• Magazine of the Korea Concrete Institute
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• 제9권6호
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• pp.185-193
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• 1997

본 연구는 각종 제진재료를 이용하여 진동을 억제할 수 있는 콘크리트를 개발하여 각종 건설공사에서 흔히 발생할 수 있는 진동공해문제를 억제하고자 하며 아울러 폐기물의 재활용차원에서 폐자재를 이용하여 유용한 제진콘크리트를 개발하고자 하는데 그 목적이 있다. 우선, 제진재료를 이용한 압축강도 (200kg/$\textrm{cm}^2$)이상의 콘크리트 배합비를 찾기 위하여 24배치의 예비실험을 수행하였으며, 선정된 적정배합비에 따른 제진재료를 이용한9개의 진동시험체보를 제작하여 보의 구조적 및 재료적 동적특성 즉 1차 공명진동수와 동적 휨강성 및 감쇠비를 측정하여 제진효과를 조사하였다. 그리고 압축강도에 의한 각 시험체의 균열모멘트를 추정하여 재하하중과 균열모멘트비(M/Mcr)에 따른 하중단계별 동적특성값을 살펴보았다. 제진재료로서는 라텍스(Latex), 고무분말(Rubber Powder)그리고 플라스틱 레진( Plastic Resin)등을 사용하였고, 재료적, 구조적 진동감쇠효과를 파악하고자 KS F2437규정과 진동파의 속도법을 사용하였으며, 감쇠비 측정은 Frequency Spectrum 곡선에 대한 Polynomial Curvefitting 방법과 기하학적 해석방법을 이용하여 각각의 결과를 비교.분석하였다.

• Journal of the Society of Disaster Information
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• 제18권4호
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• pp.930-935
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• 2022

Purpose: The purpose of this study is to evaluate the stiffness reduction and damping ratio of reinforced concrete hollow slabs and to analyze their performance, and to study the effect of the damping effect of hollow bodies and the stiffness reduction on the serviceability of slabs. Method: Test specimen was made in a size of 0.6m^*0.21m^*3.6m to evaluate the vibration effect of the slab, and the hollow ratio was set in six steps from 0.0% to 30% to measure the change in rigidity and damping according to the change in the hollow ratio. Result: As the hollow ratio increases, rigidity decreases and the natural frequency decreases, but as the mass decreases, the natural frequency increases gradually. Since energy is hardly dissipated up to the hollow ratio of 20%, the hollow ratio should be reduced by 30%. Conclusion: It was found that the bending strength degradation of the slab with a hollow ratio of about 30% is minimized, but an appropriate natural frequency can be maintained, and a certain damping effect can be obtained.

• Journal of Sericultural and Entomological Science
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• 제25권2호
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• pp.44-50
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• 1984

The effects of sodium pyrophosphate, sodium tripolyphosposphate and ethylene diamine tetraacetic acid as a degumming aid reagent were investigated under the conditions of underground water and dimineralized water for the scouring water sources. The changes of water qualities by adding the condensed sodium phosphates and the physical properties of scoured silk fabric were examined, respectively. 1. The water hardness of underground water was decreased by adding the condensed sodium phosphates and it was further reduced according to the increasing temperature. The water hardness reducing power of sodium pyrophosphate was a little stronger than that of sodium tripolyphosphate. 2. The sodium silicate as an alkaline reagant for scouring decreased the water hardness, but the sodium carbonate increased it in the underground water. 3. The pH value of 0.4% soap and 0.25% sodium silicate mixed solution after boiling was. 9.80, but it was leveled upto 9.90 by adding 0.05% sodium pyrophosphate and upto 9.95 by 0.02% ehtylene diamine tetraacetic acid, respectively. 4. The masking action of Fe$\^$3+/ ions dissolved in the scouring water was more remarkable by ethylene diamine tetraacetic acid than by the condensed sodium phosphates. Of the condensations, sodium tripolyphosphate was more effective than sodium pyrophosphate in the action. 5. Genrally, the dimineralized water scouring increased the boil-off ratio with reducing the flexural rigidity of fabric which was negatively related with the favorablility of hand-touch more than the underground one did. 6. Under the underground water scouring, the addition of ethylene diamine tetraacetic acid increased the boil-of ratio and compressive elasticity of fabric with reducing the flexural rigidity more than that of the condensed sodium phosphates did. 7 The additions of sodium tripolyphosphate and ethylene diamine tetraacetic acid reduced the flexural rigidity of fabric with raising the boil-off ratio even in the dimineralized water scouring, but there was no sifnificant difference between both of them.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제14권6호
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• pp.1299-1308
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• 1994

