• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.122-129
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• 2020

To conduct probabilistic seismic fragility analysis for nuclear power plants, it is very important to define the failure modes and criteria that can represent actual serious accidents. The seismic design criteria for piping systems, however, cannot fully reflect serious accidents because they are based on plastic collapse and cannot express leakage, which is the actual limit state. Therefore, it is necessary to clearly define the limit state for reliable probabilistic seismic fragility analysis. Therefore, in this study, the limit state of the SCH80 3-inch steel pipe elbow, the vulnerable part of piping systems, was defined as leakage, and the in-plane cyclic loading test was conducted. Moreover, an attempt was made to quantify the failure criteria for the steel pipe elbow using the damage index, which was based on the dissipated energy that used the moment-deformation angle relationship.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.859-866
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• 2022

Active disturbance rejection control is a method in which the disturbance is removed from the controller by estimating the state variable using the Luenberger observer. The Luenberger observer is estimated by defining a nonlinear term including disturbance with constant characteristics in a steady state as a state variable. It can be shown that the speed tracking performance is improved by compensating the estimated state variable to the PI controller and the IP controller. The disturbance removal performance of the tracking control can be confirmed by observing that the estimated state error is within 1.9 [%] in the case of load fluctuation and the steady-state state tracking error converges to zero.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.4
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• pp.80-95
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• 2019

Recently, with the development of sensor and communication technology, researchers at home and abroad have actively conducted research on methodologies for determining maintenance through diagnosis and prediction techniques by collecting information on the status of equipment or systems. Based on the status of vehicle parts at this point in time, this study presented a system framework for making maintenance decisions by predicting the change in vehicle part status to a future date based on the current state of vehicle parts. In addition, condition diagnosis and predictive data adjustment was configured through tracking the status of vehicle parts before and after maintenance activities. We hope that the application of the results of this study will contribute a little to the safety of citizens using public buses and to the activation of the condition-based maintenance system of vehicles.

• Korean Journal of Construction Engineering and Management
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• v.7 no.6
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• pp.185-192
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• 2006

The maintenance expenses of public rental housing have drastically been increased as facilities become obsolete. As an effective means of managing such a situation, accurate estimating of maintenance expenses and securing financial resources are crucially important. It, therefore, is necessary to analyze major factors affecting on maintenance expenses of public rental housing's facilities, and develop an effective instrument to estimate them. On the other hand, the U.S.A, where approximately 60 percent of public rental housing's operating costs are supported by the state, has already developed an effective tool to forecast operating costs based on several years' actual data. As a result, public rental housing has been operating with a reasonable level. However, there have been no remarkable researches and studies in this field in Korea. In this context, this study attempts to examine principal determinants of maintenance expenses of public rental housing's facilities, and their influence based on the latest five years' actual operating costs. This study may contribute to develop an objective and precise tool to forecast maintenance expenses of public rental housing.

• Journal of Wetlands Research
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• v.15 no.3
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• pp.317-328
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• 2013

The aim of this study is to compare the effects of the maintenance water supply methods on the ecological restoration of 5 urban streams such as Mugeo cheon, Yaksa cheon, Yeocheon cheon, Myeongjeong cheon and Cheokgwa cheon in Ulsan metropolitan city. Water quality of the streams have been innovatively improved and the ecosystems have gradually been restored by supplying maintenance water constantly. However, we found that if the maintenance water was in a state of higher salinity or low quality, even enough supply was not helpful and even harmful for ecological restoration. We confirmed that the most important things to create or maintain from the urban stream to the ecological stream are that facilities like a walkway construction should be installed at least, supplying appropriate maintenance water, and a connection with the main stream.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3115-3120
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• 2009

An electric point-machine which changes over a turnout so that it enables a train to be operated in the routine that a train is to proceed has been installed and used in most of the railways such as not only urban railways but also main-line railways. Most of the maintenance works in this electric point-machine is that the maintenance workers manually measure motor power, control power and display power in the site with the use of portable counters. Especially in case of NS or NS-AM electric point machine, the maintenance cycle is so frequent that during the operation casualty accidents caused by carelessness occurs as well as more staff is required for this measurement. In this paper we propose a system for monitoring the state of electric point machine installed in the site to improve maintenance efficiency and it is expected that this monitoring system confirms any measured values on electric point machines in real-time and improves maintenance efficiency.

