• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.2
• /
• pp.153-165
• /
• 2006

A damage in a structure changes its dynamic characteristics such as natural frequencies, damping ratios, and the mode shapes. In this paper the effort has been spent in obtaining the characteristics of the reduction ratio in natural frequencies and the damage detection is performed using the reduction ratios. Most of the emphasis has been on using the artificial neural network to determine the location and the extent of the damage as well as the existence of the damage. The data for learning and verifying neural network were obtained from the analytical analysis. The data have no errors. Considering the real measurements the data including errors which are difference this study between other studies also were used for neural network. The position and extent of the damage can be detected using the neural network trained by reduction ratios of natural frequencies.

• Journal of the Korea Concrete Institute
• /
• v.13 no.5
• /
• pp.423-429
• /
• 2001

In this study, strength characteristics of concrete specimens subjected to horizontal continuous vibration during initial curing were investigated. As experimental variables, vibration velocity(0.25, 0.5, 1.0, 2.0, 4.0 kine) and vibration time(3, 6, 12, 24 hrs) were used. Density and segregation of the specimens were also investigated. Vibrating was started soon after placing, and strengths investigated consist of compressive strength, splitting tensile strength, and bond strength. Strengths decrease were hardly occurred at 0.25 kine vibration velocity regardless of vibration times and all strengths were increased for 3 hrs vibration at 0.5 kine vibration velocity. Density was increased for all specimens due to the vibration and there was no serious segregation under even 4 kine vibration velocity.

• Journal of Korean Association for Spatial Structures
• /
• v.9 no.3
• /
• pp.59-66
• /
• 2009

Dynamic characteristics such as frequency and damping ratio in the ambient state of building has been progressed in domestic and foreign. However, there has not been any deep research of dynamic characteristics of full-scale structure using vibration measurement of the building damaged up to failure. Dynamic characteristics of three-story reinforced concrete building was evaluated before and after it was damaged by using a actuator. Dynamic characteristics is reviewed and compared with previous study. Ambient vibration and human excitation test were applied. After 120mm horizontal displacement by actuator, frequency of long and short direction is reduced to 34.3%, 33.7% and damping ratio is reduced to 36.5%, 19.5% respectively.

• Computational Structural Engineering
• /
• v.8 no.4
• /
• pp.173-180
• /
• 1995

Application of soil grouting method was adopted to reduce the vibration amplitude which propagates from the source. The direct formulation of the Boundary Element Method was applied to make the numerical model of soil. It was found form this study that the most effective location of the grouting layer is directly under the source of the vibration and the width of the grouting layer does not need to be longer than the required width which can be determined by numerical analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.656-661
• /
• 2001

생산 현장의 진동환경은 부품생산활동과 관련된 공정변수중 대표적인 것으로 기계 부품 생산의 품질 및 생산품의 불량률에 큰 영향을 미치며 또한 주변으로 전파된 진동은 우수한 진동환경을 요하는 다른 생산장비에 나쁜 영향을 미치기도 한다. 본 연구의 대상은 공장의 이전으로 인한 환경변화에 의해 발생한 타공형 방음벽 생산 프레스의 진동을 제어하기 위해 바닥의 진동가속도 레벨을 측정하고 DIN 5140에 제시된 기준에 적합하도록 방진 시스템을 설계하였으며 그 결과 방진전과 비교하여 약 20 ㏈ 가량의 바닥 진동 가속도 레벨이 감소하였다.

• Proceedings of the KIPE Conference
• /
• 2010.11a
• /
• pp.15-16
• /
• 2010

본 논문에서는 최소의 진동/소음을 가지는 SRM을 설계하기 위하여 고정자와 회전자의 Skew에 따른 단상 6/6 SRM의 소음/진동 특성을 비교, 분석하였다. SRM(Switched Reluctance Motor)에 발생하는 소음/진동의 주 원인은 모터 구동 시 Yoke 에 발생하는 방사방향 힘의 변화라고 할 수 있다. Yoke에 작용하는 힘은 돌극이 위치한 곳에 집중되므로 더욱 큰 진동을 유발하지만 회전자와 고정자에 동일한 Skew를 적용시키면 힘을 받는 Yoke의 면적은 늘어나게 되고, 따라서 방사방향의 힘을 요크 전체로 분산 시킬 수 있다. 이에 따라 스위치 온, 오프시 요크에 인가되는 방사방향의 힘의 최대치는 감소하게 되어 진동/소음이 현저히 줄어들게 된다. 본 논문에서는 최소의 진동/소음을 가지는 SRM을 설계하기 위하여 시뮬레이션을 통하여 회전자와 고정자의 스큐 각도에 따른 힘의 분포를 분석하였다. 시뮬레이션 결과를 바탕으로 하여 대표적인 특성을 가진 $0^{\circ}$, $18^{\circ}$의 SRM을 설계하여 소음/진동을 측정한 결과 제안한 방식이 소음/진동을 현저하게 감소시키는 효과를 가짐을 입증하였다.

• Explosives and Blasting
• /
• v.37 no.1
• /
• pp.24-33
• /
• 2019

Recently, Electronic Detonators have gradually increased their performance for various purposes such as vibration control and improved Fragmentation. This study analyzed the vibration estimation equations of electric and electronic detonator blast by comprehensive analysis of the vibration data collected during electric and electronic detonator blast waves at the comparison sites of urban areas, geology and soil conditions, stone quarries and mines in different areas of Korea from June 2017 to December 2018. It has been confirmed that electronic detonator blast can meet the criteria for allowing vibration even if maximum charge weight per delay is increased by 1.5 times compared to the electric detonator blast.

• Journal of the Society of Disaster Information
• /
• v.11 no.1
• /
• pp.89-96
• /
• 2015

To reduce noise inside an elevated railroad station, the vibration of the station structure should be lowered, and to establish more effective anti-vibration measures it is required that, reflecting the track-bridge-structure interaction, the transfer characteristics of vibration induced by a train is well identified. In this paper, the current status of domestic railroad stations is classified, and the vibration transfer characteristics is analyzed via measurement data from representative elevated stations. From the analysis results on the measurement data, in transferring vibration from the track to the structure, remarkable vibration reduction in higher frequency range is observed, and, in some stations, amplified response characteristics in lower frequency range is identified. Also, for stations with floating track system or TPS type, relatively greater reduction in transferred vibration is observed.

• Explosives and Blasting
• /
• v.21 no.3
• /
• pp.11-16
• /
• 2003

다단 장약 터널 진동제어 발파에 대하여 개별요소법과 유한요소해석법으로 수치해석적으로 검증하였다. 그 결과, 단당 장약량을 줄이고 다단으로 분산시키면 발파로 인한 파쇄도 효과적이고, 진동도 감소할 수 있음을 보여 주었다. 이러한 현상에 대하여 파괴역학적으로도 설명하였다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.3
• /
• pp.459-467
• /
• 1992

본 연구에서는 비틀림 진동계에 있어서의 비틀림 진동현상을 억제하도록 제어 하기 위하여 최적제어 이론에 기초한 모델추종법을 비틀림 진동계에 적용하였다. 디 지탈 컴퓨터에 의한 제어를 위하여 제어 알고리즘은 디지탈 설계로 되어 있다. 제어 는 각속도와 비틀림 진동제어의 양면으로 수행되며, 축의 각속도는 모델의 출력을 추 종하게 되며 이와 동시에 비틀림각도 감소하게 된다.