표준 중량 충격원과 실충격원에 대한 공동주택의 바닥진동 및 바닥충격음 음압레벨 특성

이민정(Lee, Min-Jung),최현기(Choi, Hyun-Ki) 대한건축학회 2017 大韓建築學會論文集 : 構造系 Vol.33 No.6

To evaluate the floor impact sound insulation performance bang machine is used as standard heavyweight impact source. Impact ball was known as more suitable impact source to represent the dynamic force induced by jumping or running of child and adopted as heavyweight impact source in evaluation criterion for a while. However, performance level of floor impact sound insulation depended on selection of heavyweight impact source, which caused controversy about the suitability of standard heavyweight impact sources. So bang machine became the only standard heavyweight impact source again. Floor impact sound is structure-borne sound, thus the characteristic of standard impact source needs to be determined in the light of floor impact sound pressure level along with the dynamic responses of slab and bearing walls for floor vibration. The purpose of this study was to investigate the characteristics of floor vibration and floor impact sound pressure level according to impact sources. For the purpose vibration test was conducted using bang machine, impact ball, and jumping and running activities of four-year-old child as impact sources. From the results vibration modes of slab and walls for floor vibration and the acceleration ratios of transmitted vibration from slab to wall were investigated. And this study also inquired into floor impact sound pressure levels and the influence of characteristics of slab and walls for floor vibration according to impact sources.

진동절연재로 보강된 기둥부재의 진동저감효과 및 구조적 거동분석

김진호,이나현,허진호,김희규 한국구조물진단유지관리공학회 2016 한국구조물진단유지관리공학회 논문집 Vol.20 No.4

For elevated railway station on which track is connected with superstructure of station, structural vibration level and structure-borne-noise level has exceeded the reference level due to structural characteristics which transmits vibration directly. Therefore, existing elevated railway station is in need of economical and effective vibration reduction method which enable train service without interruption. In this study, structural vibration non-transmissible system which is applied to vibroisolating material for column member is developed to reduce vibration. That system is cut covering material of the column section using water-jet method and is installed with vibroisolating material on cut section. To verify vibration reduction effect and structural performance for structural vibration non-transmissible system, impact hammer test and cyclic lateral load test are performed for 1/4 scale test specimens. It is observed that natural period which means vibration response characteristics is shifted , and damping ratio is increased about 15~30% which means that system is effective to reduce structural vibration through vibration test. Also load-displacement relation and stiffness change rate of the columns are examined, and it is shown that ductility and energy dissipation capacity is increased. From test results, it is found that vibration non-transmissible system which is applied to column member enable to maintains structural function. 궤도가 역사의 상부에 위치하여 열차운행으로 인하여 발생한 진동이 직접 전달되는 선하역사에서 구조물 진동과 이로 인한 구조물 기인 소음이 기준치보다 높은 것으로 나타남에 따라, 기존 선하역사에 대하여 열차 운행의 중단 없이 진동저감이 가능한 경제적, 효율적 방안이 요구된다. 이에 본 연구에서는 진동전달 경로상의 기둥에 워터젯 공법으로 기둥단면에서 피복재 부분을 파쇄한 후 진동전달 절연기능을 가지는 에폭시 소재의 방진재를 보강하여 진동을 저감시키기 위한 구조진동절연시스템을 개발하였다. 방진재의 보강체적을 변수로 한 진동절연시스템을 실제역사 기둥의 1/4축소모형에 적용하고, 충격가진 시험을 통한 진동저감 성능과 횡하중 반복가력시험을 통한 구조적 성능을 검증하고자 하였다. 충격가진 실험결과로부터 구조진동절연시스템을 적용할 경우 고유 진동주기가 하향되어 진동응답 특성이 변화되고 감쇠비는 약 15~ 30%까지 증가를 나타내어 진동저감 성능이 있음을 알 수 있었다. 또한 반복하중 가력에 의한 구조성능 실험에서 하중-변위 및 강성변화에 대한 고찰과 연성도 및 에너지 소산의 증가를 보인 결과로 부터 구조부재로의 기능을 유지함을 확인 할 수 있었다.

