• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.411-423
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• 2008

Pneumatic vibration isolator has a wide application for ground-vibration isolation of vibration-sensitive equipments. Recent advances In precision machine tools and instruments such as nano-technology or medical devices require a better isolation performance, which can be efficiently done by precise modeling- and design- of the isolation system. This paper will discuss an efficient transmissibility design method for pneumatic vibration isolator by employing the complex stiffness model of dual-chamber pneumatic spring developed in our previous research. Three design parameters of volume ratio between the two pneumatic chambers, the geometry of capillary tube connecting the two pneumatic chambers and finally the stiffness of diaphragm necessarily employed for prevention of air leakage were found to be important factors in transmissibility design. Based on design technique that maximizes damping of dual-chamber pneumatic spring, trade-off among the resonance frequency of transmissibility, peak transmissibility and transmissibility in high frequency range was found, which was not ever stated in previous researches. Furthermore this paper will discuss about negative role of diaphragm in transmissibility design. Then the design method proposed in this paper will be illustrated through experiment at measurements.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.162-162
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• 2011

표면파 속도 측정은 근래 토목분야에서는 비파괴 지반조사기법으로 활용되고 있다. 최근에는 디지털 신호처리기술의 발달과 함께, 더욱 정확해진 자료분석 알고리즘을 통하여 표면파 탐사관련 기술이 향상되어 3차원의 공간연속적인 시험이 가능해졌다. 본 연구는 표면파의 분산 특성을 이용하여 콘크리트 구조물의 깊이별 강성평가를 하는 SASW(Spectral Analysis of Surface Waves)기법과 STFT(Short time Fourier Transform)과 HWT(Harmonic Wavelet Transform)를 이용한 주파수영역에서의 공진주파수를 통한 부재평가 기법인 IE(Impact Echo)기법을 이용하여 대상부재의 강도평가를 수행하기 위한 시제품 개발을 수행하였다. 시제품은 메인프레임과 2개의 센서로 이루어져 측정을 수행하며 측정장치와 DAQ장치 및 S/W로 구성되어 있다. 메인프레임의 진동특성영향을 제거하기 위하여 2개의 센서는 프레임과 띄움구조로 설계하였고 센싱하는 위치는 대상 재료의 밀착되어 계측할 수 있도록 설계하였다. 탄성파를 계측하여 대상 재료의 깊이별 측정된 표면파의 속도를 계측하며 개발된 시제품의 구조물별 적용성 평가를 위한 실험을 수행하였고 평균 표면파 속도를 통해 추정한 콘크리트 두께와 결함 및 강도 추정의 적용성을 평가하였다. 시제품을 이용해 시험콘크리트 표면파를 측정한 결과 SASW기법을 이용하여 깊이에 대한 위상속도 분포와 IE기법의 결과로 개발된 시제품의 합리적 적용성이 평가되었다. 그러나 재료의 강도추정에 있어서는 각각 알고리즘의 주파수분석 요소들에 의해 변동되는 경향을 보여 추후 많은 테스트를 통해 속도-강도 추정의 회귀곡선식을 S/W에 탑재시키고 다양한 방법으로 조합하는 알고리즘으로 신뢰성있는 강도추정을 위한 알고리즘을 개발하여야 한다.

• Journal of the Korean Society for Railway
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• v.12 no.6
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• pp.835-843
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• 2009

Recently the more stable roadbed is required due to the high speed and design load. Therefore the reinforced roadbed was introduced as the solution. But the thickness and stiffness of reinforced roadbed in design code is being conservatively assessed by the foreign code without considering the domestic construction condition. In this paper, adequate Young's modulus, drain capacity, freezing depth, economical efficiency, bearing capacity, construction condition and 3-D finite element method were employed to determine the proper thickness of reinforced roadbed at the embankment section.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.887-890
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• 2008

Shindorim Station is the most important transfer station which is crossed Seoul Metro Line-2 and national rail traffic Kyungbu, Honam and Kyungin Line etc.. There is the lagest transfer passengers and the greatest rail traffic. Therefore to solve the congeted station problem, Shindorim station extension project has been planned. This project has very difficult many problems. One of them is undercrossing the national rail traffic ground without open-cut excavation. There are many undercrossing construction methods in our country. But this project is required the best safety. So the best applicable methods are investigated, which are Front-Jacking, NTR and TRcM. In Design stage Front-Jacking with PRS method which is gound reinforcing is applied.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.223-234
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• 1993

The main characteristics of PHC piles is that silica material and autoclave curing technique are used when manufacturing to have higher strength than PC piles. In this paper, pile drivability and bearing capacity characteristics of the PHC piles are studied through numerical analysis based on wave propagation theory, driving records and pile load tests in situ. It is found that we can have higher bearing capacity by using the PHC piles rather than the PC on condition that the most effective driving equipment is chosen when driving the pile. In other words, since the PHC piles have higher resistance to driving energy, the heavier ram can be used in the driving process, which results in the higher bearing capacity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1091-1096
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• 1994

