• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.117-123
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• 2013

As fiber reinforced polymer (FRP) material is appled for a curved structure such as tunnel, FRP material must has a curved shape. Until now, the curved FRP material has been producted by hand-lay-up or filament winding work. It is impossible for mass production of the curved FRP material by these methods. Also, the quality of product by these methods is lower than that by pultrusion method. New pultrusion method and equipment had been developed for production of FRP material with steady curvature. The objective of this study is to evaluate the effect of freezing and thawing on adhesion of cement concrete with coarse-sand coated FRP in repair and reinforcement of cement-concrete structure using curved FRP material.

• Journal of the Korea Institute of Building Construction
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• v.17 no.4
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• pp.341-348
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• 2017

The performance degradation of concrete pavement by winter deicer is very serious in Korea, and its maintenance and rehabilitation brings a high expense. Therefore, a suitable method for rehabilitation of such concrete pavement and repair material of proper performance are required. In this study, the properties of compressive strength, ability to resist chloride ion penetration, and properties of dry shrinkage of magnesium phosphate ceramics were assessed to evaluate its applicability as a repair material for concrete pavement in Korea. As a result, the mortar flow showed a normal level of 190 mm, but the viscosity was high and the self-flow ability was poor. The setting time was 12 minutes, leading very rapid-hardening, and thus a prompt work was required. The compressive strength of mortar was 38.4MPa in 2 hours, 73.8MPa in 24 hours, and 111.0MPa in 28 days, showing a significant level. As a result of the test to chloride ion penetration resistance, mortar showed 143 Coulombs, and concrete showed 172.6 Coulombs, which fell under very low level. The drying shrinkage of MPC concrete in 40 days was below $60{\times}10-6$, and comparing with normal cement concrete, it showed the level below 1/10 of other concrete to secure an excellent volume stability. As above, magnesium phosphate ceramics has excellent strength performance, chloride ion penetration resistance, and volume stability, and this in the future shall be used in construction under the consideration of working time or workability, requiring further improvement for such performance.

• Journal of the Korea Safety Management & Science
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• v.22 no.3
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• pp.1-8
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• 2020

The desulfurizers facility is cylindrical shape. To operate properly it needs nozzles cleaned, get rid of lime adhesion and sludge, repair the wear and corrosion of facility regularly. For this purpose, workers shall access the ceiling or vertical wall at high place. Ordinary scaffoldings such as steel pipe scaffolding or system scaffolding have been using so that workers can access them. With these ordinary scaffoldings, openings around cylindrical wall are inevitable which make workers can expose always to the risk of falling. The purpose of this study is to develop customized scaffolding to minimize the openings to prevent workers form falling during maintenance it. It consists of a hexagonal central tower and six trapezoidal outer towers. And the bracing among the towers have connected each other for self-standing and for maintaining the structure of towers. Span decks, the circumference footstools, steps, etc. are laid on each floor. The safety is reviewed by structural analysis and performance test. With this study, openings each floor of this scaffold are removed. The gap between the cylindrical wall and the edge of the work stage is approximately 100 mm. Therefore, we expect that workers can work safely and efficiently.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.136-149
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• 2011

Large portion of the domestic bridges are slab bridges reflecting the geographical characteristic of the country, where exists lots of inclines and small winding brooks. Many of the slab bridges are damaged and superannuated as they become obsolete. Deterioration is accelerated when the traffic density becomes large and heavy vehicles pass frequently. A strengthening method for deteriorated slab bridges was studied in this work. The examined net-type strengthening method uses both longitudinal and transverse prestressing for strengthening. In this way, the deflection at the center of the slab can be better controlled, and consequently, the slab is more efficiently strengthened. Three slab specimens were fabricated for the experimental test and subjected to three different loading conditions, and the load bearing capacities and deflections of slabs were examined. Flexural stiffness of slabs increased by 30.7~107.3%, and deflection of slabs decreased by 27.6~52.2% after net-type strengthening. The net-type prestressing is efficient to the strengthening for the center of a slab, and its efficiency is also valid under eccentric loadings. Since extra prestress forces can be added in the future, if necessary, the net-type strengthening system is advantagous for the maintenance and repair of slab bridges.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.3
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• pp.411-417
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• 2018

This paper proposes and implements an on-line instruction manual system which can generate the instruction manual page for the target device at the smartphone on the spot. The instruction manual app. on smartphone scans a QR code or reads NFC tag attached in the instruction manual management module embedded in the target device, and receives instruction manual data from the instruction manual management module through the Bluetooth communications and finally shows the refined instruction manual pages on the smartphone display using a Web-based templates. For the evaluation we embedded the instruction manual management module for an industrial generator with its instruction manual data. Assuming a circumstance of blackout we show that the proposed system can reduce the repair work within two steps compared to three steps in the existing one without the proposed system.

