• Computational Structural Engineering : An International Journal
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• v.1 no.1
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• pp.71-80
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• 2001

A reliability approach to evaluate structural performance has gained increased acceptability and usage over the past two decades. Most reliability analyses are based on the reliability of an individual component without examining the entire structural system. These analyses often result in either unnecessary repairs or unsafe structures. This study uses examples of series, parallel, and series-parallel models of structural systems to illustrate how the component reliabilities affect the reliability of the entire system. The component-system reliability interaction can be used to develop optimum lifetime inspection and repair strategies for structural systems. These examples demonstrate that such strategies must be based on the reliability of the entire structural system. They also demonstrate that the location of an individual component in the system has a profound effect on the acceptable reliability of that component. Furthermore, when a structure is deteriorating over time, the reliability importance of various components is a1so changing with time. For this reason, the most critical component in the early life of the structure may not tie the most critical later.

• Journal of the military operations research society of Korea
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• v.24 no.1
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• pp.98-109
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• 1998

This study develops a maintenance strategy for a reparable 2-unit standby system. The maintenance strategy implies the waiting time to call the repair facility when the unit-1 fails. Almeida and Souza set up the multi-attribute utility function consisting of system availability and repair cost for several maintenance strategies and decide the optimal maintenance strategy that maximize the expected value of the utility function. We decide the optimal maintenance strategy satisfying the following two criteria about the utility function : maximum variance using Almeida and Souza's utility function. It both criteria are not satisfied at the same time for every strategies, the strategy maximizing the lower confidence limit for expected utility function is regarded as an optimal one.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.146-147
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• 2017

Recently, as the living standards of residents in apartment houses continued to improve, the dispute of post management have also increased. one of the Issue, Concrete Cracks comprised high percentage of dispute. Especially, between criteria the cost of repairing defect and the judgement of defect isn't clear, they are a lot of dispute in this regard. Even though lots of the criteria about Inter-layer crack is existed by judging defects, In a court, they are judging their own criteria about Inter-layer crack. The purpose of this study is to compare and analyze Defect Judement Standard both MOLIT and Court, and to provide the Improvement for Defect Judgement and Repair Method of Inter-layer concrete crack.

• Journal of Information Technology Services
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• v.13 no.3
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• pp.275-298
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• 2014

The purpose of this study is to verify the difference between the importance level and the satisfaction level of each purchase decision factor of smart phone. Through review of literatures about purchase decision factors, we have derived about attributes of 6 factors. T-test, importance performance analysis (IPA), and regression analysis were conducted to identify priorities among the details of the importance and satisfaction and to analyze the effect relationship between satisfaction of each factor and overall satisfaction. Looking at a few high-priority order, battery capacity, memory capacity, fast and accurate repair, the adequacy of the repair cost, and processor in the top five factors were shown to be an important factor when purchasing smart phones. The results of this study can provide the marketing strategies for smart phone suppliers. In addition, these results imply what factors of smart phones should be more considered before launching into chinese smart phone market.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.115-118
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• 2000

The development of high-strength fibers such as boron/epoxy and carbon/epoxy and adhesives has made it possible to repair cracked metallic plates by bonding reinforcing patches to the plate over the crack. In this study, aluminum 6061-T6 alloy plates with the high strength are applied to specimens with a cracked bolt hole to study the effect of diverse patch materials on the fatigue behavior of this structure. Additionally, the observation of the effort of different patch sizes on the specimen was performed. The results shows that the patch repair can improve the static strength by about 17% and the fatigue life by 200% compared with non-repaired case. And it was also revealed that the patching method along to crack growth direction is mort efficient in cost and weight reduction.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.228-233
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• 2004

The length of city gas pipeline is increasing with expansion of natural gas transmission rapidly. A lot of the expense was paid for repair and maintenance with increasing of pipeline length and the cost of repair and maintenance by the corrosion was the highest. It is necessary to evaluate integrity in case of thickness reduction by corrosion. There are a lot of assessment criteria for corrosion defect in foreign countries but they are not suitable for application in the country directly. In this work, we performed the burst test and the finite element analysis for city gas pipeline, KS D3507 and KS D3631 for city gas transmission, and developed the assessment method of corrosion defect, which is suitable for domestic condition.

• Journal of Korea Ship Safrty Technology Authority
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• s.24
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• pp.4-20
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• 2008

Stainless steel 304 or stainless steel 630 types using propeller shaft of a small ship or a FRP fishing boat generally restrain localization corrosion and abrasion damage occurrence to shaft bearing or grand packing contact. In general, the residual stress which remains after welding or heat treatment in material can cause the stress concentration or localization corrosion. In case of small ship, stainless steel such as STS304 has long been used for propeller shaft. Meanwhile, crew of small ship tend to reuse damaged propeller shaft after repair by welding and performing heat treatment to save cost. However, it was found that reused propeller shaft by repair often caused troubles in ship's operation. In this study, the basic guideline for maintenance and treatment of propeller shaft are investigated. From the results of investigation, remarkable deterioration of the material properties and corrosion resistance on the welded work part was observed.

• Proceedings of the Safety Management and Science Conference
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• 2004.11a
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• pp.115-123
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• 2004

Replacement problems can be classed as either deterministic of stochastic. Deterministic problems are those in which the timing and the outcome of the replacement action are assumed to be known with certainty. Before proceeding with development of replacement models it is important to note that preventive replacement actions, that is, ones taken before equipment reaches a failed state, require two necessary conditions: (1) The total cost of the replacement must be greater after failure than before. (2) The failure rate of the equipment must be increasing. Equipment is subject to failure. On failure, one of two possible actions can be taken : repair or complete replacement of the failed equipment. In this paper, we proposed optimal overhaul, repair, replacement maintenance model with two-state.

• Computers and Concrete
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• v.11 no.4
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• pp.351-364
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• 2013

This paper presents results from an analytical investigation of the behavior of steel reinforced concrete circular column sections with additional Glass Fiber Reinforced Polymers (GFRP) bars. The primary application of this composite section is to relocate the plastic hinge region from the column-footing joint where repair is difficult and expensive. Mainly, the study focuses on the development of the full nominal moment-axial load (M-P) interaction diagrams for hybrid concrete sections, reinforced with steel bars as primary reinforcement, and GFRP as auxiliary control bars. A large parametric study of circular steel reinforced concrete members were undertaken using a purpose-built MATLAB(c) code. The parameters considered were amount, location, dimensions and mechanical properties of steel, GFRP and concrete. The results indicate that the plastic hinge was indeed shifted to a less critical and congested region, thus facilitating cost-effective repair. Moreover, the reinforced concrete steel-GFRP section exhibited high strength and good ductility.

• Industrial Engineering and Management Systems
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• v.2 no.1
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• pp.63-70
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• 2003

In this study, we employed an arithmetic process (AP) approach to resolve gearbox maintenance problems. The approach is realistic and direct in modelling the characteristics of a deteriorating system such as a gearbox since a decreasing AP can model a gearbox's successive operating times and an increasing AP can model the corresponding consecutive repair times. First of all, two test statistics were used to check whether the process is arithmetic or not. Next, model parameters of the AP were estimated using the simple linear regression method. Finally, the optimal replacement policy based on minimising the long-run average cost per day was determined for each type of gearbox.