northridge excitations. The results of the Comparison between RBS-free and RBS-based systems show that the RBS connections increased the absorbed energy level by reducing the stiffness and increasing the ductility in the beams and structural system. Also, by increasing the involvement of the beams in absorbing energy, the columns and braces absorb less energy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.219-226
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• 2005

In this study, the problem formulation and solution technique using genetic algorithms for design optimization of laminate composite cylindrical beam section are presented. The hollow cylindrical beams we usually used in the wheel chair. If the weight of wheel chair is reduced, it will lead to huge improvement in passenger's mobility and comfort. In this context, the replacement of steel by high performance and light weight composite material along with optimal design will be a good contribution in the process of weight reduction of a wheel chair. An artificial genetics approach for the design optimization of hollow cylindrical composite beam is presented. On applying the genetic algorithm, the optimal dimensions of hollow cylindrical composite beams which have equivalent rigidities to those of corresponding hollow cylindrical steel beams are obtained. Also structural analysis is conducted on the entire wheel chair structure incorporating Tsai-Wu failure criteria. The maximum Tsai-Wu failure criteria index is $0.192\times10^{-3}$ which is moth less than value of 1.00 indicating no failure is observed under excessive loading condition. It is found that the substitution of steel by composite material could reduce the weight of wheel chair up to 45%.

• Journal of Animal Science and Technology
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• v.52 no.3
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• pp.237-244
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• 2010

In order to investigate the physiological properties of velvet antler of elk (Cervus e. canadensis) raised in Korea, antlers (n=378) were collected from deer in 8 provinces including Gyeonggi-do (n=53), Gangwon-do (n=49), Chungcheongbuk-do (n=62), Chungcheongnam-do (n=68), Jeollabuk-do (n=52), Jeollanam-do (n=15), Gyeongsangbuk-do (n=30) and Gyeongsangnam-do (n=49). The exterior characteristics (weight, length, girth and crown) of all antlers were measured, and 18 antler samples were randomly selected for measurement of interior characteristics such as specific gravity, capacity and diameter of cross section. The mean antler weight, length of the main beam and mean length of upper section were $4.87{\pm}1.79\;kg$, $83.7{\pm}13.2\;cm$ and $40.6{\pm}11.4\;cm$, respectively. Mean girth of the top, middle and base of the main beam were $27.1{\pm}5.9\;cm$, $22.1{\pm}3.6\;cm$ and $22.9{\pm}3.6\;cm$ respectively, indicating a slight narrowing in the middle of the antler. In each of the tines, the girth at the base was markedly thicker compared to the top. The depth of the crown at the top of the antler, and the average number of crowns and tines were $14.1{\pm}7.0\;cm$, $2.1{\pm}0.6$ and $3.0{\pm}0.5$, respectively. Although there was no significant difference in mean specific gravity between top and base, mean specific gravity of main beam tended to increase from top to base of the antler with decreasing capacity. Additionally, the inner diameter of the base of the antler was significantly reduced compared to that of the top, indicating a greater integumental thickening due to mineralization. Information on the morphological and physiological properties of elk antlers is scarce. Therefore, these results may be useful in providing basic information for the physiological properties of antler, and encourage further studies on antler morphology in other deer species showing species specific differences.

• Fire Science and Engineering
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• v.24 no.6
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• pp.69-75
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• 2010

A concrete filled square steel tube (CFT) is composed of the external steel material, which its strength is reduced in fire due to sudden temperature increase, and the internal concrete with high thermal capacity that can ensure the fire resistance performance of the structure. Therefore, research about the influence factors of the structural performance of CFT column is required in order to apply CFT column to a fire resisting structure, and additional research about influence for each condition is also necessary. Among the influence factors, the boundary condition between column and beam is important structurally, and it is one of the major factors that determine overall fire resisting performance. This study performed a fire experiment under loading in order to analyse the influences of CFT column to the boundary condition. As the results of the experiment, fire resistance time of 106 minutes was ensured for the clamped-end condition but 89 minutes for the hinge-end condition in case of the 360 cross section. And, fire resistance time of 113 minutes was ensured for the clamped-end condition but 78 minutes for the hinge-end condition in case of the 280 cross section.