• Advances in materials Research
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• v.8 no.2
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• pp.117-135
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• 2019

The lifetime of a gas turbine combustor is typically limited by the durability of its liner, the structure that encloses the high-temperature combustion products. The primary objective of the combustor thermal design process is to ensure that the liner temperatures do not exceed a maximum value set by material limits. Liner temperatures exceeding these limits hasten the onset of cracking which increase the frequency of unscheduled engine removals and cause the maintenance and repair costs of the engine to increase. Hot gas temperature prediction can be considered a preliminary step for combustor liner temperature prediction which can make a suitable view of combustion chamber conditions. In this study, the temperature distribution of ceramic panels for a V94.2 gas turbine combustor subjected to realistic operation conditions is presented using three-dimensional finite difference method. A simplified model of alumina ceramic is used to obtain the temperature distribution. The external thermal loads consist of convection and radiation heat transfers are considered that these loads are applied to flat segmented panel on hot side and forced convection cooling on the other side. First the temperatures of hot and cold sides of ceramic are calculated. Then, the thermal boundary conditions of all other ceramic sides are estimated by the field observations. Finally, the temperature distributions of ceramic panels for a V94.2 gas turbine combustor are computed by MATLAB software. The results show that the gas emissivity for diffusion mode is more than premix therefore the radiation heat flux and temperature will be more. The results of this work are validated by ANSYS and ABAQUS softwares. It is showed that there is a good agreement between all results.

• The KIPS Transactions:PartD
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• v.13D no.2 s.105
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• pp.251-258
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• 2006

Aspect-Oriented Software Development is new software development method. It has many advantages related to software performance, maintenance and repair. Also it offers modularization method to a existing programming language for secondary function such as security and fault tolerance. But the present problem is that we have to use new aspect-oriented programming language. Further more when we apply Aspect to legacy system, we have to recompile the source code in order to build software system based on AOSD. In this paper, we propose and design Connector that can be composed with Aspect in legacy system dynamically. To elaborate this work, we use the information of operations about Core and Aspect, and the information of pointcut described with XML. We validate that the proposed Connector has features such as no need of new compiler, no recompilation and no modification of legacy system through case study.

• 대한공업교육학회지
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• v.33 no.2
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• pp.325-339
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• 2008

In this paper, we developed a module that can execute the data acquisition of the real-time measured radiant rays in the specific part of the nuclear power station. This module that includes the RF communication function, paces around the power station, being loaded on robot and can obtain the generated radiant rays in the various places through the detecting devices. It is considered that this new developed radiant rays acquisition method will have the higher degree of efficiency as compared with the existing method and reduce the expenses of the maintenance and repair work.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.4
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• pp.104-113
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• 2012

This study aimed to find out the improvement plan through analyzing the perception of the expert group engaged in landscape architectural construction and to focus on analyzing the expert groups' experience on Landscape Construction Defects (LCD), defect liability, warranty period, and implementation of the defect liability. The results are as follows: 1. Regarding the experience on the LCD, landscape construction contractors were an awareness of the LCD issue at a serious level, while public-sector clients recognize moderately the LCD issue; and on the first priority in defect implementation, landscape construction contractors considered repair cost while public-sector clients value the identifying causes of defects. 2. In disagreement on the defect liability, landscape construction contractors attributed it to client's lack of responsibility for maintenance while public-sector clients ascribed it to the absence of dealing a criteria with LCD, and regarding the appropriate defect implementation, public-sector clients preferred the following objective by dealing the criteria with LCD while landscape construction contractors advocates by sharing the responsibilities for dealing with LCD based on the identified causes of construction defects. 3. Regarding the warranty period, the public-sector clients considered the 2-year warranty period as appropriate while landscape construction contractors considered it comparatively long, and concerning the commencement of defect warranty period, the public-sector clients viewed it as it should commence to cover the overall completion of the construction while landscape construction contractors perceived it to start on the completion of each work. 4. As for the improvement of the defect implementation system, public-sector clients considered it necessary to establish the objective dealing the criteria with LCD while landscape construction contractors viewed the legislation of maintenance duty. Also, with regard to the important value in establishing and dealing the criteria with LCD, public-sector clients pointed out the objective of the criteria for determining the defects per work type while landscape construction contractors suggested client (user)'s maintenance duty. Because of research, because the system in dealing with LCD is an absence of LCD management agency and dealing the criteria with LCD, it is needed to establish an LCD management agency and make the system in dealing with LCD.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.1
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• pp.81-91
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• 2012

The purpose of this study was to analyze judicial precedents related on landscape construction defects(JPLCD) and suggested the improvement plan for dealing with it. The results are as the following: 1. Landscape construction defects litigations have been increased so far since 2000 and the duration of original trial was approximately 603 days, while appeal trials took up to 550 days. Therefore, the analysis revealed that settlement of disputes were lengthy and wasteful to consumers and constructors. 2. Judgement's cost accepted by the judge was only 53.6% of appraisal's cost appraised by appraiser, therefore it revealed appraiser overestimated the repair cost of landscape construction defects. 3. According to work classification categorized by Landscape Construction Standard Specification(2008) of the Korean Institute of Landscape Architecture, landscape planting amounted to 75% of JPLCD and plaintiff(consumers)'s prevailing rate of it reached 77% to be a serious burden to constructors. 4. According to JPLCD categorized by the type of dispute, defects caused by consumer's negligence for maintenance amounted to 29% and defendant(constructors)'s prevailing rate of it reached 64% to be the main responsibility of consumers. Further study will be required to make the judge standard of landscape construction defects through legal and technical research.