• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.3
• /
• pp.171-177
• /
• 2010

As concrete structures are exposed to chemical substances, damaged from salt, or progressed to the neutralization, the surface damage of the structures is generated timely fashion, resulting shortened service life. Especially, the sulfate erosion causes rapid surface defects, and the steel skeleton becomes corroded due to the water infiltration, generating stability deterioration of the concrete structure. In this study, the physical characteristics of the acid-resistant mortar with aluminosilicates was investigated in order to resolve problems of the acid resistance, one of the most serious problems of the cement type repair material. As the result of the experiment, the test specimen turned to exhibit almost equivalent physical characteristics with those of concrete sectional repair materials in terms of compressive and bending strengths. As both the cement sectional repair material and the test specimen were immerged in sulfuric acid solution to examine weight changes, the test specimens exhibited only 4% loss of their weights while the cement sectional repair materials reached at the level of 80% or above, proving the excellence acid resistant characteristics of the test specimens. Consequently, the physical characteristics of acid resistant mortar with aluminosilicates were revealed to be superior than those of concrete sectional repair materials. It can be utilized as a sectional repair material where the acidic erosion is anticipated.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.5
• /
• pp.97-104
• /
• 2023

The aim of this study was to produce polymer cement composites (PCCs) composed of polymer dispersion and cement as crack repair materials for RC structures, and to investigate their fundamental properties. The test mixtures for the study were based on EVA and SAE polymer dispersions, and the water-cement ratio was determined while varying the polymer-cement ratio(P/C) in four different levels (20%, 60%, 80%, and 100%) to achieve the desired viscosity of PCCs considering their fillability as crack repair materials. Additionally, silica fume was incorporated into P/C 80% and 100% specimens to enhance their stiffness. The basic properties of PCCs as crack repair materials, such as viscosity, flowability, fillability, tensile strength, elongation, and modulus of elasticity, were examined. The results showed that P/C depending on the type of polymer significantly affected the viscosity and flowability, and appropriate w/c ratios were needed to achieve the desired viscosity for the mixture design with consideration of fillability as crack repair materials for RC structures. All designed mixtures in this study exhibited excellent fillability. The tensile strength and elongation of PCCs satisfied the KS regulation for cement- polymer modified waterproofing coatings. The incorporation of silica fume improved the tensile strength and modulus of elasticity of PCCs. Depending on the type of polymer, mixtures using SAE showed better fundamental properties as crack repair materials for RC structures compared to those using EVA. In conclusion, SAE-based P/C 80% or 100% with the addition of up to 30% silica fume can be recommended as suitable mixtures for crack repair of RC structures.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.03a
• /
• pp.284-293
• /
• 2002

Using the life cycle cost concept, optimum maintenance and retrofit planning for reliable seismic performance is suggested the overall life cycle cost to be minimized including the initial cost, the costs of inspection, repair, and failure. Limit states of the bridges are defined. And failure probabilities are computed through crossing theory. The effect of maintenance and retrofit is represented using the probability of damage detection and event tree analysis. Optimization of maintenance and retrofit planning method proposed from this research was applied to numerical examples. The analysis incorporates the acceleration and site conditions prescribed in the code, and the quality of inspection methods.

• Korean System Dynamics Review
• /
• v.12 no.1
• /
• pp.115-130
• /
• 2011

This study shows the operational availability(Ao) analysis of the supply chain with maintenance functions using the system dynamics simulation. The simulation uses 60 equipments which are serial systems composed by 4 major components. And every entities are connected each other by causal loops. So whole simulation executed like one organic system. Specially we consider 2 constraints, one is the number of spare parts and the other is maintenance capacity level. 2 constraints have 11 levels each so the simulation has 121(11*11) scenarios which scenario has 30 different random number seed. The simulation executed total 3,630(11*11*30) times. We analysis average Ao of total equipments by 121 scenarios and additionally the regression of the average Ao and 2 constraints. As the result, we can get the more accurate values by the system dynamics simulation than the regression to analysis complex system like the supply chain with maintenance functions.