• Geomechanics and Engineering
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• v.4 no.3
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• pp.219-227
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• 2012

Pavement management systems require systematic monitoring of pavement surfaces to determine preventive and corrective maintenance. The process involves the accumulation of large amounts of visual data, typically obtained from site visitation. The pavement surface condition is then correlated to a pavement distress index that is based on a scoring system previously established by state or federal agencies. The scoring system determines if the pavement section requires maintenance, overlay or reconstruction. One of the surface distresses forming part of the overall pavement distress index is the Alligator Crack Index (AC Index). The AC Index involves the visual evaluation of the crack severity of a section of a pavement as being low, medium, or high. This evaluation is then integrated into a formula in order to obtain the AC Index. In this study a quantification of the visual evaluation of the severity of alligator cracking is carried out using photographs and the fractal dimension concept from fractal theory. Pavements with low levels of cracking were found to have a fractal dimension equal to 1.051. Pavements with moderate levels of cracking had a fractal dimension equal to 1.1754. Pavements with high degrees of cracking had a fractal dimension that varied between 1.5037 (high) and 1.7111 (very high). Pavements with a level of cracking equal to 1.8976 represented pavements that disintegrated and developed potholes. Thus, the visual evaluation of the state of cracking of a pavement (the AC Index) could be enhanced with the use of the fractal dimension concept from fractal theory.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2527-2538
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• 2011

The Reliability started for MILitary purposes during World War II in 1942, getting more important for maintenance, safety, etc in modern society. As technologies develop, also international standards for measuring the reliability is advancing. RAMS activities for maintenance, safety verification is material to national railroad. And for this, it needs quick response for the changes of standards. Even now standards are upgrading for developing electronic technologies. Therefore analysis of failure rate's trend about such standards is judged necessary. So We submit a this paper for comparative analysis of changing process standards according to development of electronic technologies and reliability. At first, we compared actual usage ratio of standards for understanding the current state of usage. Based of these state of usage, discuss the major standard. And then, introduced reliability standards's trend, calculation method of failure rate and difference of failure rate calculation standard according to march of time. In this paper, used standards are MIL-HDBK-217F, Telcodia, etc.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.150-159
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• 2014

A simplified method for the calculation of buckling and vibrational characteristics of initially stressed rectangular plate and antisymmetric angle-ply laminated plates is presented in this paper using the natural frequencies under unloading state. The equation of motion of rectangular plate with two opposite edges simply supported is investigated on the basis of Rayleigh-Ritz method and Mindlin plate theory with effect of the curvature term. The relationships of the non-dimensional natural frequencies with initial stresses the coeffcients of critical buckling and the boundaries of the dynamic principal instability region can be characterized by the non-dimensional natureal frequencies under unloading state. Numerical examples are presented to verify the simplified equations and to illustrate potential applications of the analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.4
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• pp.149-160
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• 2000

As systematic methodologies are required for the evaluation on the durability of reinforced concrete structure, it is necessary to study and examine every factor which deteriorates the durability of structures. This paper aims to define factors affecting rebar corrosion and to establish a basis for a prediction of serviceability, regarding a state of harmful corrosion as a state when crack begins on the surface of concrete. The study results are followings; The corrosive current has changed by types of mixture, and this property enables the evaluations of corrosion resistance by mixture and concrete cover. The specimen using AE superplasticizer has better corrosion-resistance properties than non-AE specimen, as well those having low W/C and high unit cement weight. The procedure for calculation of durable year in this study is able to use as an indicator to establish mixture factors such as unit cement weight, W/C, amount of admixture, etc.