Impact Echo Test for the Dynamic Characteristics of a Vibration-Mitigated Concrete Structure

Chung, Young-Soo,Park, Young-Goo Korea Concrete Institute 2002 KCI concrete journal Vol.14 No.1

Recent construction activities have given rise to civil petitions associated with vibration-induced damages or nuisances. To mitigate unfavorable effects of construction activities, the measures to reduce or isolate from vibration need to be adopted. In this research, a vibration-mitigated concrete, which is one of the active measures for reducing vibration in concrete structures, was investigated. Concrete was mixed with vibration-reducing materials (i.e. latex, rubber power, plastic resin, and polystyrofoam) to reduce vibration and tested to evaluate dynamic material properties and structural characteristics. Normal and high strength concrete specimens with a certain level of damage were also tested for comparisons. In addition, recycling tires and plastic materials were added to produce a vibration-reducing concrete. A total of 32 concrete bars and eight concrete beams were tested to investigate the dynamic material properties and structural characteristics. Wave measurements on concrete bars showed that vibration-mitigated concrete has larger material damping ratio than normal or high strength concrete. Styrofoam turned out to be the most effective vibration-reducing mixture. Flexural vibration tests on eight flexural concrete beams also revealed that material damping ratio of the concrete beams is much smaller than structural damping ratio for all the cases.

Vibration and impact monitoring of a composite-wing model using piezoelectric paint

The Korean Society for Composite Materials 2014 Advanced composite materials Vol.23 No.1

This study investigates a piezoelectric paint sensor for large area sensing applications, and its sensing characteristics under dynamic loading conditions such as impact and vibration. The piezoelectiric paint is composed of the <TEX>$Pb(Nb,Ni)O_3-Pb(Zr,Ti)O_3$</TEX> (PNN-PZT) powder and epoxy resin. The PNN-PZT is a kind of soft piezoelectric material that offers many advantages such as high piezoelectric properties, easy poling, and so on. The PNN-PZT/epoxy paint sensor can be easily applied to various engineering structures, even to those having a complex geometry or curved shapes because of its flexibility. In this study, the PNN-PZT/epoxy paint was coated on a composite-wing model. One electrode was made on the upper surface of the piezoelectric paint, while the graphite/epoxy composite structure itself was used as the other electrode. Then poling was conducted at room temperature (<TEX>$20^{\circ}C$</TEX>) under a 4 kV/mm electric field for 10 min. When the composite-wing model was subjected to tree-vibration, its vibration response was monitored by measuring the output voltage of the piezoelectric paint sensor; when the composite-wing model was impacted by an impact hammer, its impact signal was also measured by the piezoelectric paint sensor. The vibration and impact test results showed that the PNN-PZT/epoxy paint sensor captured the dynamic responses of the composite-wing structure very well. We believe that the piezoelectric paint sensor can be useful in many engineering applications such as real-time vibration and impact monitoring, damage detection, nondestructive structural health monitoring, and so on.

거주자의 거동으로 발생하는 바닥진동의 층간 전달 및 바닥충격음의 음압레벨 특성 평가

이민정(Min Jung Lee),최현기(Hyun Ki Choi) 한국소음진동공학회 2017 한국소음진동공학회 논문집 Vol.27 No.1

Noise complaints among neighbors in apartment building are mainly caused by floor impact noise that is structure born noise due to occupant induced floor vibration. To control this noise problems many researchers have investigated floor systems and finishing materials. Light-weight impact noise affects by finishing materials, but heavy-weight impact noise induced by heel impacts during normal walking or jumping of children is concerned with structural system and floor vibration. To figure out the characteristics of floor impact noise and transmission of floor vibration due to human activities, vibration tests were conducted in apartment buildings. Impact hammer, heel drop and walking activities were loaded at center of upstairs living room, and accelerations of slabs for both upstairs and downstairs and sound pressure levels for downstairs were measured. The acceleration ratio of transmitted floor vibration to downstairs and human induced vibration in upstairs was between 0.5 and 1.0 according to slab size, wall, and load type. And floor impact noise occurred in the range of natural frequency of slab.

진동절연재로 보강된 기둥부재의 진동저감효과 및 구조적 거동분석

김진호,이나현,허진호,김희규 한국구조물진단유지관리공학회 2016 한국구조물진단유지관리공학회 논문집 Vol.20 No.4

For elevated railway station on which track is connected with superstructure of station, structural vibration level and structure-borne-noise level has exceeded the reference level due to structural characteristics which transmits vibration directly. Therefore, existing elevated railway station is in need of economical and effective vibration reduction method which enable train service without interruption. In this study, structural vibration non-transmissible system which is applied to vibroisolating material for column member is developed to reduce vibration. That system is cut covering material of the column section using water-jet method and is installed with vibroisolating material on cut section. To verify vibration reduction effect and structural performance for structural vibration non-transmissible system, impact hammer test and cyclic lateral load test are performed for 1/4 scale test specimens. It is observed that natural period which means vibration response characteristics is shifted , and damping ratio is increased about 15~30% which means that system is effective to reduce structural vibration through vibration test. Also load-displacement relation and stiffness change rate of the columns are examined, and it is shown that ductility and energy dissipation capacity is increased. From test results, it is found that vibration non-transmissible system which is applied to column member enable to maintains structural function.