• Structural Engineering and Mechanics
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• v.47 no.6
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• pp.819-838
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• 2013

This paper summarises the results of an experimental study to investigate the flexural behaviour of reinforced concrete beams strengthened using carbon-fibre reinforced polymer (CFRP) laminate in four-point bending. The experimental parameters included are the reinforcing bar ratio ${\rho}_s$ and preload level. Four bar ratios were selected (${\rho}_s=0.13$ to 0.86%), representing the section of two longitudinal tensile reinforcements, with diameters of 8, 14, 16, and 20 mm in order to reveal the effect of bar ratio on failure load and failure mode. Eight beams that could be considered "full-scale" in size, measuring 200 mm in width, 400 mm in total height and 2300 mm in length, were tested. Three beams were selected with different bar ratios (${\rho}_1$, ${\rho}_2$, ${\rho}_3$), and considered as control specimens (without ), while three other beams identical to the control beams with the same CFRP laminates ratio and a seventh beam with ${\rho}_{min}$ (the lowest bar ratio) were also used. In the second part of the study, two beams with the bar ratio ${\rho}_2$ were preloaded at two levels, 50 and 100% of their ultimate loads, and then repaired. This experimental investigation was consolidated using an analytical model. The experimental and analytical results indicate that the flexional capacity and stiffness of strengthened and repaired beams using CFRP laminate were increased compared to those of control beams, and the behaviour of repaired beams was nearly similar to the undamaged and strengthened beams; unlike the ductility of strengthened beams, which was greatly reduced compared to the control.

• Journal of the Korea Convergence Society
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• v.10 no.8
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• pp.145-151
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• 2019

In this study, the effects were analyzed by applying the vibration absorption liner into the guide rail bracket as a part of method to reduce the vibration and noise on the high-rise apartment. As the result of vibration absorption liner performance, it was checked that the level of vibration and noise was reduced around 65.49% in the car side and around 90.05% in the counterweight side. Therefore, the vibration absorption effect by the vibration absorption liner of elevator guide rail bracket became fairly good. In case of the vibration absorption liner application, there was an effect on the reduction of 7.26 to 22.22% at hoistway section area, 3,840,000 to 9,780000 KRW at the cost of material and installation by comparing with the damping beam application. Also, in case of the vibration absorption liner application with light weight instead of damping beam with heavy weight, it was thought to become significant effect at preventing the safety from the accidents on installation site.

• Coupled systems mechanics
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• v.12 no.3
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• pp.199-220
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• 2023

This article presents a new analytical model to study the effect of porosity on the shear correction factors (SCFs) of functionally graded porous beams (FGPB). For this analysis, uneven and logarithmic-uneven porosity functions are adopted to be distributed through the thickness of the FGP beams. Critical to the application of this theory is a determination of the correction factor, which appears as a coefficient in the expression for the transverse shear stress resultant; to compensate for the assumption that the shear strain is uniform through the depth of the cross-section. Using the energy equivalence principle, a general expression is derived from the static SCFs in FGPB. The resulting expression is consistent with the variationally derived results of Reissner's analysis when the latter are reduced from the two-dimensional case (plate) to the one-dimensional one (beam). A convenient algebraic form of the solution is presented and new study cases are given to illustrate the applicability of the present formulation. Numerical results are presented to illustrate the effect of the porosity distribution on the (SCFs) for various FGPBs. Further, the law of changing the mechanical properties of FG beams without porosity and the SCFare numerically validated by comparison with some available results.

• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.195-206
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• 2005

Experimental research was performed on the 6m-6m two-span, continuous composite beams. Background research for the crack width control of continuous composite bridges in the Eurocode-4 is reviewed and equationsfor the calculation of crack width considering tension stiffening are presented. The behavior of the continuous composite beams was investigated using the initial and stabilized cracking process of the concrete slab in tension. Test results showed that the current requirement of minimum reinforcement for ductility in Korea Highway Bridge Design Codes could be reduced. The flexural stiffness of cracked continuous composite beams can be evaluated by the uncracked section analysis until the stabilized cracking stage. An empirical equation for the relationship between the stress of tensile reinforcements and crack width was obtained from the test results.