• Proceedings of the Korean Statistical Society Conference
• /
• 2005.11a
• /
• pp.73-78
• /
• 2005

This paper considers a preventive maintenance policy following the expiration of renewing warranty, Most preventive maintenance models assume that each PM costs a fixed predetermined amount regardless of the effectiveness of each PM. However, it seems more reasonable to assume that the PM cost depends on the degree of effectiveness of the PM activity. In this paper we consider a periodic preventive maintenance policy following the expiration of renewing warranty when the PM cost is an increasing function of the PM effect. The optimal number and period for the periodic PM policy with effect dependent cost that minimize the expected cost rate per unit time over an infinite time span are obtained.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.32 no.2
• /
• pp.171-178
• /
• 2009

Logistic support activities for weapon systems play an important role at maintenance activities in modern warfares. These activities are essential for keeping weapon systems ready at all time. However, maintenance supplies can be delayed without a proper information system. Further, increases of mean time to repair (MTTR) and unavailability of weapon systems can be occurred. In this study, a web based information system is developed for logistic chains of class 9 supplies. Utilizing web database technologies, the developed system can provide an environment for data exchange and sharing among various participants in the supply chain.

• Proceedings of the SAREK Conference
• /
• 2008.11a
• /
• pp.481-486
• /
• 2008

The building HVAC systems have very different qualities of performance and durability with the superintendent's ability for management and maintenance. The poor management of these systems finally lead to the shortening of the life expectancy and result in the increase of operating costs and energy consumptions due to low efficiencies. So it is essential to try to develop ways to adequately maintain and to use the building facilities efficiently in order to preserve earth environment and the limited resource. In this study, the LCC based numerical calculation package will be developed for the efficient maintenance plan and the determination of the reasonable time of repair or replacement of equipments.

• Proceedings of the KSR Conference
• /
• 2005.11a
• /
• pp.382-388
• /
• 2005

SMSC(Seoul Metropolitan Subway Corporation) is substantially taking the core role of mass transit system in Seoul Metropolitan area. When it was built, the design had challenged to sharp curved tracks less than 250m radius considering the protection of buildings and cultural properties as well as the connection to ground roads. Such circumstances have required a certain extent of slack in track geometry and therefore led to the construction of ballasted track with wooden sleepers. However, the dynamic force from running on sharp curved track has caused the misalignment and abnormal failure of track geometry, and it has resulted in a frequent maintenance and repair works which require a lot of cost and manpower. In this paper, we present the construction case of maintenance-free track system by using of concrete sleeper and elastic rail fastening system to ensure the safety of both passengers and trains, and to contribute the effective maintenance for track facilities of SMSC.

• International Journal of Railway
• /
• v.1 no.4
• /
• pp.134-142
• /
• 2008

Serving as a strategic crossing point for major corridors in Central Europe, Railnet Austria's Infrastructure Network incurs continual increases in international traffic flows and is therefore subject to accumulating traffic congestion with potential restrictions to infrastructure access. This imposes challenges towards preserving open access to Railnet Austria's existing railway network and hinders quality infrastructure service during maintenance, repair, and upgrading. Through Railnet Austria's experiences, the economic viability of a railway network can be sustained through maintaining open access with good quality service of planned trainpaths, thus representing new challenges for future infrastructure maintenance and capacity planning. Railnet Austria's Capacity Management Department has proven that these challenges can be accommodated more effectively through recent technological developments in data warehousing and software development.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2011.05a
• /
• pp.177-178
• /
• 2011

Recently a great deal of people are taking legal action against the housing provider due to the defects of their Apartment house. And most of the housing companies are spending a huge amount of expenses and efforts to keep their brand value. This essay will carry out time series analysis the 20 housing district which are constructed by huge construction companies. This analysis itemised by metropolitan area(Seoul) and others to keep the degree of reliability, and converted future defect maintenance cost into current cost applied by discount rate to figure out suitability of defect maintenance cost. Even though, this essay is not able to represent standard of defect maintenance cost due to the insufficiency of record, while it will be assisted as a referance when long-term record of time series is estabilished.