• Journal of Environmental Science International
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• v.7 no.3
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• pp.335-348
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• 1998

The intensive meteorological observations including pibal balloon at Ungcheon, airsonde and 10m meteorological tower observations at Gulup-Do, where are located In the western coastal region, are taken to Investigate the characteristics of the upper and lower atmospheric structure and the local circulation pattern during the period of 17 to 22 September 1996. The diurnal variations of weather elements(i.e. air temperature, humidity, pressure, and Und speeds at Gulup-Do are analyzed and discussed with those at four inland meteorological stations. The vertical profiles of wind vector, ortho- gonality(Ω), and shear obtained from the pibal obsenrations are also presented to examine the change of wand structure according to the synoptic-scale pressure system's movement. The diurnal temperature changes at Gulup-Do are more sensitive than that of Inland meteorological stations In case of the mow of southwesterlies but are not dominant due to the ocean effect under the Influence of relatively cold northerlies. A well defined mixed layer Is developed from the 500m to the maximum 1700m with a significant capping Inversion layer on the top of it. It can be found from the vertical profiles of wind vector that the wind become generally strong at the interface heights between cloud lay- ers and non-cloud layers. The maximum Und shear Is appeared at the bel각t where the varlauon of wand direction Induced by the passage of synoptic-scale pressure system Is accompanied with the In- crease of Und speed. Based on the wind orthogonality, the change of wind direction with height is more complicated In cloudy day than In clear day. In case of a fair weather, the change of wand direction is showed to be at around 2km.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.51-59
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• 2006

The surface wave data obtained in a tidal flat located in the sw coast of the Korean Peninsula were used to analyse the shear wave velocity structure of the area. First, the phase velocity dispersion curves were obtained by the tau-p stacking method and the group velocity dispersion curves by a wavelet transform method and the Multiple Filtering Technique by Dziewonski. The phase velocity dispersion curves exhibited bigger errors than the group velocity curves. The results showed that the wavelet transform method was more effective in separating the fundamental and the 1st higher mode group velocity curves than the Multiple Filtering Technique. Combined use of the fundamental and the 1st higher mode group velocity dispersion curves in the inversion for the shear wave velocity structure gave better spatial resolution compared when the fundamental mode group velocity was used alone. This study indicates that the group velocity dispersion curves can be used in the inversion of Rayleigh waves for the shear wave velocity structure, especially effectively with the higher mode group velocity curves together.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.255-264
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• 2015

Steel plate concrete (SC) structure has been developed as a new structural type. Rational damping value shall be determined for the seismic design of SC structure. This study evaluated damping ratio of SC structure through experiments. For the study, a SC shear wall specimen was constructed and dynamically tested on the shaking table. Acceleration time history responses measured from testing were converted to the transfer functions and analyzed by using experimental modal analysis technique. The structural damping ratio of the specimen was identified as 4% to critical. Considering the shaking table test was performed at the excitation level corresponding to the low stress level of the specimen, 4% could be suggested as a structural damping for design of SC structure for operating basis earthquake.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.81-89
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• 2015

This study takes shear wall of reinforced concrete structure as study object, and the purpose of this study is to suggest structure BIM based on automatic reinforcing bar placement system applying set-based design through the most optimum reinforcing bar placement group that was selected by applying AHP (analytical hierarchy process) method from design step. For this, the most optimum reinforcing bar placement group was selected by pairwise comparison analysis on complex standard of multiple alternatives. And shear wall automatic reinforcing bar placement system has been developed, which can automatically generate members and arrange reinforcing bar by structure design algorithm and using open API (application programming interface) provided by a BIM software vendor. As a result, the most optimum reinforcing bar placement group of the highest weight, ALT1, was selected and was generated using Tekla Structure program.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.348-355
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• 2000

The characteristics on non linear behavior and the failure mechanism of RC space frame structure serving railway under seismic action have been investigated by numerical analysis in time domain. The structure concerned is modeled in 3 dimensional extent and RC frame elements with fibers are employed. Fibers are characterized as RC one and PL one to distinguish different energy release after cracking. Due to deviation of mass center and stiffness center of entire structure the complex behavior under seismic action is shown. The excessive shear force is concentrated on the pier beside flexible one relatively, which leads to failure of bridge concerned.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.677-684
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• 2007

This study investigates the failure mechanism of RC beams strengthened with GFRP (glass fiber reinforced polymer) sheets. After analyzing failure mechanisms, the various methods to prevent the debonding failures, such as increasing bonded length of GFRP sheets, U-shape wrappings and epoxy shear keys are examined. The bonded length of GFRP sheets are calculated based on the assumed bond strengths of epoxy resin. The U-shape wrappings are either adopted at the end or center of the CFRP sheets bonded to the beam soft. The epoxy shear keys are embedded to the beam soft to provide sufficient bond strength. The end U-wrappings and the center U-wrappings are conventional, while epoxy shear keys are new details developed in this study. A total six half-scale RC beams have been constructed and tested to investigate the effectiveness of each methods to prevent debonding failure of GFRP sheets. From the experimental results, it was found that increasing bonded length or end U-wrappings do not prevent debonding failure. On the other hand, the beams with center U-wrappings and shear keys reached an ultimate state with their sufficient performance. The center U-wrappings tended to control debonding of the longitudinal GFRP sheets because the growth of the longitudinal cracks along the edges of the composites was delayed. In the case of shear keys, it was sufficient to prevent debonding and the beam was failed by GFRP sheets rupture.