Since horizontal movements due to shrinkage and thermal gradients in concrete pavements involve no actual load, the stresses induced will be those due to closing of the pavement joints and subbase friction. Consequently, complete derivations of stiffness matrix and equivalent nodal loads due to planar effects on the concrete pavements was throughly undertaken using the finite rectangular elements with two degrees of freedom at each node. The numerical example shows that the tensile stress induced in a pavement due to concrete shrinkage might be negligible except at very long slab and very high coefficient of frictions. However the stresses in conjunction with principal traffic loads might cause cracking problems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.04a
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• pp.148-153
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• 1994

각종 산업 플랜트엣 입형펌프의 공진문제는 다른 기계에 비해 자주 발생한다. 이는 입형펌프가 구조 특성상 대개 지반에 비해 기초강성이 낮은 콘크리이트 슬래브(slab)위에 설치되는 경우가 많고, 외팔보 형태의 펌프 위에 무거운 전동기가 설치되어 무게 중심이 횡형펌프에 비해 높게 되기 때문에 대형 입형펌프 구조물의 고유진동수는 낮게 된다. 그리고, 일반 대형펌프의 회전주파수도 저속임에 따라 축계의 불평형가진력에 의한 공진문제가 빈번하게 발생된다. 대형 입형펌프가 설비가동에 있어서 최중요 기계(critical machine)인 경우가 대부분이므로 높은 진동을 유발시키는 공진은 공장 설비운전의 안정성에 큰 영향을 미친다. 입형펌프의 전동기가 아무리 밸런싱 상태가 좋고, 설치상태가 펌프 전동기제작사의 설치조건을 만족한다 하더라도 전도이가 펌프위에 설치되어 운전될 경우 공진이 발생하게 되면 과도한 진동이 일어나게 된다. 이때 전동기에 부하가 걸리지 않는 전동기 단독운전 상태에서도 높은 진동이 나타나기 때문에 운전자는 흔히 전동기자체의 문제로 판정하곤 한다. 이같은 현상은 보통 진동원인이 전동기에 있지 않고 펌프의 전동기대(motor stool)와 전동기 시스템의 리드 공진(reed resonance)에 의한 결과이다. 본 논문에서는 입형 펌프에서 리드공진의 확인방법과 대책작업에 대해 실제 사례를 통하여 논한다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.7 s.112
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• pp.777-783
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• 2006

In this study, quantitative ground vibration values and damping coefficient produced by underwater blasting were measured and analyzed. Also, hydrospace noise in aquafarm and noise in atmosphere as well as ground vibrations were measured, and maximum values of these results were 86,8 dB(A), 147,8dB(A), 0.244 cm/s, respectively, With these results, vibration influence about snakehead (channa argus) and structures were examined. the damage of those was proved that is not. Equations of vibration ($V_{50%}=1.507SD^{-0.536},\;V_{95%}=2,171SD^{-0.536}$) and hydrospace noise ($SL=293.2SD^{-0.164}$) were presented from quantitative experiment results. respectively. 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.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.4
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• pp.299-306
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• 2011

This study investigated the SIP-method as a low-vibration, low-noise engineering method. The ground vibrations caused by the SIP-method were measured and analyzed in each step. From the analysis results, quantitative ground vibration values and reliable vibration estimation equations were proposed. Furthermore, the ground vibrations caused by the SIP-method were compared with the ground vibrations caused by other methods presented by existing studies. Based on the vibration estimation equation with 50 % reliability, the ground vibration values by the SIP-method at the distance of 10~150 m corresponded to 17~57 % of the ground vibration values by the equation proposed by Attewell & Famer, and 14~96 % of the ground vibration values by the equation proposed by Prof. Park in his study using a diesel drop hammer. These results showed that the ground vibration reduction effect of the SIP-method was higher those of other general engineering methods. Finally, the permissible scope of work using the SIP-method which meets the domestic vibration standards was presented.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.2
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• pp.39-52
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• 1987

This study was to investigate the effects of soil-structure relative stiffness on the structural characteristics of the cylindrical tank supported by soil. A standard example model of the farm silo rested on the Winkler's subsoil model was used for the analysis of soil-structure coupled system. In this paper, Winkler's constants 4,15 and l00kg/cm$^2$/cm were considered and the bottom plate thicknesses of the farm silo 20, 30, 50,100 and 150cm were adopted. For the given model the effects of bottom plate thickness were the most conspicuous at weakest Winkler's constant 4kg/ cm$^2$/cm. While when Winkler's constant is l00kg/cm$^2$/cm, the effect of the bottom plate thickness is almost negligible. On the other hand, when the bottom plate thickness is more than 100cm, the effects of elastic foundation were aknost disappeared. In design practice, it is hoped that the thicknesses of bottom plate should be determined reasonably because of it's considerable effect on the structural characteristics as the lOOcm thickness of bottom plate will not be practical value in usual sites.