• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.216-224
• /
• 2014

층간소음의 대부분의 원인이 아이들 뛰거나 발걸음으로 나타나고 있어 층간소음 저감을 위한 선행 연구로 층간소음의 주요 충격원인 보행 행위에 대한 정밀한 연구가 필요하다. 성인 보행 충격력과 그에 따른 바닥충격음을 계측하여 보행하중이 바닥충격음에 영향을 주는 요소를 분석하였다. 보행하중 중 발 뒤꿈치 충격력은 전체 충격하중을 주파수 특성을 대변할 수 있는 임펄스 형태의 하중으로 충격력은 뱅머신 또는 고무공보다 낮지만 1 차 영점(First zero)이 80Hz 정도로 높아 유효 가진 주파수 대역이 표준 중량충격원 보다 높았다. 구조물과 수음실의 고유모드 특성으로 인해 외부 충격에 대한 구조체 진동 및 음압의 공진 현상이 발생되기 때문에 공진 성분이 포함되는 바닥충격음 레벨은 순수 충격력 특성인 보행 또는 표준 중량충격원의 옥타브 밴드 충격력 폭로레벨과는 전혀 다른 주파수 특성을 나타내었다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.04a
• /
• pp.313-317
• /
• 1995

최근 환경오염이 심각한 사회문제로 대두됨에 따라 환경오염원을 제거하기 위한 여러 가지의 집진장치가 개발되고 있는데 화력발전소에서는 건식정전집진장치(dry electrostatic precipitator)를 이용하고 있다. 건식정전집진장치는 햄머(hammer) 방식의 충격장치를 설치하여 집진극과 방전극에 충격을 가함으로써 충격력을 극대화시키고 높은 분진박리 효과를 꾀하고 있는데 환경오염원이 되고 있는 집진판의 분진의 분리율을 높이기 위해서는 집진판의 전체 영역에서 분진을 동일하게 떨어뜨릴 수 있는 충격장치가 설계되어야 하는데, 이를 위해서는 충격하중에 따른 집진판의 진동 형태를 정확하게 분석하여야 한다. 본 연구에서는 집진판의 충격하중에 따른 진동의 형태를 분석하기 위해 펄스 레이저를 이용한 2중 노출 홀로그래피 시스템을 구성하였다. 홀로그래픽 간섭계는 이미 오래 전에 개발된 레이저 응용 계측기법으로서 주로 정현적인 진동을 하는 진동체의 진동 현상을 연구하는 데에 많이 사용되어 왔는데 그 기술 개발은 상당한 수준에 있다. 그러나 종래의 기술들은 주로 헬륨-네온(He-Ne)레이저와 같은 연속 레이저(continuous wave laser)를 이용한 기술들인데 최근에는 루비(ruby) 레이저와 같은 펄스 레이저 (pulse laser)를 이용한 기술이 많이 응용되고 있다. 이 펄스 레이저 홀로그래픽 간섭계를 Gottenberg는 응력파에 의해서 발생된 변형을 측정하기 위해 사용하였고 Aprahamian등은 보(beam)와 평판의 굽힘파(bending wave)의 전파 특성 연구에 이용하였다. 그 실험적 결과는 수치적 해석 결과와 비교되어 매우 좋은 일치성을 보였는데 이러한 펄스 레이져 홀로그래픽 간섭계 기법의 주요 장점은 어떠한 특정한 순간에 관찰하고자 하는 시험편의 전체 영역의 파동 전파 형상을 관찰할 수 있다는 것이다. 따라서 본 연구에서는 펄스 레이저를 응용한 2중 노출 홀로그래피법(double exposure holography method)을 이용해서 집진판에 충격하중이 가해졌을 때 발생하는 진동이 발생과 전파 특성을 충격하중의 방향에 따라서 분석하였다.

• Journal of the Korea Concrete Institute
• /
• v.16 no.2 s.80
• /
• pp.221-228
• /
• 2004

In recent years building floors become larger and more spacious due to the development of new design methods and high strength and light weight materials. However, such long span floor systems may provide smaller amount of damping and have a longer period so that they may be more vulnerable to the floor vertical vibration. In Korea when floors are to be checked against the floor vertical vibration, the provisions developed in foreign countries have been used. However these guidelines have been developed based on human perception, which may vary from country to country. Also, Korea have particular floor systems, such as flat plate floor system of apartment building. This study attempts to evaluate the vibration performance of the floors in typical apartment buildings. Two different floors with the area of $28 m^2$ and $32 m^2$ were investigated. The criteria provided by ATC-1(1999), AISC-11(1997), AIJ(1991) and the local criteria developed in the previous study(Han, 2003) was used to check the acceptability of the floor vertical vibration.

