• Smart Structures and Systems
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• 제7권2호
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• pp.83-102
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• 2011

As a testbed for various structural health monitoring (SHM) technologies, a super-tall structure - the 610 m-tall Guangzhou Television and Sightseeing Tower (GTST) in southern China - is currently under construction. This study aims to explore state-of-the-art wireless sensing technologies for monitoring the ambient vibration of such a super-tall structure during construction. The very nature of wireless sensing frees the system from the need for extensive cabling and renders the system suitable for use on construction sites where conditions continuously change. On the other hand, unique technical hurdles exist when deploying wireless sensors in real-life structural monitoring applications. For example, the low-frequency and low-amplitude ambient vibration of the GTST poses significant challenges to sensor signal conditioning and digitization. Reliable wireless transmission over long distances is another technical challenge when utilized in such a super-tall structure. In this study, wireless sensing measurements are conducted at multiple heights of the GTST tower. Data transmission between a wireless sensing device installed at the upper levels of the tower and a base station located at the ground level (a distance that exceeds 443 m) is implemented. To verify the quality of the wireless measurements, the wireless data is compared with data collected by a conventional cable-based monitoring system. This preliminary study demonstrates that wireless sensing technologies have the capability of monitoring the low-amplitude and low-frequency ambient vibration of a super-tall and slender structure like the GTST.

• 대한토목학회논문집
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• 제42권1호
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• pp.23-33
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• 2022

상시미동의 수직성분에 대한 수평성분 스펙트럼비(HVSR)는 부지 공명주파수를 파악하는데 활발히 사용되고 있다. HVSR의 가장 큰 비율을 가지는 주파수는 부지 공명주파수와 일치한다. 상시미동은 부지 주변에 존재하는 미세진동을 의미하기 때문에 직접적인 진동원을 파악할 수 없으며, 또한 조절할 수 없다. 따라서 신뢰적인 상시미동 HVSR을 구하기 위해서는 상시미동 측정에 충분한 시간적 여유와 주변 환경의 파악 또한 필요하다. 본 연구에서는 신뢰적인 HVSR 분석에 필요한 상시미동 측정 최소시간과 지진계와 인위적인 진동 사이의 이격거리의 영향을 알아보았다. 토사 부지의 경우 센서 설치 후 5분 이내에 안정화가 되었으나, 암반 부지의 경우 안정화까지 1시간 이상이 소요되었다. 또한 상시미동 관측 시 발걸음 진동이 지진계 10 m 이내에 존재할 경우 HVSR결과에 큰 영향을 미치는 것을 확인하였다. 이러한 결과는 현장에서 상시미동의 HVSR측정에 필요한 가이드라인을 제공할 것으로 기대된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.535-542
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• 2010

Various difficulties have been increased in the construction of public structure; like the road in the overcrowding urban area, because of civil complaint, cost and period of construction. In oder to overcome these social problems, the tunnel has been planned the road design. Despite the resolution, there are many technical problems when constructed near facilities. The design of new tunnel below the existing service reservoir is applied to the ambient vibration blasting using Plasma. The result of test blasting was exceeded the standard ("2kine"). So it was considered a countermeasure for the vibration reduction applied to change the controlled blasting method, reduce the charge, add the pre middle horizontal hole in the cut blasting site, and so on. The result was satisfied the standard. Accordingly, if the quality of blasting process can be managed well, the application of this alternative method is highly effective one. Also, based on cost analysis between two methods, the alternative method is very competitive.

• 터널과지하공간
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• 제20권4호
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• pp.252-259
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• 2010

도심지 터널 즉 터널의 상부 근접한 거리에 보안물건이 존재하는 경우 일반적인 폭약만을 사용해서는 발파진동을 규제치내에서 조절이 불가능하여 폭약공법이 아닌 무진동, 미진동 공법을 사용해야 한다. 하지만 무진동 공법들은 터널굴착공사비가 크게 증가 하게 되며, 또 공사기간도 길어진다. 일반적으로 노천채굴에서는 폭속이 약2,000 m/s 정도인 저폭속폭약이 응용 사용되어 왔으나 터널발파에는 사용되지 않았다. 본 연구에서는 저폭속폭약을 일반 폭약과 공내에서 혼용장약하여 발파작업을 한 결과 일반 폭약으로 발파하는 것보다 진동이 25~30%정도가 감소하였다. 도심지터널 및 보안물건 근접한 터널에서는 진동규제치내에서 미진동으로 시공할 수 있는 저폭속폭약과 일반폭약을 혼용 사용하는 발파 방법을 사용하는 것이 효과적인 것으로 나타났다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.131-137
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• 1996

