• Proceedings of the SAREK Conference
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• 2007.06a
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• pp.48-48
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• 2007

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.213-220
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• 2004

This paper deals with an enhanced structural capacity of reinforced concrete bridge deck strengthened with carbon fiber rod (CFR) which is subjected to monotonic and cyclic loads. Strengthening variables considered in this test were evenly and unevenly strengthening type. To evaluate strengthening capacity for these two strengthening types, load-carrying capacity and crack and failure pattern from the failure test were analyzed and fatigue response were examined. According to the test results, all the strengthened specimens showed punching shear failure as a result of premature failure of bonding interface between mortar and concrete. In the case of strengthening capacity, it was observed that the strengthened specimens was more effective in strength, stiffness and fatigue endurance limit than the unstrengthened specimen. In addition, the unevenly strengthening method (CR-UE) was more effective than the evenly strengthening method (CR-E).

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.69-75
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• 2014

Purpose: The aim of this study was to evaluate changes of quantitative and semi-quantitative myocardial perfusion indices and image quality by image reconstruction methods in $^{13}N$-ammonia ($^{13}N-NH_3$) myocardial perfusion PET/CT. Materials and Methods: Data of 14 (8 men, 6 women) patients underwent rest and adenosine stress $^{13}N-NH_3$ PET/CT (Biograph TruePoint 40 with TrueV, Siemens) were collected. Listmode scans were acquired for 10 minutes by injecting 370MBq of $^{13}N-NH_3$. Dynamic and static reconstruction was performed by use of FBP, iterative2D (2D), iterative3D (3D) and iterative TrueX (TrueX) algorithm. Coronary flow reserve (CFR) of dynamic reconstruction data, extent(%) and total perfusion deficit (TPD) (%) measured in sum of 4-10 minutes scan were evaluated by comparing with 2D method which was recommended by vendor. The image quality of each reconstructed data was compared and evaluated by five nuclear medicine physicians through a blind test. Results: CFR were lower in TrueX 18.68% (P=0.0002), FBP 4.35% (P=0.1243) and higher in 3D 7.91% (P<0.0001). As semi-quantitative values, extent and TPD of stress were higher in 3D 3.07%p (P=0.001), 2.36%p (P=0.0002), FBP 1.93%p (P=0.4275), 1.57%p (P=0.4595), TrueX 5.43%p (P=0.0003), 3.93%p (P<0.0001). Extent and TPD of rest were lower in FBP 0.86%p (P=0.1953), 0.57%p (P=0.2053) and higher in 3D 3.21%p (P=0.0006), 2.57%p (P=0.0001) and TrueX 5.36%p (P<0.0001), 4.36%p (P<0.0001). Based on the results of the blind test for image resolution and noise from the snapshot, 3D obtained the highest score, followed by 2D, TrueX and FBP. Conclusion: We found that quantitative and semi-quantitative myocardial perfusion values could be under- or over-estimated according to the reconstruction algorithm in $^{13}N-NH_3$ PET/CT. Therefore, proper dynamic and static reconstruction method should be established to provide accurate myocardial perfusion value.

• Earthquakes and Structures
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• v.16 no.2
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• pp.221-234
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• 2019

