• 한국공간정보시스템학회:학술대회논문집
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• 한국공간정보시스템학회 2004년도 춘계 학술발표회 논문집 제1권1호(통권1호)
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• pp.161-168
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• 2004

The dynamic instability of snapping phenomena has been studied by many researchers. Few papers deal with dynamic buckling under loads with periodic characteristics, and the behavior under periodic excitations is expected to be different from behavior under STEP excitations. We investigate the fundamental mechanisms of the dynamic instability when the sinusoidally shaped arch structures are subjected to sinusoidally distributed excitations with pin-ends. The mechanisms of dynamic indirect snapping of shallow arches are especially investigated under not only STEP function excitations but also under sinusoidal harmonic excitations, applied in the up-and-down direction. The dynamic nonlinear responses are obtained by the numerical integration of the geometrically nonlinear equation of motion, and examined by Fourier spectral analysis in order to get the frequency-dependent characteristics of the dynamic instability for various load levels.

• Smart Structures and Systems
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• 제21권3호
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• pp.335-347
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• 2018

The fast-growing number of mobile and wearable applications has driven several innovations in small-scale electret-based energy harvesting due to the compatibility with standard microfabrication processes and the ability to generate electrical energy from ambient vibrations. However, the current modeling methods used to design these small scale transducers or microgenerators are applicable only for constant-speed rotations and small sinusoidal translations, while in practice, large amplitude sinusoidal vibrations can happen. Therefore, in this paper, we formulate an analytical model for electret-based microgenerators under general sinusoidal excitations. The proposed model is validated using finite element modeling combined with numerical simulation approaches presented in the literature. The new model demonstrates a good agreement in estimating both the output voltage and power of the microgenerator. This new model provides useful insights into the microgenerator operating mechanism and design trade-offs, and therefore, can be utilized in the design and performance optimization of these small structures.

• 한국공간구조학회논문집
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• 제4권2호
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• pp.81-88
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• 2004

동적 불안정 좌굴현상에 관한 연구는 다소 발표되고 있으나, 주기성을 가진 하중하에서의 동적 좌굴을 다룬 연구는 그리 많지 않은 편이다. 주기성을 가진 하중하에서의 거동은 STEP 하중하에서의 거동과는 매우 다르리라 예상된다. 본 논문에서는 동적 불안정의 기본 메커니즘을 파악하기 위하여 양단 핀으로 고정된 정현형 아치가 정현형 조화하중을 받았을 때의 얕은 아치를 대상으로 한다. 얕은 아치의 동적 간접 좌굴 메커니즘을 파악하기 위하여 STEP 하중뿐만 아니라 정현형 조화하중일 때를 대상으로 한다. 동적 비선형 응답 특성을 알기 위하여 수치적분에 의해 기하학적 비선형 운동방정식을 유도한다. 여기서 얻어진 비선형 변위 응답으로 FFT(Fast Fourier Transform)에 의한 연속 응답 스펙트럼을 구해 동적 불안정 특성에 관해서 분석한다.

• 한국공간구조학회논문집
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• 제14권1호
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• pp.85-91
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• 2014

The purpose of this paper is to study comparative of dynamic instability characteristic of Geiger-typed cable dome structures by load condition, which is well-known among the cable dome structures that are the lightweight hybrid structure using compression and tension element continuously. Dynamic buckling process in the phase plane is very important thing for understanding why unstable phenomena are sensitively originated in nonlinear dynamic by various initial conditions. But there is no paper for the dynamic instability of hybrid cable dome by Sinusoidal Excitations, many papers which deal with the dynamic instability for shell-structures under the step load have been published. As a result of Geiger-typed cable dome, which shows chaotic behavior in dynamic nonlinear analysis with initial imperfection.

