• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.117-127
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• 2012

As increasing number of large-size earthquake around Korean peninsula, many interests have been focused to the earthquake strengthening of existing structures. Fiber reinforced plastic composite material is one of strengthening material widely used to increase seismic performance of structures. It should have high stiffness as well as large ductility to provide best strengthening result. Thus selection of stiffener and fiber in composite is of important. In this study, the optimal combination of fiber and stiffener is selected with variety of tensile tests. In order to investigate performance of chosen composite material, several finite element analyses are performed with proposed FRP composite material for existing RC columns. It is discussed that the seismic performance of strengthened columns through the load-displacement relationship. It is shown that the proposed composite material can increase the strength as well as ductility of exiting RC columns.

• Composites Research
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• v.28 no.4
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• pp.148-154
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• 2015

In order to detect damage in early stages and properly maintaining structures, the structural health monitoring technology is employed. In most cases, active-sensing SHM needs many piezoelectric (PZT) sensors and actuators. Thus, if there is a defect on PZT used for active-sensing SHM, the structural status could be misclassified. This study, for reliable SHM performance, investigated to detect defects of sensors by using the admittance-based sensor diagnostics. This study also introduced an algorithm that can diagnose sensor defects based only on data measured from the sensors in case that information about the changes in adhesive and environmental investigation, this study confirms that the proposed algorithm could be efficiently applied to real-world structures in which a significant temperature variation could take place.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.142-152
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• 2010

In this study, eleven reinforced concrete beams, without stirrup, using high ductile fiber-reinforced mortar with ground granulated blast furnace slag(SHF Series, SHFSC Series) and standard specimens without or with stirrup(SSS, BSS) were constructed and tested under monotonic loading. Experimental programs were carried out to improve and evaluate the shear performance of such test specimens, such as the load-displacement, the failure mode, the maximum strength, and shear strength. All the specimens were modeled in scale-down size. Test results showed that test specimens(SHF Series, SHFSC Series) was increased respectively the shear strength carrying capacity by 26%, 20% and the ductility capacity by 5.27, 5.75 times in comparison with the standard specimen without stirrup(SSS). And the specimens(SHF Series, SHFSC Series) showed enough ductile behavior and stable flexural failure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.59-65
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• 2024

In this study, in order to improve the mechanical properties and durability of asphalt mixtures, a modifier (CSM, Cationized Silicate Modifier) was applied to asphalt to derive optimal mixing ratio conditions. Design of asphalt mixture using modified asphalt binder was conducted, and moisture resistance and dynamic stability were evaluated for optimal mixing conditions. The evaluation results showed that it exceeded the standards stipulated in the relevant guidelines, and as a result of conducting a water permeability test on the optimal mixing condition, it was confirmed that impermeable performance was secured. As a result of examining the noise reduction performance through field test, a noise reduction performance of about 10 dB was secured compared to before paving. It will be necessary to secure reliability through continuous noise generation evaluation in the future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.123-132
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• 2008

Aseries of in-situ tests and ground water level measurements with stone and slug materials had been conducted to find out effect of ground settlement reduction and bearing capacity improvement by the Stone Column method. As the result of the tests, it was proved that the Stone Column method is effective for reduction of ground settlement and improvement of bearing capacity. In addition the ground water level went down without overburden load. These results show that the Stone Column method is effective for an increase in density and resistance to liquefaction. The results of estimation of ground settlement and bearing capacity by general theoretical equation, it show that the Stone Column method increases bearing capacity by 2.7~5.7 times and decreases ground settlement by 2~3.5 times.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.2
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• pp.70-76
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• 2009

This paper introduces an evaluation code, which can numerically express the noise possessing degree of signals. By using this code, the best kind and setting of noise suppressing techniques can be chosen automatically. This code is applied to three kinds of specific denoising techniques; those are simple noise removing method in the count versus phase distribution, fuzzy logic method based on noise type in magnitude versus phase plot, and lastly, the technique using grouping characteristics of PD pulses in 3D plot of magnitude versus phase versus cycle. The algorithm shows good performance in the various real PD signals measured from various high voltage apparatuses in Korea.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.100-109
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• 2011

Recently, the concrete-steel hybrid extradosed bridge has been proposed as alternative bridge type at long span site. The hybrid extradosed bridge adopts light orthogonal deck girder instead of heavy concrete deck girder at the center span of bridge, and it enables to construct long-span bridge. And also, for this bridge type the decrease of self-weight of girder enables to reduce girder depth and side span length of extradosed bridge, so its type has more efficient structural behavior and makes it possible to perform optimal bridge design. Therefore, it is very important to set up the procedure and parameters of optimal design for concrete-steel hybrid extradosed bridge. In this study, the effects of design parameters (the variation of pylon height, bridge deck depth and orthogonal deck girder length) are discussed. And numerical analysis and sensitivity analysis are carried out according to these parameters. And design weight values about these parameters are quantitatively suggested to reflect characteristics of concrete-steel hybrid bridge.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.55-63
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• 2012

This paper presents materials and processing technique to manufacture low viscous strain-hardening cementitious composite which is suitable for structures requiring low viscosity of materials. The micromechanics and fracture mechanics tools coupled with processing techniques were adopted to achieve low viscosity of composites as well as high tensile strain capacity. Optimal volume and length of fibers and interfacial properties between fibers and matrix for composites with tensile strength of 2~3MPa were determined on the basis of the micromechanical analysis and the steady-state cracking theory. Then six mixtures were determined and the experiment was carried out to evaluate the viscosity and uniaxial tensile performance of those. From the test results, it is verified that the strain-hardening cementitious composite with low viscosity suitable for grouting applications in fresh state as well as high ductility over 1.5% in hardened state can be feasible.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2
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• pp.92-100
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• 1995

In this study, the bearing defects were modeled and the vibration of ball bearing faults was presented for the defective pattern. The vibration signal was measured for the single and multiple defected ball bearing at the various defect positions and rotation speed, and then the signal components using the HFRT(high frequency resonance technique) were analyzed by FFT. The experimental data analysis has shown that the frequencies generated in the single or multiple defected ball bearings appear with the characteristic defect frequency and harmonics of ball pass frequency peak. Signal processing by HFRT makes it possible not only to detect the presence of a defect but also to diagnose the defect part of the bearing.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.87-96
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• 2004

As a special concrete, which is a mixture of soil, cement and water, has strength like regular concrete for pavement, soil cement has been used in various field such as pavement and soft soil improvement. The objective of this study was to investigate the characteristic of unconfined compressive strength and time dependent behavior of soil cement that is made from decomposed granite soil or coluvial and inorganic solidification liquid. The results showed that the unconfined compressive strength appears to increase as the amount of cement and curing time increase In addition, the strength seems to decrease with increase of the potion of fine particles(No 200 sieve). The result of XRD indicated that there is Vermiculite, the product of reaction, in the soil cement. The dynamic properties of material, such as shear complex compliance, shear complex modulus, and phase angle could be calculated from the hysteresis loop obtained from the Haversine Creep Tests. Finally, creep behavior was able to be predicted from these dynamic properties.