• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.181-188
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• 2000

This study deals with the method of test for waterproof agent and admixture of cement, and especially, the effect in bond strength between waterproofing layer and mortar of concrete substrate in building construction. The purpose of this study is that it makes the estimation value of bond strength of concrete wall and anticorrosive when coated waterproof agent and admixture of cement as waterproofing materials for durability performance estimation depend on concrete watertighness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.185-188
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• 2002

An abrasive vitreous bonded solid mass having a vitrified abrasive structure comprising diamond grains which are held by an in inorganic bonding agent, the vitrified diamond wheel is impregnated with a composition which comprises a thermosetting synthetic resin and a surfactant. The vitrified diamond wheel is manufactured by preparing the composition including the resin and the surfactant, impregnating the abrasive structure with the composition, and curing the composition. The diamond wheel newly developed showed excellent performance in grinding carbide.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.04a
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• pp.185-188
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• 2005

This paper suggests a control method for efficient topology/parameter evolution in a bond-graph-based GP design framework that automatically synthesizes designs for multi-domain, lumped parameter dynamic systems, We adopt a hierarchical breeding control mechanism with fitness-level-dependent differences to obtain better balancing of topology/parameter search - biased toward topological changes at low fitness levels, and toward parameter changes at high fitness levels. As a testbed for this approach, an eigenvalue assignment problem, which is to find bond graph models exhibiting minimal distance errors from target sets of eigenvalues, was tested and showed improved performance for various sets of eigenvalues.

• Journal of The Korean Digital Architecture Interior Association
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• v.12 no.3
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• pp.59-66
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• 2012

Autoclaved Lightweight Concrete(ALC) features such as a high performance insulation, the fire resistance, the advantage of easy handing construction, and lightweight panels applied the curtain wall system. ALC materials are certified as non-toxic environmental and eco-friendly productions. But ALC external panels mixed with blast furnace slag pounder and silica fume have to be coated with a stucco compound or plaster because of resisting the ambient environment. This study is that mixing tests to evaluate a performance analysis of exterior paints to be make-up pigments(organic or inorganic) coated with panel surface. Testing compared by KS F 2476; flow test, KS F 2426; compression strength test, KS F 2762; bond strength test. In results, the case of the inorganic binder, ratio of alumina cement : anhydrite is 90:10 to 80:20 at the highest level of intensity. In the case of the organic binder, adhesive strength rating at surface of ALC, the pullout strength is below 0.5 $N/mm^2$ but the normal concrete is over 2.0$N/mm^2$. A contents ratio of EVA resin is more than 3% and then bond strength is effectively.

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.99-108
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• 2012

Ultra High Performance Concrete(UHPC) has compressive strength higher than 180 MPa. The use of steel fibers in the dense UHPC matrix increases tensile strength, ductility and bond strength between UHPC and rebars. However, to apply the advance material behavior of UHPC to the design of a structure, we need design formulas. The crack formula is one of them. This paper investigated experimentally the bond behavior of a rebar and K-UHPC, the UHPC developed by Korea Institute of Construction Technology, and, modified CEB-FIP crack formula based on the test. In addition, this paper tested the crack behavior of K-UHPC reinforced with rebars to verify the modified crack formula. The result showed that the modified formula is reasonable to predict the width of cracks in the reinforced K-UHPC structures.

• Computers and Concrete
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• v.24 no.1
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• pp.37-49
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• 2019

In this study, the shear behaviour of reinforced concrete (RC) beams that were retrofitted using precast panels of ultra-high performance fiber reinforced concrete (UHPFRC) is presented. The precast UHPFRC panels were glued to the side surfaces of RC beams using epoxy adhesive in two different configurations: (i) retrofitting two sides, and (ii) retrofitting three sides. Experimental tests on the adhesive bond were conducted to estimate the bond capacity between the UHPFRC and normal concrete. All the specimens were tested in shear under varying levels of shear span-to-depth ratio (a/d=1.0; 1.5). For both types of configuration, the retrofitted specimens exhibited a significant improvement in terms of stiffness, load carrying capacity and failure mode. In addition, the UHPFRC retrofitting panels glued in three-sides shifted the failure from brittle shear to a more ductile flexural failure with enhancing the shear capacity up to 70%. This was more noticeable in beams that were tested with a/d=1.5. An approach for the approximation of the failure capacity of the retrofitted RC beams was evolved using a multi-level regression of the data obtained from the experimental work. The predicted values of strength have been validated by comparing them with the available test data. In addition, a 3-D finite element model (FEM) was developed to estimate the failure load and overall behaviour of the retrofitted beams. The FEM of the retrofitted beams was conducted using the non-linear finite element software ABAQUS.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.181-182
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• 2020

In this study, oxidized graphene nanoplatelet(GO) was prepared by oxidizing graphene nanoplatelet(GNP) with nitric acid in order to solve the problem of dispersion of GNP, one of nano materials. GNP/Epoxy and GO/Epoxy were prepared by mixing GNP, GO with 0.1, 0.3, 0.5 and 1.0 wt.% in epoxy and the mechanical properties, bond performance were evaluated. As a result, GNP/Epoxy and GO/Epoxy showed higher tensile strength than Neat Epoxy at the 0.1, 0.3 wt.%. Especially, when 0.1 wt.% of GO was incorporated into epoxy resin, it showed highest tensile strength. It was confirmed that acid treatment of GNP was effective in improving the mechanical properties of epoxy paint. However, graphene material was found that it was not effective in improving the bond strength of the epoxy paint.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.987-990
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• 2007

Warranty contracting is contracting methods that European Countries have applied to asphalt pavement projects from long ago, and in America as the expected effects of the warranty contracting are being verified to introduce it, the number of projects with warranty is being increased rapidly. In Japan, the warranty contracting suitable for Japanese style was established and is being applied. This study investigated and analyzed the present state of the warranty contracting being applied to European countries, America and Japan, and suggested advantages and disadvantages in introducing the warranty contracting into Korea and directions to introduce it. The principal result of this study is that performance bond contract system, performance surety bond system and performance bidding system should be established to introduce the warranty contracting into Korea.

• Korean Journal of Construction Engineering and Management
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• v.9 no.4
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• pp.66-74
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• 2008

Warranty contracting for pavements construction has been widely used in Europeans countries, Japan, and the U.S. and the benefits of warranty contract has been proven. This research investigated the European, U.S., and Japanese warranty contract policies and compared pros and cons. The most appropriate warranty contract policy solution is developed to fit in the Korean construction industry culture. Three main conclusions have been developed in this study: (1) performance specifications should be developed; (2) the systematic method is required to estimate the appropriate costs of performance bond and warranty period, etc.; and (3) short and long term plans for adopting performance warranty contract in Korea are suggested.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.176-181
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• 2018

Concrete structures are degraded physically and chemically due to various reasons after construction. Because the deterioration of concrete structure reduces the service life, reasonable repair and maintenance techniques are needed. Recently, in order to efficiently repair concrete structures, many researches on hybrid repair materials having improved adhesion performance have been carried out actively. In this study, we developed a hybrid repair material containing rapid hardening cement, PVA powder, nylon fiber, and latex to improve adhesion and water-tightness of existing concrete. The compressive strength, drying shrinkage and the adhesion strength test were carried out to evaluate the performance of the repair material. In addition, the flexure bond performance was evaluated before and after repair. From the results, the bending strength was 110% ~ 150% in all specimens except for the specimen containing only the rapid hardening cement, and all the specimens behaved with the existing concrete in the crack pattern generated by the bending strength.