• Tunnel and Underground Space
• /
• v.29 no.3
• /
• pp.135-147
• /
• 2019

This paper introduced a impact load estimation method by examining vibration transfer path analysis (TPA). The theoretical background and the load quantification procedure are explained, and a case study of hydraulic breaker is reported. We explained the merits and limitations of the load estimation method of TPA, and improvement method was suggested through case analyses of drilling equipment. The necessity of R&D of load-estimation technology was discussed. A new strategy for developing new techniques for impact load measurement was proposed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.244-249
• /
• 2011

The potential hazards resulting from a low-velocity impact (bird-strike, tool drop, runway debris, etc.) on aircraft structures, such as engine nacelle or a leading edges, has been a long-term concern to the aircraft industry. Certification authorities require that exposed aircraft components must be tested to prove their capability to withstand low-velocity impact without suffering critical damage. In most of the past research studies unloaded specimens have been used for impact tests, however, in reality it is much more likely that a composite structure is exposed to a certain stress state when it is being impacted, which can have a significant effect on the impact performance. And the radiated impact sound induced by impact is analyzed for the damage detection evaluation. In this study, an investigation was undertaken to evaluate the effect in-plane loading on the impact force and sound of composite laminates numerically.

• The Journal of the Acoustical Society of Korea
• /
• v.26 no.6
• /
• pp.235-242
• /
• 2007

The test and evaluation of floor impact sound is mainly conducted before move in the residence. Floor impact sound generating is actually the conditions in which a heavy load like a curtain and furniture is installed, the situation before and after move in the residence is different. In this study, we investigate the floor impact sound variations according to the live load installation like furniture in the source room. The vibration acceleration level and floor impact sound level variation were measured before and after live load ($200kg/m^2$) installation in the floor impact sound test building and the field. The difference was not large although the vibration acceleration level and the floor impact sound level were reduced through measurement result of load installation. Resonance frequency was not changed by load installation.

• Journal of the Korean Institute of Gas
• /
• v.13 no.1
• /
• pp.1-8
• /
• 2009

Recently, the vibration of underground structure due to high speed railway loads has been increased substantially as compared with middle and slow speed. The buried gas pipelines under continuous impact forces and repeated loading are more influenced by the vibrational loads than another pipelines. However, the static analysis was not enough to allow for the effect of vibrations because it uses impact factors for the design or analysis process. In this study, characteristics of Pipelines was quantitatively estimated through each conditions of soil covers and train speed, and the new vibration prediction is presented about the vibrational velocity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.04a
• /
• pp.633-637
• /
• 2011

The tall and slender main crane is generally installed on the upper deck to load and unload the equipment or something heavy in the drilling rig or the ship. So the natural frequency of the crane equipment is very low, therefore, there is some possibility of excessive vibration at the emergency state due to sudden stop during the crane operation. This study describes a fatigue assessment due to heavy vibration during brake test of sudden stop because it is necessary the safety of crane is estimated against the heavy vibration. In order to find out the applied force, the vibration measurement and analysis have been performed.

• Explosives and Blasting
• /
• v.38 no.1
• /
• pp.23-29
• /
• 2020

The measurement technique with dynamic shock sensor was widely used in academic experiment for blasting and impact. However, most of dynamic sensors are expensive so that it needs to be protected by external housing structures or damping devices. In this study, the calibration method for dynamic shock sensor under the distortion by external structures. Hopkinson pressure bar system was adopted to measure the input acceleration to the sensor, and it was compared to the acceleration measured by accelerometer with customized damping device. Consequently, it is conclued that this method can be useful to calibrate the dynamic shock sensor under the linear distortion.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.17 no.2
• /
• pp.167-181
• /
• 2019

Currently, the development of evaluation technology for vibration and shock load characteristics and spent nuclear fuel structural integrity under normal conditions of transport is being conducted in the Republic of Korea. This is the first such research conducted in the Republic of Korea and, thus, previous international studies need to be investigated and will be referred to in the ongoing project. Before 2000, several studies related to measurement of vibration and shock loads on spent nuclear fuel were conducted in the US. US national research institutes conducted uniaxial fuel assembly shaker tests, concrete block tests, and multi-axis fuel assembly tests between 2009 and 2016. In 2017, multi-modal transportation tests including road, sea, and rail transport were also performed by research institutes from the US, Spain and the Republic of Korea. Therefore, test preparation procedures, acceleration and strain measurement results, and finite-element and multi-body dynamics analysis were investigated. Based on the measured strain data, the preliminary conclusion was obtained that the measured strain was too small to cause damage to spent nuclear fuel rods. However, this conclusion is a preliminary conclusion that only reviews part of the results; a detailed review is being conducted in the US. The investigation of international studies on spent nuclear fuel structural integrity tests considering vibration and shock loads under normal conditions of transport in the US will be useful data for the project being conducted in the Republic of Korea.