• Proceedings of the Korean Fiber Society Conference
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• 1990.06b
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• pp.36-37
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• 1990

In the past, facile dissolution of cellulose has been hampered by the lack of suitable nondegrading solvents. Recently, this problem has been solved in our laboratory by the discovery of an inexpensive, convenient solvent system, that is the mixture of $NH_3\;and\;NH_4SCN$, for cellulose. Also, the $cellulose/NH_3/NH_4SCN$ solution system has been found to form the anisotropic, i.e., liquid crystalline phase. It is believed that both the cholesterio and the nematic phase occur. This finding has prompted extensive on-going researoh on the formation of the liquid crystalline phase from an inexpensive natural source such as cellulose since the nematic phase is envisioned as an excellent precursor sources for products with desirable properties, for example, high modulus and high strength. This interest naturally leads to a desire to understand the theological properties of the nematic phase so that the transformation of the nematic phase to the solid state with desirable properties can be efficiently accomplished, ;From this point of view, the theological behavior of the $cellulose/NH3_/NH_4SCN$ system has been studied as a function of shear rate and shear stress over a wide range of solvent compositions, cellulose concentration, centrifugation and urea contents, Results indicate that the viscosity decreases with increasing shear rate. A marked shear thinning behavior and a quasi-Newtonian behavior were observed in the low shear rate region and in the high shear rate region, respectively for all solvent compositions. The $cellulose/NH_3/NH_4SCN$ solution system only exhibited the viscosity increase with increasing cellulose concentration and failed to show the viscosity drop generally observed at the point of incipience of liquid crystal formation, This may be due to the gel-like nature of the solution by the association of the rodlike molecules into bundles which may serve as crosslinking points giving the cellulose solution a network structure. Also, simply hydrogen bonding may be so restrictive of molecular mobility that a viscosity drop is blocked. In addition to the above results, yield stress and thixotropy were also observed in the $cellulose/NH_3/NB_4SCN$ solution system which are characteristics of liquid crystal and gel, The results of the effect of centrifugation on viscosity show that viscosity decreases by the application of centrifugation. This may be explained by the change of the piled polydomain structure to the dispersed polydomain structure due to the pressure gradient generated during centrifugation.ation.

• Steel and Composite Structures
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• v.37 no.3
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• pp.323-339
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• 2020

In steel framed-tube structures (SFTSs), the plastic hinges at beam-ends cannot be adequately improved because of the large cross sections of spandrel beams, which results in the lower ductility and energy dissipation capacities of traditional SFTSs. To address this drawback, high-strength steel fabricated SFTSs with bolted web-connected replaceable shear links (HSFTS-SLs) have been proposed. In this system, shear links use conventional steel and are placed in the middle of the deep spandrel beams to act as energy dissipative components. In this study, 2/3-scaled HSFTS-SL specimens were fabricated, and cyclic loading tests were carried out to study the seismic performance of both specimens. The finite element models (FEMs) of the two specimens were established and the numerical results were compared with the test results. The results showed that the specimens had good ductility and energy dissipation capacities due to the reliable deformation capacities. The specimens presented the expected failure modes. Using a shorter shear link can provide a higher load-carrying capacity and initial elastic lateral stiffness but induces lower ductility and energy dissipation capacity in HSFTS-SLs. The performance of the specimens was comparable to that of the original sub-structure specimens after replacing shear links. Additionally, the expected post-earthquake recoverability and resilience of the structures could be achieved by replacing shear links. The acceptable residual interstory drift that allows for easy replacement of the bolted web-connected shear link was 0.23%. The bolted web-connected shear links had reliable hysteretic responses and deformation capacities. The connection rotation had a notable contribution to total link rotation. The results of the numerical analysis run for the proposed FEMs were consistent with the test results. It showed that the proposed FEMs could be used to investigate the seismic performance of the HSFTS-SL.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.60-68
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• 2017

This study was made to examine the motion characteristics according to the reinforcement of the reinforcement length and stiffener reinforcement for shear reinforcement to the foundation structure reinforced with shear reinforcement steel plate. Experimental study was made after specimen was installed on the ground as the same as in the practical site. Reinforcement lengths of the steel for shear reinforcement are divided into 1,000 mm, 1,200 mm and 1,400 mm in the specimen and as for reinforcement method of the stiffener, 4 stiffeners with interval of 100mm reinforced with the same materials as the shear reinforcement were manufactured for the experiment. Considering result of the experiment, it is expressed that no effect of the stiffener reinforcement was found and regarding the reinforcement length of shear reinforcement material the crossed point of the two converted lines of the value that the shear force is expressed in the bearing power in the expanded dangerous section and the value that the shear capacity receivable by the reinforcement materials in the dangerous section is proposed as effective reinforcement length.

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