• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.29-32
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• 2009

Building foundations for Top-Down construction require a special setting, because the foundations have to be placed way before excavation for the substructure of main building, Usually, the foundation goes into the layer of rock and it is often called rock-pier foundation, Currently, a cage of steel reinforcing bars is inserted to the pre-excavated hole in the rock layer, hanging down from the wide flange steel column above. This paper presents a new method for connecting the prefounded column and the steel cage with a coupler for better connection between the two, The use of a circular Concrete Filled Tube (CFT) as a prefounded column makes it possible to have this type of connection. The details of the connection and application to a Top-Down construction site is also included in this paper.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.79-80
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• 2022

A method for repairing cracks using low-viscosity resins has been proposed as a construction method that can quickly repair roads from deterioration. However, when the viscosity of the epoxy resin is high, there is a limit in that it is difficult for the material to penetrate into microcracks and cracks in the concrete top plate. In this study, an epoxy thin-layer pavement repair method was developed using low-viscosity PMMA (Poly methyl methacrylate) to repair microcracks on the pavement surface and pavement layer and reinforce the pavement surface. Materials necessary for the thin-layer packaging method were developed, and performance was evaluated to meet the epoxy binder quality standards. As a result, all materials met the required performance.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.309-309
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• 2006

Latest developments on hybrid nanostructured materials fabricated by applying self-assembly strategies on organic/inorganic nanotemplates are discussed. Within this frame, numerous functional nanomaterials including arrays of composite metal/semiconductor nanoparticles, planar waveguides and functional multilayer thin films are generated using self-assembled polymers as templates or building blocks. In particular, surface plasmon resonance based optical sensing is employed to investigate nanofabrication processes occurring in nanoscale dimention. We also suggest unprecedented pathways to hybrid supramolecular multilayer nanoarchitectures in 1D or 2D geometry via layer-by-layer self-assembly.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.85-86
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• 2023

This study confirmed the improvement of the Composite Waterproof Method in which the sheet layer is partially attached with perforated film and the joint is FRP-treated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.85-86
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• 2023

In this study, charring properties such as charring layer and mass change of wood with temperature were investigated through cone calorimeter test on douglas-fir, which is representative of various wood structures. the results showed that ignitions at 390 degrees and a charring layer is formed.

• Geomechanics and Engineering
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• v.32 no.3
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• pp.245-254
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• 2023

Through qualitative analysis and quantitative analysis, the contradictory conclusions about the stability of the settled goaf with two-layer coal seams subject to building load were obtained. Therefore, it is necessary to combine the additional stress method and numerical simulation to further analyze the foundation stability. Through borehole analysis and empirical formula analogy, the height of water-conducting fracture zone in No.4 coal and No.9 coal were obtained, providing the calculation range of water-conducting fracture zone for numerical simulation. To ensure the accuracy of the elastic modulus of broken gangue, the stress-strain curve were obtained by broken gangue compression test in dried state of No.4 coal seam and in soaking state of No.9 coal seam. To ensure the rationality of the numerical simulation results, the actual measured subsidence data were retrieved by numerical simulation. FISH language was used to analyze the maximum building load on the surface and determine the influence depth of building load on the foundation. The critical building load was 0.16 MPa of No.4 settled goaf and was 1.6 MPa of No.9 settled goaf. The additional stress affected the water-conducting fracture zone obviously, resulted in the subsidence of water-conducting fracture zone was greater than that of bending subsidence zone. In this paper, the additional stress method was analyzed by numerical simulation method, which can provide a new analysis method for the treatment and utilization of the settled goaf.

• Membrane and Water Treatment
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• v.10 no.3
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• pp.245-250
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• 2019

Prussian blue (PB) is well known for its excellent $Cs^+$ ions adsorption capacity. Due to the high dispersibility of PB in aqueous phase, composite materials imbedding PB in supporting materials have been introduced as a solution. However, building PB particles inside porous supporting materials is still difficult, as PB particles are not fully formed and elute out to water. In this study, we suggest layer-by-layer (LBL) assembly to provide better immobilization of PB on supporting materials of poly vinyl alcohol sponge (PVA) and cellulose filter (CF). Three different PB attachment methods, ex-situ/in-situ/LBL assembly, were evaluated using PB leaching test as well as $Cs^+$ adsorption test. Changes of surface functionality and morphology during PB composite preparation protocols were monitored through Fourier transform infrared spectroscopy and scanning electron microscopy. The results indicate that LBL assembly led to better PB attachment on supporting materials, bringing less eluting PB particles in aqueous phase compared to other synthesis methodologies, such as ex-situ and in-situ synthesis. By enhancing the stability of the adsorbent, adsorption capacity of PVA-PB with LBL improved nine times and that of CF-PB improved over 20 times. Therefore, the results suggest that LBL assembly offers a better orientation for growing PB particles on porous supporting materials.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.200-201
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• 2021

According to the dispute cases filed for claiming the collective defect repair fees, inter-layer concrete joints turned out to be the most frequently disputed item. For this reason, this study selects the inter-layer concrete joints to further analyze the primary causes and details of each dispute case. From the results of this study, three primary causes of the disputes are found, which are 1) the absence of standard specifications for construction quality control and management after construction; 2) the absence of established standards for repair when construction defects are found. In order to prevent construction defects in inter-layer concrete joints, this study provides three suggestions including 1) the current standard specifications for inter-layer concrete joints should be further specified by the Ministry of Land, Infrastructure and Transport; 2) a construction defect should be judged according to the compliance to the standard specifications; and 3) a clear and institutional protocol needs to be established for defect repair in cases that new public apartment houses have been judged to have defects.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.107-115
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• 2014

In this study, we examined the seismic isolation effects due to the difference between the center of mass of the building and the center of stiffness of isolation layer. Because the base isolation technique is a technique that is highly dependent on the performance of seismic isolation devices installed on the seismic isolation layer, we have to examine the horizontal stiffness of seismic isolation devices after making them. If difference between the design stiffness and the actual stiffness of the seismic isolation device occurred, a big problem may be generated in the upper members on the seismic isolation layer. The analytical results show that the more eccentricity increases, the more maximum response acceleration, story shear and the member forces of the upper part of the structure increases, and the damage is expected to be in excess. Therefore, it is recommended that if possible, isolation devices have to be designed to coincide the center of mass of the building with the center of stiffness of isolation layer. If not after making isolation devices, they need to be relocated to prevent the eccentricity.

• Tunnel and Underground Space
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• v.25 no.4
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• pp.383-396
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• 2015

It is analyzed the risk of building damage due to ground surface subsidence occurred during constructing a tunnel below buildings in sand-gravel layer. The overburden and the thickness of sand-gravel layer is about 20m and the width and the height of the tunnel are 12m and 8.6m, respectively. The tunnel is pre-reinforced by umbrella method with three rows of long steel pipes and grouting. Surface subsidence is measured at 36 points surrounding buildings and measured data are used to calculate optimized three dimensional subsidence surface. Depending on the building location, deflection ratio and horizontal strain are calculated to evaluate the risk of building damage. No damage occurs at the buildings because of both the small deflection ratios involved 1~4mm subsidence and compressive horizontal strains.