• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.5B
• /
• pp.313-320
• /
• 2012

A hybrid floating structure system combined with pontoon and semi-submersible type modules is proposed. This new system can reduce tensile forces of bottom slabs which could cause fatal damage of concrete floating structures. We performed a parametric study on the dimensions of this new system and investigate the sensitivity of the parameters to the behavior. In order to investigate various cases efficiently, we developed a simple two-step static analysis method for the fluid-structure interaction. An optimum system is derived from the investigation of the analysis results, weights and drafts of the hybrid structure. This study shows that introducing this new system to concrete floating structures is an effective way to reduce the tensile force of the bottm slab of such a floating structure. Also, it was found that when the length of the semi-submersible module is about 15%, the behavior would be optimal in the considered case.

• Journal of Korean Society of Steel Construction
• /
• v.23 no.6
• /
• pp.737-745
• /
• 2011

A concrete-filled tube is a concrete-filled steel tube structure. The steel tube confines the concrete to increase the compressive strength, and the concrete contains the buckling of the tube. CFT structures require a diaphragm to prevent buckling of steel at connections. An outer diaphragm has better concrete filling than a through diaphragm due to a large bore, but being larger than the through diagram, it has poorer constructability and cooperation with building equipment. In this study, a CFT structure that uses different types of diaphragms in its upper and lower connections to improve the concrete filling was tested and analyzed via the FEM program. The building structure had a floor slab that was unified with the upper diaphragm, so the outer diaphragm was placed at the upper bound. Moreover, the through diaphragm was placed at the lower connection to avoid obstruction from building equipment. The CFT structure with the improved concrete filling showed the same structural behavior as the CFT structure with the use of the same type of diaphragms at the upper and lower connections.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.9
• /
• pp.49-54
• /
• 2008

In this paper, the power added efficiency(PAE) of class F power amplifier is improved by applying a new Photonic Bandgap (PBG) structure on the output of amplifier. The proposed spiral PBG structure is a two-dimensional (2-D) periodic lattice patterned on a dielectric slab that does not require nonplanar fabrication process. This structure bas higher suppression performance at second harmonic. Also, It has a sharp skirt property. This new PBG structure can be applied with class F power amplifier for efficiency improvement. We obtained the PAE of 73.62 % for CDMA applications, and the PAE performance is improved as much as 6.2 % compared with that of a conventional class F power amplifier.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.4
• /
• pp.271-283
• /
• 2002

P-wave velocity of concrete is a crucial parameter in determining the thickness of concrete lining, the location of cracks or other defects in Impact-Echo(IE) method. This study introduces an IE-SASW method that may determine the P-wave velocity on a surface of each testing area using the Spectral Analysis of Surface Wave (SASW) method. In numerical studies(Part I), it was verified that P-wave velocities could be obtained from SASW. In this paper(Part II), experimental studies were made in slab type concrete model specimens in which voids and waterproof sheet were included at the known locations. Accordingly, the feasibility of the proposed method was evaluated. The IE-SASW method was also performed in the precast model tunnel on ground and open-cut tunnel in ground. SASW tests were performed to determine the P-wave velocity of the concrete and then IE tests were carried at regularly spaced points along the testing lines to determine the thickness of structures. The nondestructive testing method which combined SASW and IE tests showed the great potential in the field applications.

• Journal of Korean Society of Steel Construction
• /
• v.24 no.3
• /
• pp.313-323
• /
• 2012

The purpose of this study is to evaluate $CO_2$ reduction and the flexural performance of steel wire-integrated void deck plate slabs that were inserted in omega-shaped steel plates to reduce concrete and welded H-section beams. The void deck plate slab can secure the structure, not only reducing the weight of the building but it is also eco-friendly. Therefore, this study evaluated the flexural performance of the composite beam by conducting a monotonic loading test with the use of actuators. It quantitatively evaluated the $CO_2$ emission based on earlier studies. The main test parameters are the concrete thickness of upper slabs, and the interrupted width of the omega-shaped steel plate. The result of the test showed that the welded H-section beam applied steel wire-integrated void deck plate slabs that were inserted into the omega-shaped steel plate declined in flexural performance on the composite beam after reducing concrete volume. Likewise, it is effective in reducing $CO_2$.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.5 no.1
• /
• pp.1-12
• /
• 1985

