• The Journal of Sustainable Design and Educational Environment Research
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• v.10 no.1
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• pp.10-25
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• 2011

Area Offices of Education in Korea assign and execute government budget based on the evaluation of school buildings' safety rating and degree of their deterioration. However, it is never easy to estimate the most appropriate investment amount for old buildings under consideration of their service lives and residual values together. A model of estimating optimum investment cost for obsolete school building is developed taking its life cycle cost into account. The model is also applied to six old buildings in five different schools and found that some of the facilities hardly needed further investment and were better to be rebuilt. The study results will be a great beneficial for officers to make right decision on maintaining obsolete school buildings and to maximize tax payers' money.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.633-636
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• 1998

This study is performed for the purpose of obtaining the fundamental datum to analyse the cause of steel corrosion in concrete and establish the repair strategies of deteriorated reinforced concrete structures due to steel corrosion. To investigate the degree of concrete deterioration, soluble chloride content in harden concrete, the depth of carbonation, cover depth and compressive strength are measured. The progress of corrosion of concrete bridge is electrochemically evaluated. The result shows that in approximately 43% of the structures below -350mV(vs. CSE), the exessive chloride contents is a direct cause of steel corrosion in reinforced concrete structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.731-736
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• 2002

The degradation of reinforced concrete (RC) structures due to physical and chemical attacks has been a major issue in construction engineering. Deterioration of RC structures due to chloride attack followed by reinforcement corrosion is one of the serious problems. The objective of this study is to develop a form of mathematical model of chloride ingress into concrete. In order to overcome some limits of the previous approaches, a mathematical model of chloride ingress into concrete consisting of chloride solution intrusion through the capillary pore and chloride ion diffusion through the pore water was proposed. Moreover, the variability of diffusivity of chloride ion due to degree of hydration of concrete, relative humidity in pore, exposure condition, and variation of chloride binding was considered in the chloride ingress model.

• Journal of Chest Surgery
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• v.12 no.4
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• pp.365-370
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• 1979

The first Mitral Commissurotomy was performed for tight mitral stenosis on March 1957. The patient was at that time 22-year-old male, student. The longest follow 9p for 22 years and 8 months has been obtained. During the follow up period, late deterioration due to restenosis developed 4 years after initial good result and reoperation was succeeded by transventricular Mitral Valvotomy with Tubb`s ilator on April 1964. The possible cause of restenosis was attributed to recurrent rheumatic activity. After more than 13 years long-good life following 2nd operation, Endocarditis such as episode of high fever & chill intermittently followed by mild fever and night sweat, I t. tibial artery embolization and rupture of aortic cusp. At present, patient complained of no subjective symptom, enjoying ordinary life {NYHA II]. Blood pressure has been 110/50-60 mmHg, trivial diastolic murmur at apex and moderate degree of mechanical murmur on diastole at Erb`s rea. Neither signs of RVH for mitral stenosis nor sign of LVH. ST-T change for aortic regurgitation appeared yet during last 2 yrs. The patient`s are for prevention of Rheumatic activity and development of endocarditis is important for obtaining the better long-term result.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.437-442
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• 1999

Corrosion of steel reinforcment is the most significant factor of deterioration in reinforced concrete structures. Chloride ion is considered one of the most common culprits on the corrosion of steels in concrete. This study is effect of cement hydraulic degree on the chloride binding in hardened cement pastes. With increasing the cement hydration, cement products such as CSH and Ca(OH)2 were increased, and the part of added chloride were binded with them. With respect to A type, in first, the additional contents of chloride of 27.08mM/L in pore solution were reduced as 4.3mM/L at 3 days, 4.0mM/L at 7 days, 3.6mM/L at 28 days.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.83-88
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• 1996

Reinforced-concrete structures built on the seashore or in seawater are damaged from flying-salt of chloride ion in the seawater. Recently many bridges are being constructed under marine enviornment and there are many serious problems of chlofide attack owing to penetration of chloride ion. And up to now it has not only so little a seatch about damage from flying-salt and seawater but also little systematic study outcome about steel corrosion. In this study we investigate the concrete deterioration and steel corrosion of RC bridges on the seashore. Environmental conditions are investigated, and compressive strength, carbonation depth and steel-corrosion degree are measured.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1851-1853
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• 1996

In this paper the criteria for insulating oil condition of pole transformer were suggested by applying the UV-Visible spectrophotometric method. Ageing of insulating oil caused the change in absorbances of oil os well os the deterioration of electrical properties of oil. By comparing the electrical properties such as $tan{\delta}$ and breakdown voltage with the UV-Visible absorbances of oil, criteria for absorbance values determining oil condition were established. This UV-Visible spectrophotometric method might be applied in ageing analysis of oil and be expected to replace the current method.

• Steel and Composite Structures
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• v.23 no.2
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• pp.239-250
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• 2017

In the concept of two-parameter fatigue failure criterion, the material fatigue failure is determined by the damage degree and the current stress level. Based on this viewpoint, a residual strength degradation model for stud shear connectors under fatigue loads is proposed in this study. First, existing residual strength degradation models and test data are summarized. Next, three series of 11 push-out specimen tests according to the standard push-out test method in Eurocode-4 are performed: the static strength test, the fatigue endurance test and the residual strength test. By introducing the "two-parameter fatigue failure criterion," a residual strength calculation model after cyclic loading is derived, considering the nonlinear fatigue damage and the current stress condition. The parameters are achieved by fitting the data from this study and some literature data. Finally, through verification using several literature reports, the results show that the model can better describe the strength degradation law of stud connectors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.3
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• pp.287-291
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• 2006

This paper describes mechanical and electric properties of ACSR $410\;mm^2$ conductor from many of older overhead conductor. Samples of conductors itemized two division according to operation sector, green area, salt and pollution area. Samples of conductors operated various environment conditions have undergone laboratory metallurigical investigation and tensile strength torsional ductility and electrical performance. The steel core were found to have retained their original properties to a large degree in both tensile strength and the number of turns to failure. On the other hand the aluminum conductor showed reductions in tensile strength. To determine the remaining useful life of aged conductor, an unacceptable deterioration level has to established for each diagnostic procedure.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.1
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• pp.25-29
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• 2012

In this paper, in order to measure the degree of degradation using the reflection coefficient of the probe, the measuring circuit is designed. we put pulse signal into the probe and measure the reflected signal in the circuit. As the condition of engine oil degradation, we can see that the reflected signal was increased and as the engine oil temperature increases, a phenomenon shows that the degradated dielectric constant is decreased. Finally, the theoretical values and measured values of the reflection coefficients of the probe are analyzed.