Today, many important concrete face rockfill dams (CFRDs) have been built on the world, and some of these important structures are located on the strong seismic regions. In this reason, examination and monitoring of these water construction's seismic behaviour is very important for the safety and future of these dams. In this study, the nonlinear seismic behaviour of Ilısu CFR dam which was built in Turkey in 2017, is investigated for various reservoir water heights taking into account 1995 Kobe near-fault and far-fault ground motions. Three dimensional (3D) finite difference model of the dam is created using the FLAC3D software that is based on the finite difference method. The most suitable mesh range for the 3D model is chosen to achieve the realistic numerical results. Mohr-Coulomb nonlinear material model is used for the rockfill materials and foundation in the seismic analyses. Moreover, Drucker-Prager nonlinear material model is considered for the concrete slab to represent the nonlinearity of the concrete. The dam body, foundation and concrete slab constantly interact during the lifetime of the CFRDs. Therefore, the special interface elements are defined between the dam body-concrete slab and dam body-foundation due to represent the interaction condition in the 3D model. Free field boundary condition that was used rarely for the nonlinear seismic analyses, is considered for the lateral boundaries of the model. In addition, quiet artificial boundary condition that is special boundary condition for the rigid foundation in the earthquake analyses, is used for the bottom of the foundation. The hysteric damping coefficients are separately calculated for all of the materials. These special damping values is defined to the FLAC3D software using the special fish functions to capture the effects of the variation of the modulus and damping ratio with the dynamic shear-strain magnitude. Total 4 different reservoir water heights are taken into account in the seismic analyses. These water heights are empty reservoir, 50 m, 100 m and 130 m (full reservoir), respectively. In the nonlinear seismic analyses, near-fault and far-fault ground motions of 1995 Kobe earthquake are used. According to the numerical analyses, horizontal displacements, vertical displacements and principal stresses for 4 various reservoir water heights are evaluated in detail. Moreover, these results are compared for the near-fault and far-faults earthquakes. The nonlinear seismic analysis results indicate that as the reservoir height increases, the nonlinear seismic behaviour of the dam clearly changes. Each water height has different seismic effects on the earthquake behaviour of Ilısu CFR dam. In addition, it is obviously seen that near-fault earthquakes and far field earthquakes create different nonlinear seismic damages on the nonlinear earthquake behaviour of the dam.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.846-853
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• 2006

In this study, quantitative sensitivity analysis on rockfill material influencing the dam crest displacement of Concrete-Faced Rockfill Dam(CFRD) was carried out. The purpose of this study is to indicate the most important input parameter and to show the quantitative variation of displacement at the crest of CFR type dam with this input parameter. The rockfill material properties for parametric study were obtained from the results of large scale triaxial tests on 34 rockfill materials in the 22 different sites. From the statistical analysis on these data, some statistical characteristics of rockfill material properties such as property range, distribution characteristics, and correlation between the properties were investigated. based on these characteristics, 27 property combinations were constituted by Latin Hypercube sampling method. Dam crest displacements after construction, impounding, and earthquake loading were evaluated by static and dynamic numerical analysis on each combination. From the sensitivity analysis, it was found that the crest displacement of CFR type dam was absolutely affected by the shear modulus of rockfill material and the effect of friction angle of it was negligible. This relative difference of sensitivity was more outstanding in case of crest settlement than in case of crest horizontal displacement. Also, it was found that the settlement and horizontal displacement of dam crest logarithmically decreased as the shear modulus increased and the difference between the maximum value and the minimum vale amounted to about 9.5 times in case of settlement and about 10 times in case of horizontal displacement.

• Geomechanics and Engineering
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• v.17 no.2
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• pp.119-131
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• 2019

Time dependent creep settlements are one of the most important causes of material deteriorations for the huge water structures such as concrete faced rockfill dams (CFRDs). For this reason, performing creep analyses of CFRDs is vital important for monitoring and evaluating of the future and safety of such dams. In this study, it is observed how changes viscoplastic behaviour of a CFR dam depending the time. Ilısu dam that is the longest concrete faced rockfill dam (1775 m) in the world is selected for the three dimensional (3D) analyses. 3D finite difference model of Ilısu dam is modelled using FLAC3D software based on the finite difference method. Two different special creep material models are considered in the numerical analyses. Wipp-creep viscoplastic material model and burger-creep viscoplastic material model were rarely used for the creep analyses of CFRDs in the last are taken into account for the concrete slab and rockfill materials-foundation, respectively. Moreover, interface elements are defined between the concrete slab-rockfill materials and rockfill materials-foundation to provide interaction condition for 3D model. Firstly, dam and foundation are collapsed under its self-weight and static behaviour of the dam is evaluated for the empty reservoir conditions. Then, reservoir water is modelled considering maximum water level of the dam and time-dependent creep analyses are performed for maximum reservoir condition. In this paper, maximum principal stresses, vertical-horizontal displacements and pore pressures that may occur on the dam body surface during 30 years (from 2017 to 2047) are evaluated in detail. According to numerical analyses, empty and maximum reservoir conditions of Ilısu dam are compared with each other in detail. 4 various nodal points are selected under the concrete slab to better seen viscoplastic behaviour changes of the dam and viscoplastic behaviour differences of these points during 30 years are graphically presented. It is clearly seen that horizontal-vertical displacements and principal stresses for maximum reservoir condition are more than the empty reservoir condition of the dam and significant pore pressures are observed during 30 years for maximum reservoir condition. In addition, horizontal-vertical displacements, principal stresses and pore pressures for 4 nodal points obviously increased until a certain time and changes decreased after this time.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.410-415
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• 2009