This study is conserned for the optimum design of reinforced concrete slab-beam-column structures with multi-storys and multi-bays by Direct Method. Flexural and shear strength, sectional size, and steel ratio etc., were considered as the design-constraints and the cost function was taken as to objective function. They became high degree nonlinear problems. Using SLP as an analytical method of nonlinear optimal problems, an optimal algorithm was developed in this study and the algorithm was applied to the optimization of reinforced concrete structure system of 5 storys. The result converged to a optimal solution with 3 to 5 iterations, and proved that economical design could be possible when compared with conventional designs.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.4
• /
• pp.175-184
• /
• 2011

To take advantage of reduced on-site construction periods and minimize traffic impacts various types of steel grid composite deck have been developed since 1930's. Modular prefabricated unfilled grid decks permit a long-distance transportation and construction under unfavorable condition, for example, in mountainous regions due to its comparatively light-weighter structure than fully filled grid deck. In this study bending tests of unfilled grid decks for the deck member of various kinds of infrastructure are carried out, bending strength and behaviour of composite action are experimentally evaluated. In this bending test, design variables are considered, such as type of shear connection between steel grid and concrete slab, spacing between cross bars and thickness of concrete slab. Through test results bending strength and behaviour of composite action are evaluated, reference data for proper type of shear connection and other details of the deck, such as spacing between cross bars, are obtained.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.17-20
• /
• 2008

As a part of a research program to study the shear reinforcement of flat plate system, this investigation aimed to determine the effect of shear reinforcement type on punching shear strength of monolithic slab-column connection. A total of 5 specimens were fabrication and tested. The dimension of the slab were $2.63{\ast}2.725{\ast}0.18m$, with a centrally located column $0.6{\ast}0.8m$ in cross section. Experimental results showed that the CFS shear reinforcement was not effective because of lack of proper bond with concrete. 3 shear reinforcement except of CFS showed high effectiveness, which resulted in a considerable increment of the punching shear resistance of the connection.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.941-944
• /
• 2008

Various ductile fiber reinforced cement composite(DFRCC) including large quantities of PVA fiber or steel fiber have been developed recently and studies to find applications in diverse domains are currently conducted actively. Regard to economical efficiency, DFRCC becomes competitive when applied as special elements and repair material with small quantities rather than the casting of large volume for the main body of structures in field. The authors have developed FRP-DFRCC composite slab for bridges and a wet spraying repair technique using DFRCC. In case of the application on FRP-DFRCC composite slab, it was found that there was no problems the structure and durability of it after passed 3 months. And in case of the application on the application of the deteriorated sewage box that passed 20 years, it was found that there was no difference the repair performance between domestic PVA fiber and the Japan. Therefore, DFRCC using PVA fiber, the concrete structures can be increased to performance and secured the economical efficiency.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.11
• /
• pp.2603-2607
• /
• 2009

$LiNi_{0.5-x}Co_{2x}Mn_{0.5-x}O_{2}$ (x = 0, 0.1, 1/6, 1.2, 0.3) were synthesized by the solid-state reaction method. The crystal structure was analyzed by X-ray powder diffraction and Rietveld refinement. $LiNi_{0.5-x}Co_{2x}Mn_{0.5-x}O_{2}$ samples give single phases of hexagonal layered structures with a space group of R-3m for x = 0.1, 1/6, 0.2, and 0.3. The lattice constants of a and c-axis were decreased with the increase in Co contents in samples. The thickness of MO2 slab was decreased and inter-slab distance was increased with the increase in Co contents in $LiNi_{0.5-x}Co_{2x}Mn_{0.5-x}O_{2}$. According to XPS analysis, the valence states of Mn, Co, and Ni in the sample are mainly +4, +3, and +3, respectively. The discharge capacity of 202 mAh/g at 0.1C-rate in the potential range of 4.7 - 3.0 V was obtained in $LiNi_{0.3}Co_{0.4}Mn_{0.3}O_2$ sample, and $LiNi_{0.4}Co_{0.2}Mn_{0.4}O_2$ gives excellent cycle performance in the same potential range.