• Journal of Korea Water Resources Association
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• v.46 no.4
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• pp.327-334
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• 2013

In this study, the optimal slit length of perforated wall with single chamber below the still water level (SWL) is studied through the two dimensional test. The relationship between the reflection coefficient and the shape of structures such as chamber width(B) and slit length(S) are investigated by applying the various wave conditions. The random waves were used for the test by using Bretschneider-Mitsuyasu frequency spectrum. Minimum reflection coefficient is obtained at $B/L_s{\approx}0.15$ condition, this result is different from the regular wave condition. Also the minimum reflection coefficients are measured at $S/H_s{\approx}2.5$. This means that the optimal slit length below the still water level is 2.5 times of the incident wave height.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.190-198
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• 2018

The Epoxy-coated Reinforcing bars have been proved to be able to extend a durability life because of its excellent corrosion resistance in bridges and structures under marine and severe environments. The usage of epoxy-coated reinforcement is continuously increasing in developed countries such as the US and Japan. However, domestic use is extremely limited due to lack of research and development, poor production facilities, low quality, increase of initial costs, and difficulty of field management. This study suggests the improvement of construction quality management such as manufacturing, transportation and construction for the field application through the test construction of the proven product in the related test results of the epoxy coated steel bars produced in the recently improved manufacturing facility.

• Journal of the Korean GEO-environmental Society
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• v.17 no.6
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• pp.5-12
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• 2016

This paper deals with the result of thermal resistance test with backfill materials as bottom ash by using backfill material. Bottom ash, one of coal ashes, can be reused to replace sand because of its similar engineering properties. But without considering the thermal property, the abuse of bottom ash resulted in damage for existing structures. To investigate the thermal conductivity of bottom ash, laboratory tests for thermal resistance of that were carried out in this study. Thermal properties of bottom ash was compared with those of in-situ soil, sand, backfill material which can be applied as filling material. The tests were classified by water contents defined as the major influence factor. The beneficial use method of bottom ash was suggested as backfilling material.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.525-528
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• 2008

For well-constructed concrete, its service life is a long term and it has an enough durability performance. However, for cracked concrete, it is clear that cracks should be preferential channel for the penetration of aggressive substance such as chloride ions according to author's previous researches. In order to enhance the lifetime of cracked concrete, critical issues in the performance of the concrete is the risk of chloride-induced corrosion. Even though crack width can be reduced due to the high reinforcement ratio, the question is to which extend these cracks may jeopardize the durability of cracked concrete. If the size of crack is small, surface treatment system can be considered as one of the best options to extend the service life of concrete structures exposed to marine environment simply in terms of cost effectiveness versus durability performance. Thus, it should be decided to undertake an experimental study on the effect of different types of surface treatment system, which are expected to seal the concrete and the cracks to chloride-induced corrosion in particular. In this study, it is examined the effect of surfaced treated systems on chloride penetration through microcracks. Single surface treatments of penetrant or coating and double application were considered as an experimental variation. RCM (Rapid Chloride Migration) testing is accomplished to visualize chloride penetration via cracks.

• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.474-483
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• 2016

Accidental events such as collisions, groundings, and hydrocarbon explosions in marine structures can cause catastrophic damage. Thus, it is extremely important to predict the extent of such damage, which determines the total amount of oil spills and the residual hull girder strength. Punching fracture tests were conducted by Choung (2009b), where various sizes of indenters and circular unstiffened steel plates with different thicknesses were used to quasi-statically realize damage extents. A three-dimensional fracture strain surface was developed based on a reference (Choung et al., 2015b), where the average stress triaxiality and average normalized Lode angle were used as the parameters governing the fracture of ductile steels. In this study, new numerical analyses were performed using very fine axisymmetric elements in combination with an Abaqus user-subroutine to implement the three-dimensional fracture strain surface. Conventional numerical analyses were also conducted for the tests to identify the best fit fracture strain values by changing the fracture strains. Based on the phenomenon of the average normalized Lode angle starting out positive and then becoming slightly negative, it was inferred that the shear stress primarily dominates in determining the fractures locations, with a partial contribution from the compressive stress. It should be stated that the three-dimensional fracture surface effectively predicted at least the shear stress-dominant fracture behavior of a mild steel.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.729-737
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• 2008

As increasing demand on marine structures and skyscrapers, a deep shaft pile foundation is more to be used for the place having weak ground strength. Because heavy horizontal force is generally applied on upper part of pile foundation used in civil or architectural construction, steel pile is largely used with its high resistance to shear force and bending moment, and its capability to carry heavy loads. The steel pile has advantage in good constructibility, high applicability on site and easy handing, but has disadvantage in cost, more expensive than other material pile. This study is about the Composite pile that makes economical construction possible by reducing material cost of pile; using steel and PHC pile simultaneously while preserving the advantage of steel pile that large resistance to horizontal force and bending moment. A Non Welding connection method is applied to this composite pile and this method could reduce the cost and period of construction and could increase the quality of construction by solving the problem of current welding method and by improving the workability of pile connection. In this study, characteristics of driveability of non welding composite pile is analyzed prior to main project while the purpose of main project is proving the applicability of Non Welding Composite Pile by conducting various kind of loading test to analyze the characteristics behaviour of Non Welding Composit Pile and by verifying stability of non welding connection pile.

• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.179-183
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• 2005

The High-tensile steel has been recognized as a promising concept for structural design of light weight transportation systems such as aircraft high speed trains and fast ships. Using the high-tensile steel has been widely used in ship structures, and this enables to reduce the plate thickness. Using the high-tensile steel effectively for a ship hull, the plate thickness becomes thin so that plate buckling may take place. Therefore, precise assessment of the behavior of plate above primary buckling load is important. In this study, examined closely secondary buckling behavior after initial buckling of thin plate structure which operated compressive load according to the various kinds of yield stress with simply supported boundary condition. Analysis method is F.E.M by commercial program(ANSYS V7.1) and complicated nonlinear behaviour can analyze using art-length method about secondary buckling.

• Smart Structures and Systems
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• v.26 no.3
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• pp.331-343
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• 2020

In this paper, based on the CPT, motion equations for a sandwich plate containing a core and two integrated face-sheets have derived. The structure rests on the Visco-Pasternak foundation, which includes normal and shear modules. The piezo-magnetic core is made of CoFe₂O₄ and also is subjected to 3D magnetic potential. Two face sheets at top and bottom of the core are under electrical fields. Also, in order to obtain more accuracy, the effect of flexoelectricity has took into account at face sheets' relations in this work. Flexoelectricity is a property of all insulators whereby they polarize when subject to an inhomogeneous deformation. This property plays a crucial role in small-scale rather than macro scale. Employing CPT, Hamilton's principle, flexoelectricity considerations, the governing equations are derived and then solved analytically. By present work a detailed numerical study is obtained based on Piezoelectricity, Flexoelectricity and modified couple stress theories to indicate the significant effect of length scale parameter, shear correction factor, aspect and thickness ratios and boundary conditions on natural frequency of sandwich plates. Also, the figures show that there is an excellent agreement between present study and previous researches. These finding can be used for automotive industries, aircrafts, marine vessels and building industries.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.6
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• pp.379-389
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• 2016

This study intends to evaluate the conservativeness of the fixed-base analysis as compared to the soil-structure interaction (SSI) analysis for the seismically isolated model of a nuclear power plant in Korea. To that goal, the boundary reaction method (BRM), combining frequency-domain and time-domain analyses in a twofold process, is adopted for the SSI analysis considering the nonlinearity of the seismic base isolation. The program KIESSI-3D is used for computing the reaction forces in the frequency domain and the program MIDAS/Civil is applied for the nonlinear time-domain analysis. The BRM numerical model is verified by comparing the results of the frequency-domain analysis and time-domain analysis for the soil-structure system with an equivalent linear base isolation model. Moreover, the displacement response of the base isolation and the horizontal response at the top of the structure obtained by the nonlinear SSI analysis using BRM are compared with those obtained by the fixed-base analysis. The comparison reveals that the fixed-base analysis provides conservative peak deformation for the base isolation but is not particularly conservative in term of the floor response spectrum of the superstructure.

• Molecules and Cells
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• v.38 no.12
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• pp.1086-1095
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• 2015

The psychrophilic organism Colwellia psychrerythraea strain 34H produces extracellular polysaccharide substances to tolerate cold environments. Sedoheptulose 7-phosphate isomerase (GmhA) is essential for producing $\small{D}$-glycero-$\small{D}$-mannoheptose 7-phosphate, a key mediator in the lipopolysaccharide biosynthetic pathway. We determined the crystal structure of GmhA from C. psychrerythraea strain 34H (CpsGmhA, UniProtKB code: Q47VU0) at a resolution of $2.8{\AA}$. The tetrameric structure is similar to that of homologous GmhA structures. Interestingly, one of the catalytic residues, glutamate, which has been reported to be critical for the activity of other homologous GmhA enzymes, is replaced by a glutamine residue in the CpsGmhA protein. We also found differences in the conformations of several other catalytic residues. Extensive structural and sequence analyses reveal that CpsGmhA shows high similarity to Escherichia coli DnaA initiatorassociating protein A (DiaA). Therefore, the CpsGmhA structure reported here may provide insight into the structural and functional correlations between GmhA and DiaA among specific microorganisms.