This paper is considered on the dynamic behavior and the dynamic impact coefficient on the cable-stayed bridge under the vehicle load. The method of static analysis, that is, the transfer matrix method is used to get influence values about displacements, section forces of girder and cable forces. Gotten influence values were used as basic data to analyse dynamic behavior. This paper used the transfer matrix method because it is relatively simpler than the finite element method, and calculating speed of computer is very fast and the precision of computation is high. In the process of dynamic analysis, the uncoupled equation of motion is derived from simultaneous equation of the motion of cable-stayed bridge and vehicle travelling by using mode shape, which was borne from system of undamped free vibration. The solution of the uncoupled equation of motion, that is, time history of response of deflections, velocity and acceleration on reference coordinate system, is found by Newmark-${\beta}$ method, a kind of direct integral method. After the time history of dynamic response was gotten, and it was transfered to the time history of dynamic response of cable-stayed bridge by linear transformation of coordinates. As a result of this numerical analysis, effect of dynamic behavior for cable-stayed bridge under the vehicle load has varied depending on parameter of design, that is, the ratio of span, the ratio of main span length, tower height, the flexural rigidity of longitudinal girder, the flexural rigidity of tower, and the cable stiffness, investigated. Very good agreements with the existing solution in the literature are shown for the uncracked plate as well as the cracked plate.

• Proceedings of the KSR Conference
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.641-646
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• 2009

Concrete tracks are superior to ballast tracks in the aspect of durability, maintenance and safety. However, deteriorated stiffness of railroad bed and settlement of soft ground induced by trapped or seepage water lead to problems in safety of train operation. In this research, characteristic stiffness of concrete tracks, which is determined from FRACTAL (Flexural-Rigidity Assessment of Concrete Tracks by Antisymmetric Lamb Waves) technique, was employed as an index of track displacement. The characteristic stiffness is defined using Poisson's ratio, moment of inertia and stiffness ratio of subgrade to slab. To verify validity and reliability of the proposed characteristic stiffness, experimental and theoretical researches were performed. Feasibility of the characteristic stiffness based on FRACTAL technique was proved at a real concrete track for Korean high-speed trains. Validity of the FRACTAL technique was also verified by comparing the results of impulse-response tests performed at the same measurement array and the results of SASW tests and DC resistivity survey performed at a shoulder nearby the track.

• Structural Engineering and Mechanics
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• 제86권4호
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• pp.503-518
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• 2023

In tall constructions, the outriggers are regarded as a structural part capable of effectively resisting lateral loads. This study analyses the efficacy of hybrid outrigger system in high rise RCC building for various structural parameters identified. For variations in α, which is defined as the ratio of the relative flexural stiffness of the core to the axial rigidity of the column, static and dynamic analyses of hybrid outrigger system having a virtual and a conventional outrigger at two distinct levels were conducted in the present study. An investigation on the optimal outrigger position was performed by taking the results from absolute maximum inter storey drift ratio (ISD_max), roof acceleration (acc_roof), roof displacement (disp_roof), and base bending moment under both wind and seismic loads on analytical models having 40, 60 and 80 storeys. An ideal performance index parameter was introduced and was utilized to obtain the optimal position of the hybrid outrigger system considering the combined response of ISD_max, acc_roof, disp_roof and, criteria required for the structure under wind and seismic loads. According to the behavioural study, increasing the column area and outrigger arm length will maximise the performance of the hybrid outrigger system. The analysis results are summarized in a flowchart which provides the optimal positions obtained for each dependent parameter and based on ideal performance index which can be used to make initial suggestions for installing a hybrid outrigger system.

• Journal of the Korea institute for structural maintenance and inspection
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• 제17권2호
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• pp.54-61
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• 2013

Stay cable has a strong axial rigidity due to large initial tension and, on the other hand, it has a weak laterally flexural rigidity. Wind loads or traffic loads cause the cables to vibrate significantly and affect the mechanical properties and the performance of cables of cable-stayed bridge (CSB). Therefore, the development of vibration reduction design is an urgent task to control the vibration vulnerable long-span bridges. As Friction damper (FD) shows to reduce the amplitude and duration time of vibration of cable of CSB from measured date in field test, friction damper can be considered that it is effective device significantly to reduce the amplitude and duration time in vibration of cable of CSB under traffic load, wind load and so on. Vibration characteristics of cable can change according to manufacturing method and type of established form. Nevertheless, analysis method in this study can present the design of friction damper for vibration reduction of cable of cable-stayed bridge from now on.

