• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.56-61
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• 2013

This paper presents the results of integrity assessment for the cracks happened in reactor vessel upper head penetration nozzles. The crack morphology for a boat sample from crack area was analyzed through microscope. The stress condition including weld residual stress around crack was analyzed using finite element analysis. From the results of crack morphology and stress condition, the crack was concluded as primary water stress corrosion cracking. The integrity of the cracked nozzle was assessed by the methodology provided in ASME Section XI. According to the assessment results, the remaining life of the cracked nozzle was 1.43 yrs. and the plant decided to repair it.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1196-1202
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• 2007

In construction of high speed railway, the fan shape is limited to achieve reduction of required travel time and concrete railway which has structural stability and induces small maintenance cost with allowable ground settlement is recently applied. So construction of concrete railway on soft ground in which considerable ground settlement occurs increases and settlement management in soft ground section is required. Field monitoring on ground movement and integrated geotechnical information system which manages construction, design, and field monitoring data are essential for settlement management of concrete railway subgrade. Site investigation data are also required due to future repair work. Therefore in this study, integrated geotechnical information system for construction and maintenance of concrete railway is developed. The developed system consists of a database and an application program. The database contains site investigation, construction, design, and field monitoring data throughout a railway. Application program performs various functions on managing and utilizing information in the database with graphic visualization of output. And by providing integrating information with comprehensible visual displays, the applicability and effectiveness of the developed system for construction and maintenance management were confirmed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.622-627
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• 2012

During helicopter rotor system development process, whirl tower test is conducted basically. For conducting whirl tower test during bearingless hub development process, design new blade or using existing blade with repair or remodeling. Because simple shape and efficient aerodynamic characteristic, BO-105 blade is used for hub system development widely. Originally BO-105 blade is used for hingeless hub, ho flap stiffness and lag stiffness on blade root area is relatively low. So applying BO-105 blade to bearingless hub whirl tower test, root area have to be reinforce. In this process, blade root area's section property will be changed. In this paper, suggest reinforcement method of BO-105 blade root area and study dynamic characteristic of bearingless rotor system with reinforcement BO-105 blade.

• Corrosion Science and Technology
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• v.3 no.4
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• pp.166-171
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• 2004

Recent developments in Bridge Management Systems (BMS) and in Life-Cycle Cost (LCC) of bridges, have raised the need for evaluation procedure of future condition (Deterioration) of a bridge. Predicting future deterioration is not an easy task due to limited past data to extrapolate from and also due to difficulty in measuring actual deterioration such as section loss of steel on an actual steel bridge. Also, increase in live load and reduction of resistance are random variables, thus a probabilistic approach should be adopted for determining the future deterioration. Due to difficulties in evaluation of future deterioration on steel bridges, accepting uncertainties within a reasonable error, a deterministic procedure using bridge condition rating can be a useful tool for projection of future condition of bridges to identify repair and maintenance needs. The object of this paper is to determine applicability of evaluating deterioration of steel bridge components based on Bridge condition ratings. Bridge condition ratings of bridge components show wide variation for bridges of same age and does not directly correlate well with the age of the bridge and/or deterioration of the bridge. High uncertainty can be reduced by breaking down the rating and by sensitivity analysis. From refined condition rating data, generalized deterioration profile of structures based on age can be derived. Examples are shown for sample bridges in USA. Approximately, 3,000 short to medium span steel bridges were listed in the inventory database. Results show wide variation of rating factors but by subdividing the Bridge condition ratings for various categories general deterioration profiles of steel bridges can be determined.

• Computers and Concrete
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• v.16 no.3
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• pp.399-414
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• 2015

Nowadays, fiber reinforced polymer (FRP) composites are widely used for rehabilitation, repair and strengthening of reinforced concrete (RC) structures. Also, recent advances in concrete technology have led to the production of high strength concrete, HSC. Such concrete due to its very high compression strength is less ductile; so in seismic areas, ductility is an important factor in design of HSC members (especially FRP strengthened members) under flexure. In this study, the Adaptive Neuro-Fuzzy Inference System (ANFIS) and multiple regression analysis are used to predict the curvature ductility factor of FRP strengthened reinforced HSC (RHSC) beams. Also, the effects of concrete strength, steel reinforcement ratio and externally reinforcement (FRP) stiffness on the complete moment-curvature behavior and the curvature ductility factor of the FRP strengthened RHSC beams are evaluated using the analytical approach. Results indicate that the predictions of ANFIS and multiple regression models for the curvature ductility factor are accurate to within -0.22% and 1.87% error for practical applications respectively. Finally, the effects of height to wide ratio (h/b) of the cross section on the proposed models are investigated.