With the implementation of electric power industry reform, the utilities are looking for effective ways to improve the economic efficiency. One area in particular, the equipment maintenance, is being scrutinized for reducing costs while keeping a reasonable level of the reliability in the overall system. Here the conventional RCM requires the tradeoff between the upfront maintenance costs and the potential costs of losing loads. In this paper we describe the issues related to applying so-called the "Reliability-centered Maintenance" (RCM) method in managing electric power distribution equipment. The RCM method is especially useful as it explicitly incorporates the cost-tradeoff of interest, i.e. the upfront maintenance costs and the potential interruption costs, in determining which equipment to be maintained and how often. In comparison, the "Time-based Maintenance" (TBM) method, the traditional method widely used, only takes the lifetime of equipment into consideration. In this paper, the modified Markov model for maintenance is developed. First, the existing Markov model for maintenance is explained and analyzed about transformer and circuit breaker, so on. Second, developed model is introduced and described. This model has two different points compared with existing model: TVFR and nonlinear customer interruption cost (CIC). That is, normal stage at the middle of bathtub curve has not CFR but the gradual increasing failure rate and the unit cost of CIC is increasing as the interruption time is increasing. The results of case studies represent the optimal maintenance interval to maintain the equipment with minimum costs. A numerical example is presented for illustration purposes.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.611-616
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• 2002

The concrete beam is quickly required to be replaced or strengthened due to decreasing load carrying capacity. Flexural tests on 3.1m long reinforced concrete beams with carbon-fiber rod are reported. The selected experimental variable is the method of the anchoring beam. The effects of this variable in overall behavior are discussed. This paper considered relation of load-displacement and load-strain. The maximum load was increased to the static behavior of the R/C beam strengthened with CFR rod. The results indicated generally that the flexural strength of strengthening beam was increased. It was required a proper anchorage system and can be led the ductility of beams of a carbon-fiber rod.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.2
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• pp.9-15
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• 2010

US NRC issued rulemaking of 10CFR50.55a to perform the Perservice and Inservice inspection for Reactor Vessel Head Penetration Nozzle of US Nuclaer plant. The rulemaking was required the EPRI Demonstration to verify the NDE technique performing special Ultrasonic examination. In order to meet this requirement, the UT and ECT procedures was demonstrated and the NDE personnel were qualified by EPRI. In this paper, the NDE technique and analysis method are described the Preservice inspection for the Palo Verde #1/2/3 Replacement Reactor Vessel Head Penetration Nozzle using the qualified procedures and personnel.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.3
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• pp.79-89
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• 2011

Since commercial operation of Kori-1 nuclear power plant in 1978, twenty units are under operation and six units are under construction at 2011 present. Nuclear power become a main energy source in our country. However, the plant was constructed by a USA vendor in its beginning period, the Quality Assurance requirements of USA was applied. Even though Quality Assurance requirements were newly established to the Korea Atomic Energy Act, its contents are quite similar to those of USA. And 10 CFR 50 App.B, ASME NQA-1 apply to most of nuclear industries as a quality assurance plan. In this paper, Quality Assurance requirement of domestic nuclear industries has been investigated and applicable method of ISO Quality Assurance application to the nuclear industries is suggested by a comparison ISO 9000 and nuclear quality assurance specification.