Dynamics of an elastic beam and a jumping oscillator moving in the longitudinal direction of the beam

Baeza, Luis,Ouyang, Huajiang Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.3

An oscillator of two lumped masses linked through a vertical spring moves forward in the horizontal direction, initially at a certain height, over a horizontal Euler beam and descends on it due to its own weight. Vibration of the beam and the oscillator is excited at the onset of the ensuing impact. The impact produced by the descending oscillator is assumed to be either perfectly elastic or perfectly plastic. If the impact is perfectly elastic, the oscillator bounces off and hits the beam a number of times as it moves forward in the longitudinal direction of the beam, exchanging its dynamics with that of the beam. If the impact is perfectly plastic, the oscillator (initially) sticks to the beam after its first impact and then may separate and reattach to the beam as it moves along the beam. Further events of separation and reattachment may follow. This interesting and seemingly simple dynamic problem actually displays rather complicated dynamic behaviour and has never been studied in the past. It is found through simulated numerical examples that multiple events of separation and impact can take place for both perfectly elastic impact and perfectly plastic impact (though more of these in the case of perfectly elastic impact) and the dynamic response of the oscillator and the beam looks noisy when there is an event of impact because impact excites higher-frequency components. For the perfectly plastic impact, the oscillator can experience multiple events of consecutive separation from the beam and subsequent reattachment to it.

Dynamics of an elastic beam and a jumping oscillator moving in the longitudinal direction of the beam

Luis Baeza,Huajiang Ouyang 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.3

An oscillator of two lumped masses linked through a vertical spring moves forward in the horizontal direction, initially at a certain height, over a horizontal Euler beam and descends on it due to its own weight. Vibration of the beam and the oscillator is excited at the onset of the ensuing impact. The impact produced by the descending oscillator is assumed to be either perfectly elastic or perfectly plastic. If the impact is perfectly elastic, the oscillator bounces off and hits the beam a number of times as it moves forward in the longitudinal direction of the beam, exchanging its dynamics with that of the beam. If the impact is perfectly plastic, the oscillator (initially) sticks to the beam after its first impact and then may separate and reattach to the beam as it moves along the beam. Further events of separation and reattachment may follow. This interesting and seemingly simple dynamic problem actually displays rather complicated dynamic behaviour and has never been studied in the past. It is found through simulated numerical examples that multiple events of separation and impact can take place for both perfectly elastic impact and perfectly plastic impact (though more of these in the case of perfectly elastic impact) and the dynamic response of the oscillator and the beam looks noisy when there is an event of impact because impact excites higher-frequency components. For the perfectly plastic impact, the oscillator can experience multiple events of consecutive separation from the beam and subsequent reattachment to it.

Impact noise radiated by collision of two spheres: Comparison between numerical simulations, experiments and analytical results

K. Mehraby,H. Khademhosseini Beheshti,M. Poursina 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.7

Impact is very common source of noise in the industries. The impacts can be visible, such as forging, and can be invisible, such as impacts due to clearance of hinges. As a result of this generality, the control of impact noise needs more attention. Reduction of this tiresome noise needs enough perception about the impact. A study of this noise sources presents difficult problems both theoretically and experimentally. This is partly due to the many complex interconnected mechanical phenomena that occur and partly due to the fact that usual steady-state techniques of analysis cannot be applied. In such complex problems numerical techniques can help to acousticians. To gain some insight into this source of sound, in this paper collision of two steel spheres are studied with finite element method (FEM). Then the FEM results were compared with experiments to show authority of this numerical method to simulate impact noises. FEM results show that if the vibrational modes are excited by impact, the vibrational modes can be as effective as rigid body motion.

Design and experimental analysis of new industrial vibration dampers

Mohamed Gharib,Mansour Karkoub 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.8

Vibration dampers are the first line of defense against shock and impacts sustained by mechanical and structural systems. Consequently, for decades, new impact damping technologies have been developed and applied in several engineering fields to attenuate undesired vibrations. Linear particle chain (LPC) impact dampers are the latest category of impact dampers being developed for the mitigation of unwanted vibrations in many systems. However, the challenges associated with prototyping such devices made their application in practical systems very limited. This paper proposes five innovative designs for the LPC impact dampers satisfying a wide range of industry needs in terms of efficiency, cost, and sustainability. The proposed designs are fabricated and tested under the same conditions to assess their efficiency in attenuating the vibration of a simple structure. Each design showed consistent behavior, but some designs outperformed others depending on the geometry, physical characteristics, and type of structure. The detailed design, experimental study, and time response comparisons are presented here to provide an initial study towards the development of practical sustainable LPC vibration dampers for real engineering applications.