• Journal of the Korea Concrete Institute
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• 제13권6호
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• pp.584-592
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• 2001

The cracks are developed in reinforced concrete(RC) beams at the early stage of service load because of the relatively small tensile strength of concrete. The structural strength and stiffness are decreased by reduction of tensile resistance capacity of concrete due to the developed cracks. Using the fiber reinforced concrete that is increased the flexural strength and tensile strength at tensile part can enhance the strength and stiffness of concrete structures and decrease the tensile flexural cracks and deflections. Therefore, the RC beams used of the fiber reinforced concrete at. tensile part ensure the safety and serviceability of the concrete structures. In this work, analytical model of a dual concrete beams composed of the normal strength concrete at compression part and the high tension strength concrete at tensile part is developed by using the equilibrium conditions of forces and compatibility conditions of strains. Three groups of test beams that are formed of one reinforced concrete beam and two dual concrete beams for each steel reinforcement ratio are tested to examine the flexural behavior of dual concrete beams. The comparative study of total nine test beams is shown that the ultimate load of a dual concrete beams relative to the RC beams is increased in approximately 30%. In addition, the flexural rigidity, as used here, referred to the slope of load-deflection curves is increased and the deflection is decreased.

• Journal of the Korean Society of Clothing and Textiles
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• 제19권3호
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• pp.471-482
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• 1995

Using the acetate velvet and viscose velvet whose pile lengths were sheared as 1.45, 1.55, 1 65, 1.75, 1.85, 1.90mm under the condition equating the weaving process of ground fabric, the conclusions were as follows through the results of the sensory assessments estimated by women students in our university and the physical properties, H. V and T. H. V obtained by KES-F system. 1. In the sensory assessments estimated by the method of paired comparison and ranking of samples, the longer pile length was, the more the hand values of smoothness, softness, thickness, heaviness increased on the whole. 2. The H V. and T. H. V. measured by KES-F system were as follows; Kohi increased to pile length 1.85mm and then decreased a little at 1.90mm. hummer increased as pile length was longer. Fukurami increased to pile length 1.75mm and then decreased gradually as pile length was longer. Total hand value increased gradually from 1. 45mm to 1.85mm, had the top value at 1.85mm, and then decreased a little at 1.90mm. 3. In the results of summarizing $\ulcorner$the physical properties correlated closely with the H. V obtained by sensory assessments$\lrcorner$ and tithe Physical properties correlated closely with the H. V. and T. H. V obtained by KES-F systems, it showed that all the sensory properties correlated closely with compressive energy, flexural rigidity, thickness, weight and pile ratio in the former and that the physical properties correlated closely with each H V and T. H. V were different in the latter. 4. It showed that factor 1 was related to compressive energy, thickness, weight, pile ratio, factor 2 was related to recovery energy, compressive resilience, compressive index, and factor 3 was related to compressive recovery ratio in the result of factor analysis. 5. In the multiple repression analysis, the expressions of all sensory properties had compressive ratio, frictional coefficient in the regression expressions of $\ulcorner$H. V. obtained by sensory assessments$\lrcorner$, while the expressions of each H. V. and different physical properties in the regression expressions of $\ulcorner$H. V. obtained by KES-F system$\lrcorner$.

• Magazine of the Korean Society of Agricultural Engineers
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• 제44권1호
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• pp.93-102
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• 2002

Steel fiber and polymer are used widely for reinforcement material of RC structures because of its excellences of the durability, serviceability as well as mechanical properties. The purpose of this study is to investigate the shear behavior of polymer cement high strength concrete beams mixed with steel fiber. The compressive strength of concrete was based on the 100$\times$200 mm cylinder specimens. The compressive strength of concrete are 320$kgf/cm^2$, 436 $kgf/cm^2$ and 520 $kgf/cm^2$ in the 28 days. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns and fracture modes. Also, load-strain and load-deflection examined. During the test cracks were sketched against the load values according to the growth of crack. result are as follows; (1) The failure modes of the specimens are increased in rigidity and durability with mixing steel fiber and polymer. (2) The load of initial crack was similar a theory of shear-crack strength. (3) The deflection and strain at failure load of Polymer-steel fiber high strength concrete beams were increased, improving the brittleness of the high strength concrete.