• Smart Structures and Systems
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• 제19권2호
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• pp.181-194
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• 2017

In order to investigate the interface debonding defects detection mechanism between steel tube and concrete core of concrete-filled steel tubes (CFSTs), multi-physical fields coupling finite element models constituted of a surface mounted Piezoceramic Lead Zirconate Titanate (PZT) actuator, an embedded PZT sensor and a circular cross section of CFST column are established. The stress wave initiation and propagation induced by the PZT actuator under sinusoidal and sweep frequency excitations are simulated with a two dimensional (2D) plain strain analysis and the difference of stress wave fields close to the interface debonding defect and within the cross section of the CFST members without and with debonding defects are compared in time domain. The linearity and stability of the embedded PZT response under sinusoidal signals with different frequencies and amplitudes are validated. The relationship between the amplitudes of stress wave and the measurement distances in a healthy CFST cross section is also studied. Meanwhile, the responses of PZT sensor under both sinusoidal and sweep frequency excitations are compared and the influence of debonding defect depth and length on the output voltage is also illustrated. The results show the output voltage signal amplitude and head wave arriving time are affected significantly by debonding defects. Moreover, the measurement of PZT sensor is sensitive to the initiation of interface debonding defects. Furthermore, wavelet packet analysis on the voltage signal under sweep frequency excitations is carried out and a normalized wavelet packet energy index (NWPEI) is defined to identify the interfacial debonding. The value of NWPEI attenuates with the increase in the dimension of debonding defects. The results help understand the debonding defects detection mechanism for circular CFST members with PZT technique.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.492-497
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• 2003

The dynamic instability for snapping phenomena has been studied by many researches. There is few paper which deal with the dynamic buckling under the load with periodic characteristics, and the behavior under periodic excitation is expected the different behavior against STEP excitation. We investigate the fundamental mechanisms of the dynamic instability when the sinusoidal shaped arch structures subjected to sinusoidal distributed excitation with pin-ends. In this study, the dynamic direct snapping of shallow arches is investigated under not only STEP load excitation but also sinusoidal harmonic excitations, applied in the up-and-down direction. The dynamic nonlinear responses are obtained by the numerical integration of the geometrically nonlinear equations of motion, and examined by the Fourier spectral analysis in order to get the frequency-dependent characteristics of the dynamic instability for various load levels.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 추계학술발표회요약집
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• pp.141.1-141
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• 2002

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.687-692
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• 2002

In order to verify the effectiveness of adding visooelastic dampers to full-scale steel frame structure on the reduction of their seismic and wind response a experimental work was carried out. First, The test was conducted on the VE dampers subjected to sinusoidal excitations under a variety of ambient temperatures, frequency, and the damper strain. Results from these tests showed that the viscoelastic dampers have high energy dissipation capacity. Second, The vibration tests was conducted of the full-scale steel frame structure with md without added VE dampers at different temperatures. Viscoelastically damped full-scale structure test result on the effect of ambient temperature show that viscoelastic dampers are very effective in reducing excessive vibration of the structure due to sinusoidal excitation over a wide ringe of ambient temperature.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.369.1-369
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• 2002

In order to verify the effectiveness of adding viscoelastic dampers to full-scale steel frame structure on the reduction of their seismic and wind response, a experimental work was carried out. First, The test was conducted on the VE dampers subjected to sinusoidal excitations under a variety of ambient temperatures, frequency, and the damper strain. Results from these tests showed that the viscoelastic dampers have high energy dissipation capacity Second, (omitted)

• Structural Engineering and Mechanics
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• 제29권3호
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• pp.241-258
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• 2008

This paper presents a new identification approach to prestress force. Firstly, a bridge deck is modeled as a prestressed Timoshenko beam. The time domain responses of the beam under sinusoidal excitation are studied based on modal superposition. The prestress force is then identified in the time domain by a system identification approach incorporating with the regularization of the solution. The orthogonal polynomial function is used to improve the noise effect and obtain the derivatives of modal responses of the bridge. Good identification results are obtained from only the first few measured modal data under both sinusoidal and impulsive excitations. It is shown that the proposed method is insensitive to the magnitude of force to be identified and can be successfully applied to indirectly identify the prestress force as well as other physical parameters, such as the flexural rigidity and shearing rigidity of a beam even under noisy environment.