To perform condition monitoring of P.C. Box girder bridge under ambient traffic, dynamic characteristics were identified using the results of load test an analysis. It was found that natural frequencies obtained from the measured acceleration data for the forced vibration part and free vibration part were nearly identical. Thus it can be concluded that dynamic parameters are properly determined under ambient traffic condition. Finite element model for analysis was calibrated using measured frequencies. Change of dynamic characteristics were predicted through analysis of the established finite element model with anticipated change.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.385.1-385
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• 2002

Operational Modal Analysis also known as Ambient Modal Analysis has an increasing interest in mechanical cngineering. Especially on big structures where the excitation and not less important the determination of the forces is most often a problem. In a structure like a wind turbine wing where the modes occur both close in frequency and bi-directional the Ambient excitation has big advantages. (omitted)

• Smart Structures and Systems
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• 제25권4호
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• pp.487-499
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• 2020

This paper proposes a novel approach to model updating for a large-scale cable-stayed bridge based on ambient vibration tests coupled with a hybrid metaheuristic search algorithm. Vibration measurements are carried out under excitation sources of passing vehicles and wind. Based on the measured structural dynamic characteristics, a finite element (FE) model is updated. For long-span bridges, ambient vibration test (AVT) is the most effective vibration testing technique because ambient excitation is freely available, whereas a forced vibration test (FVT) requires considerable efforts to install actuators such as shakers to produce measurable responses. Particle swarm optimization (PSO) is a famous metaheuristic algorithm applied successfully in numerous fields over the last decades. However, PSO has big drawbacks that may decrease its efficiency in tackling the optimization problems. A possible drawback of PSO is premature convergence leading to low convergence level, particularly in complicated multi-peak search issues. On the other hand, PSO not only depends crucially on the quality of initial populations, but also it is impossible to improve the quality of new generations. If the positions of initial particles are far from the global best, it may be difficult to seek the best solution. To overcome the drawbacks of PSO, we propose a hybrid algorithm combining GA with an improved PSO (HGAIPSO). Two striking characteristics of HGAIPSO are briefly described as follows: (1) because of possessing crossover and mutation operators, GA is applied to generate the initial elite populations and (2) those populations are then employed to seek the best solution based on the global search capacity of IPSO that can tackle the problem of premature convergence of PSO. The results show that HGAIPSO not only identifies uncertain parameters of the considered bridge accurately, but also outperforms than PSO, improved PSO (IPSO), and a combination of GA and PSO (HGAPSO) in terms of convergence level and accuracy.

• 한국소음진동공학회논문집
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• 제11권5호
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• pp.108-122
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• 2001

As bridge design is advancing toward the performance-based design. it becomes increasingly important to monitor and re-evaluate the long-term structural performance of bridges. Such information is essential in developing performance criteria for design. In this research. sensor systems for long-term structural performance monitoring have been installed on two highway bridges. Pre1iminary vibration measurement and data analysis have been performed on these instrumented bridges. On one bridge, ambient vibration data have been collected. based on which natural frequencies and mode shapes have been extracted using various methods and compared with those obtained by the preliminary finite element analysis. On the other bridge, braking and bumping vibration tests have been carried out using a water truck In addition to ambient vibration tests. Natural frequencies and mode shapes have been derived and the results by the breaking and bumping vibration tests have been compared. For the development of a three dimensional baseline finite element model, the new methodology using a neural network is proposed. The proposed one have been verified and applied to develop the baseline model of the bridge.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.277-277
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• 2009

In this paper, PMPG (Piezoelectric Micro Power Generator) was investigated by ANSYS FEA (Finite Element Analysis) to decrease operating frequency and improve out power. The micro power generator was designed to convert ambient vibration energy to electrical power as a ZnO piezoelectric material. To find optimal model in low vibration ambient, the shape of power generator was changed with different membrane width, thickness, length, and proof mass size. Used the ANSYS modal analysis, bending mode and stress distribution of optimal model were analyzed. Also, the displacement with the frequency range was analyzed by harmonic analysis. From the simulation results, the resonance frequency of optimal model is about 373 Hz and confirmed the possibility of ZnO micro power generator for wireless sensor node applications.

• 대한기계학회논문집A
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• 제28권6호
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• pp.717-725
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• 2004

A power generation systems are proposed to convert ambient mechanical vibration into electrical energy using cantilever-type piezoelectric materials. The vibration-based power device can be used for self-powered systems without batteries. This paper presents the theoretical analysis for the coupled equations of piezoelectric and structural motions and investigates the dynamic characteristics of the self-power system using transfer function method. The theoretical model is verified by the finite element analysis of the resonance frequency, the dynamic response of the structure and the sensor sensibility. Experimental results measured using a prototype system agree with the theoretical predictions. The system is shown to produce 34.5 ㎼ in average. Finally, we perform the optimal design for system variables to maximize output power.