• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.3
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• pp.185-191
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• 2007

For the seismic performance enhancement of residential flat plate structure and for the selection of earthquake records, the possibility of base isolation is evaluated and the time history results are reviewed. By evaluating a base isolated stiffness, a target period, and an envelope curve analysis, seismic performance of structure, which has strong rotational mode, is evaluated. For the propriety evaluation of earthquake records usage and scaling method, time history analysis is done with variables such as DBE(design base earthquake) level, MCE(maximum considerable earthquake) level, and 1.4DBE level. From the analysis results, following conclusions can be made; the earthquake records, which are used in base isolation analysis, should be selected by similar soil type which the structure is considered, and should be intensity scaled in a range of mean ${\pm}$ standard deviation of code based design response spectrum.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.163-170
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• 2007

To evaluate on the applicability of Chemical Compaction Pile (CCP) method to weak soil improvement, two kinds of testing chambers were fabricated and the changes of water content and shear stress associated with soil types, ages and distances from the center of pile were measured with different mixing proportions of CCP such as bottom ash, lime powder and added admixture. As results of test, it was noted that water content and shear stress of ground are mainly affected by the amount of lime powder and increase of the amount corresponds to rapid improvement of soil. And the improvement depended greatly on the types of soil also. It was finally found that CCP developed can be applicable to bearing pile as well as soil improvement since CCP has a bearing capacity enough to carry loads.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.193-202
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• 2008

This paper investigates experimentally the confining effect, strengthening capacity and rebound rate of sprayed Fiber-Reinforced-Polymer (SFRP). From the method, resin and chopped fibers are sprayed separately from the nozzle with high pressure, and then they are attached to the concrete surface, so structure could be repaired. To evaluate the strengthening effect of sprayed FRP, cylindrical specimens and beam specimens were strengthening with SFRP. As main material of FRP, glass fiber and polyester resin are used. To investigate the optimum condition of sprayed FRP, the effects of fiber length, coating thickness, fiber volume ratio and concrete strength were examined. Capacities of sprayed FRP method were also compared to the FRP sheet method. In case of the sprayed FRP, rebound rate is important parameter considering economical efficiency and constructibility, so rebound rate of was discussed. From the test results, optimum conditions of sprayed FRP were determined. SFRP method showed superior strengthening capacities than FRP sheet method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.114-122
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• 2007

In high strength bolted joints, the corrosion of base material causes the reduction of slip resistance of the joints. In this study, tensile tests on slip-critical joints utilizing Zn/Al metal spraying corrosion resistance method were carried out in order to prevent the corrosion and meet the required mechanical characteristics of joints. In addition, slip coefficient and surface roughness were calculated. The key parameters were surface finishing condition and thickness of coating with the identical geometry in all specimens. From the results, it is found that the slip coefficient of the joints with coated finish after sand blast treatment as well as those of non-coated joints with only sand blast treatment were similar or superior to 0.45, which is a specification criteria of slip coefficient in friction-typed joints.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.47-54
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• 2008

In this study, ground vibration values and damping coefficient produced by underwater blasting were measured and analyzed. Equations of vibration, $V=K(SD)^{-0.536}$, were presented from quantitative experiment results. The K Values are classified with 1.507, 2.005 and 2.939 respectively at 50%, 90% and 95% reliability. Also, hydrospace noise in aquafarm and noise in atmosphere as well as ground vibrations were measured, and maximum values of these results were 86.8dB(A), 147.8dB(A), 0.244cm/s, respectively. Equations of hydrospace noise, $SL=293.2SD^{-0.164}$, was presented from quantitative experiment results. Also, the flow-chart for influence estimation and underwater blast design was presented from these results. The results of the study may be applied for the evaluation of the influence on aquafarm as a basic data before having main underwater blasting at construction sites.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.119-128
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• 2008

In this study, new moment-resisting precast concrete beam-column joint is proposed for moderate seismic regions. It has the connection reinforcing bars, penetrated the joint and lap-spliced with the bottom bars of precast U-shaped PC beam. To evaluate the performance for noncontact lapped splice, experimental and analytical works were conducted. Major variables for tests are the length of lap, the diameter of connection reinforcing bars, and the distance between lapped bars. Analytic research was performed nonlinear finite element method. Analytic research focused on crack pattern, load-deflection curve, comparison of internal force, evaluation of ductility strains of reinforcement bar. Results of experimental and analytical works show that the these variables has much influence on flexural strength and ductility, and joint behavior.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.121-130
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• 2008

Recently, we can see an increasing amount of dam damage or failure due to aging, earthquakes occurrence and unusual changes in weather. For this reason, dam safety is gaining more importance than ever before in terms of disaster management at a national level. Therefore, the government is trying to come up with an array of legal actions to secure consistent dam safety. Other dam management organizations are also taking various institutional and technical measures for the same purpose. In this study, Dam Safety Management System, KDSMS, has developed for consistent and efficient dam safety management. The KDSMS consists of dam and reservoir data, a hydrological information system, a field inspection and data management system, a instrumentation and monitoring system including earthquake monitoring, a field investigation and safety evaluation system, and a collective information system. The KDSMS is a kind of enterprise management system which has been developed to deal with safety management of each field, research center, and headquarter office and their correlation as well as detailed safety information management.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.74-80
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• 2008

This paper evaluates seismic capacities of slab-column joints in flat plate system which has columns with various aspect ratio as experimental parameters. Continuous - bended shear reinforcements were applied for the prevention of punching shear failure in this study. The specimens of FIS1-05, FIS1-10, and FIS1-20 have the aspect ratio of 0.5, 1.0, and 2.0 respectively. Static lateral force was applied to the specimens in a horizontal direction and vertical load was applied by constant gravity load ratio. The test results were evaluated by lateral displacement and strength of slab-column joint. Consequently, the lateral resisting capacity of rectangular type column such as FIS1-05, FIS1-20 is superior to the square type column such as FIS1-10.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.81-90
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• 2008

This paper concerns the flexural capacity of reinforced concrete beams with ultra-high performance cementitious composites(UHPCC). It was investigated if the existing equations to estimate the flexural capacity of reinforced fiberous concrete beams are applicable with the experiments including lightly reinforced concrete beams. The reinforcing effect when the steel fiber reinforced concrete was used in beams was also estimated. The results showed that the equation to predict the flexural capacity of reinforced steel fiber concrete by ACI 544 committee didn't have a good agreement with the test results and underestimated the flexural capacity in especially lightly reinforced beams with under 1.5% reinforcement ratio. the enhancement of flexural capacity was quite considerable in lightly reinforced beams when the steel fiber reinforced concrete was used. A equation to predict the reinforcing effect of steel fiber in reinforced steel fiber beams was developed. the equation was proposed as a function of both the characteristics of steel fiber and reinforcement ratio.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.143-151
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• 2007

This study presents the experimental results of frost durability including resistance to freezing-thawing and surface scaling of concrete. Mixing design was proportioned with the various water-binder ratio between 0.37 and 0.47 and three different binder compositions corresponding to Type I cement without any supplementary cementitious materials(OPC), Type II cement with 50% blast-furnace slag replacement(BFS50), and ternary cement with Type III cement, 15% fly ash, and 35% slag replacement (BFS35%+FA15%). Test results showed that the mixing design with BFS50% and BFS35%+FA15% exhibited higher durability factor than that made with OPC only. Finally, the use of blend cement containing slag can be used effectively in terms of frost durability of the concrete exposed to severe condition under coastal environment like as flying salt, sea water spray, etc.