• Corrosion Science and Technology
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• v.16 no.2
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• pp.85-89
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• 2017

One of the most challenging issues in the oil and gas industry is corrosion assessment and management in subsea structures or equipment. At present, almost all steel pipelines are sensitive to corrosion in harsh working environments, particularly in salty water and sulphur ingress media. Nowadays, the most commonly practiced solution for a damaged steel pipe is to entirely remove the pipe, to remove only a localized damaged section and then replace it with a new one, or to cover it with a steel patch through welding, respectively. Numerous literatures have shown that fiber-reinforced polymer-based composites can be effectively used for steel pipe repairs. Considerable research has also been carried out on the repair of corroded and gouged pipes incorporated with hybrid natural fiber-reinforced composite wraps. Currently, further research in the field should focus on enhanced use of the lesser and highly explored hybrid-biocomposite material for the development in corrosion prevention. A hybrid-biocomposite material from renewable resource based derivatives is cost-effective, abundantly available, biodegradable, and an environmentally benign alternative for corrosion prevention. The aim of this article is to provide a comprehensive review and to bridge the gap by developing a new hybrid-biocomposite with superhydrophobic surfaces.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.105-111
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• 2015

Since 2007, Insurance Institute of Highway Safety(IIHS) has conducted the new bumper test using bumper barrier to estimate the repair cost of impacted vehicle. In this study, for the front body FE model of a medium size passenger car analyzes were carried out to optimize the shape of backbeam center reinforcement bracket. First, overlap effect was examined with changing the overlap magnitude and spot welds were added along the backbeam center line for reducing the section shear deformation. Next, for an overlap model design parameter study was performed for the bracket. Thickness effect was examined and an inner reinforcement was added to the bracket. Also, the lower part of bracket was deleted and additionally the bracket length was extended. The results were discussed in terms of backbeam backward deflection, barrier backstop intrusion and weight. Compared with the current design, the final model showed 44.1% bracket weight reduction with 30.0% decrease of backbeam deflection.

• Structural Monitoring and Maintenance
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• v.10 no.3
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• pp.221-242
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• 2023

Internal and external corrosion are common in pressure pipes used in a variety of industries, often resulting in defects that compromise their integrity. This economically and industrially significant problem calls for both preventive and curative technical solutions to guarantee the reliability of these structures. With this in mind, our study focuses on the influence of composite and metallic patch repairs on the limit loads of pipes, particularly elbows, the critical component of piping systems. To this end, we used the nonlinear extended finite element method (X-FEM) to study elbows, a priori corroded on the internal surface of the extrados section, then repaired with composite and metallic patches. In addition, the effect of the geometry of composite materials and metal patches was examined, in particular the effect of their thickness and material on the increase in limit loads of repaired structures. The results obtained provide information on the effectiveness and optimization of patch repair of corroded elbows, with the aim of increasing their service life.

• Journal of Korea Water Resources Association
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• v.56 no.2
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• pp.103-113
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• 2023

The river confluence is a section in which two rivers with different topographical and hyrodynamic characteristics are combined into one, and it is a section in which rapid flow, inflow of sediments, and hydrological topographic changes occur. In the confluence section, the flow of fluid occurs due to the difference in density due to the type of material or temperature difference, which is called a density flow. It is necessary to accurately measure and observe the confluence section including a certain section of the main stream and tributaries in order to understand the mixing behavior of the water body caused by the density difference. A comprehensive analysis of this water mixture can be obtained by obtaining flow field and flow rate information, but there is a limit to understanding the mixing of water bodies with different physical properties and water quality characteristics of rivers flowing with stratigraphic flow. Therefore, this study attempts to grasp the density flow through the water temperature distribution in the confluence section. Among the extensive data of the river, vertical data and water surface data were acquired, and through this, the stratification phenomenon of the confluence was to be confirmed. It was intended to analyze the mixed pattern of the confluence by analyzing the water mixing pattern according to the water temperature difference using the vertical data obtained by measuring the repair volume by installing the ADCP on the side of the boat and measuring the real-time concentration using YSI. This study can supplement the analysis results of the existing water quality measurement in two dimensions. Based on the comparative analysis, it will be used to investigate the current status of stratified sections in the water layer and identify the mixing characteristics of the downstream section of the river.

• Clinics in Shoulder and Elbow
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• v.15 no.1
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• pp.16-24
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• 2012

Purpose: This study was designed to investigate the rate of incidence, location and the clinical value of the rotator cuff retear by analyzing MRI scans, which was taken after an arthroscopic rotator cuff repair. Materials and Methods: This study included a total of 109 patients, who underwent a shoulder MRI scan after an average of 10.6 months later from the arthroscopic rotator cuff repair. We only defined the 'retear' when the Sugaya type IV and V was observed in the sagittal section of the MRI. The location of the retear was divided into the medial and lateral areas by the site, which was 1 cm medial to the anchor insertion. We investigated the incidence rate and the location of the retear, in terms of the age, sex, initial tear size and the suture method. Also, we compared the functional score of the retear group and the non-retear group, after an average of 13.9 months follow-up. Results: There were 38 of the 109 patients that showed the rotator cuff retear. Of these patients, 25 were male patients, and 13 were female patients. Of the 38 patients with the rotator cuff retear, 21 patients were included in the <3 cm retear group, and 17 were included in the ${\geqq}3$ cm retear group. At the end of the follow up period, all 109 patients showed a statistical significant improvement in the shoulder functional score. Conclusion: According to the follow up of the MRI scan, which was taken after the rotator cuff repair, the retear rate reached 34.9 %, and there were no significant differences on the age and the suture method. More rotator cuff retear occurred in male patients, and the initial tear size was positively correlated with the incidence rate of the rotator cuff retear. Also, the retear was more frequently observed at the medial side. That is because when the suture was performed, excessive tension was loaded on the medial side of the suture site.