• Smart Structures and Systems
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• 제20권2호
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• pp.231-246
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• 2017

A recent work by the authors has demonstrated the feasibility of scour evaluation for Kao-Ping-Hsi Cable-Stayed Bridge simply based on ambient vibration measurements. To further attain the goal of scour monitoring, a key challenge comes from the interference of several environmental factors that may also significantly alter the pier frequencies without the change of scour depth. Consequently, this study attempts to investigate the variation in certain modal frequencies of this bridge induced by several environmental factors. Four sets of pier vibration measurements were taken either during the season of plum rains, under regular summer days without rain, or in a period of typhoon. These signals are analyzed with the stochastic subspace identification and empirical mode decomposition techniques. The variations of the identified modal frequencies are then compared with those of the corresponding traffic load, air temperature, and water level. Comparison of the analyzed results elucidates that both the traffic load and the environmental temperature are negatively correlated with the bridge frequencies. However, the traffic load is clearly a more dominant factor to alternate the identified bridge deck frequency than the environmental temperature. The pier modes are also influenced by the passing traffic on the bridge deck, even though with a weaker correlation. In addition, the variation of air temperature follows a similar tendency as that of the passing traffic, but its effect on changing the bridge frequencies is obviously not as significant. As for the effect from the alternation of water level, it is observed that the frequency baselines of the pier modes may positively correlate with the water level during the seasons of plum rains and typhoon.

• 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.

• 환경영향평가
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• 제10권4호
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• pp.305-317
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• 2001

Effects on increased noise influenced residents on the urban areas as well as the rural areas because of rapidly increasing traffic volume and newly-constructed road. The object of this study is to better establish environmental policy for the year 2000s through analyzing current environment administration system in the field of noise and vibration. Noise and vibration administration system in Korea is composed of various standards in areas of noise environment, traffic noise regulation, living noise regulation, factory noise and vibration regulation, and aircraft noise regulation. Furthermore, there exists environment noise and vibration monitoring networking system. This study is to improve noise and vibration administration system through analyzing present condition and problems. This study suggests improved noise and vibration administration system by achieving four steps ; 1) goal establishment in noise and vibration administration system; 2) development of reduction mitigation method; 3) estimation of reduction mitigation method; 4) establishment of enforcement method. Proposed "Noise and Vibration Policy Committee" should be established to harmonize noise and vibration policy on scientific basis for the $21^{st}$ century.

• Smart Structures and Systems
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• 제17권3호
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• pp.491-522
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• 2016

A benchmark problem for modal identification of a cable-stayed bridge was proposed by a research team at Hong Kong Polytechnic University. By taking an instrumented cable-stayed bridge as a test bed, nineteen sets of vibration records with known/unknown excitations were provided to invited researchers. In this paper, the vibration responses of the bridge under a series of excitation conditions are examined to estimate the wind and traffic-induced variations of its dynamic characteristics. Firstly, two output-only experimental modal identification methods are selected. Secondly, the bridge and its monitoring system are described and the nineteen sets of vibration records are analyzed in time-domain and frequency-domain. Excitations sources of blind datasets are predicted based on the analysis of excitation conditions of known datasets. Thirdly, modal parameters are extracted by using the two selected output-only modal identification methods. The identified modal parameters are examined with respect to at least two different conditions such as traffic- and typhoon-induced loadings. Finally, the typhoon-induced effects on dynamic characteristics of the bridge are estimated by analyzing the relationship between the wind velocity and the modal parameters.

• International Journal of Concrete Structures and Materials
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• 제2권2호
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• pp.91-98
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• 2008

Curved bridges are important components of a highway transportation network for connecting local roads and highways, but very few data have been collected in terms of their field performance. This paper presents two-years monitoring and system identification results of a curved concrete box-girder bridge, the West St. On-Ramp, under ambient traffic excitations. The authors permanently installed accelerometers on the bridge from the beginning of the bridge life. From the ambient vibration data sets collected over the two years, the element stiffness correction factors for the columns, the girder, and boundary springs were identified using the back-propagation neural network. The results showed that the element stiffness values were nearly 10% different from the initial design values. It was also observed that the traffic conditions heavily influence the dynamic characteristics of this curved bridge. Furthermore, a probability distribution model of the element stiffness was established for long-term monitoring and analysis of the bridge stiffness change.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.218-225
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• 2000

This paper presents intermediate results of an on-going research for identification of the modal and the stiffness parameters of a bridge based on the ambient vibration data caused by the traffic loadings. The main algorithms consist of the random decrement method incorporating band-pass filters for estimation of the free vibration signals the cross spectral density method for identification of the modal parameters and the neural networks technique for estimation of the element-level stiffness changes. An experimental study is carried out on a scaled bridge model with a composite section subjected to various moving vehicle loadings. Vertical accelerations are measured at several locations on the girder. The estimated frequencies and mode shapes are found to be well-compared with those obtained from the impact tests. The estimated stiffness changes using the neural networks are found to be very good for the case with the simulated data. However the accuracy is found to be not quite satisfactory for the case with the experimental data particularly for the small value of the stiffness changes.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.1037-1040
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• 2004

Sound and vibrations enter every aspect of our daily lives. Some, like music and verbal communications, soothe and relax us; others, such as the noise and vibration from traffic or machinery, can threaten our well being. The Rion Co., Ltd. was eslablished in 1944 as an affiliate of physics and acoustic pioneer, Kobayashi Institute of Physical Research. The RION lineup affords a full line of easy-to handle measuring, recording, and analyzing equipment with innumerable applications for monitoring and maintaining a comfortable environment. RION's concern takes in all manner of sound and vibration. Our activities extend from measuring reverberation time in concert halls and testing the soundproofing characteristics of housing materials to the control and maintenance of machine noise and vibration levels.

• 비파괴검사학회지
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• 제27권6호
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• pp.483-500
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• 2007

Emerging sensor-based structural health monitoring (SHM) technology can play an important role in inspecting and securing the safety of aging civil infrastructure, a worldwide problem. However, implementation of SHM in civil infrastructure faces a significant challenge due to the lack of suitable sensors and reliable methods for interpreting sensor data. This paper reviews recent efforts and advances made in addressing this challenge, with example sensor hardware and software developed in the author's research center. It is proposed to integrate real-time continuous monitoring using on structure sensors for global structural integrity evaluation with targeted NDE inspection for local damage assessment.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.89-101
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• 2006

This study is a part of ???A study of the community noise:new guideline and policy' which have three main topics and ten sub-topics. Accordingly this part deals with a transpotation noise specifying road traffic ,railroad and aircraft noise, respectively. At first, the ,roadside traffic noise of whole country in 2004 ,22 major cities of total 29 was exceeded the envionmetal noise standards, 55dB(A) at night time ,therefore 24 milion people ,52.4% of korean, who reside at roadside estimates to be exposured the basic problems of this serious noise polluation comes from:: i)It's very limited noise mitigation measures against to continuously increase the number of automobile yearly. ii) and at beginning of road design, It has been neglect to introduce the anti-noise design and layout of road structural scheme as gadient,cutting and viaduct,embankment and zonning of roadside land-buffer area and also re-designation of noise sensitive areas,etc. Secondly ,concerned with the railroad trafffic noise, a inhabitants who are over the envionmetal noise limits,70dB(A), 65 dB(A) in day and night for 34 locations of mayor cities was exposured of 167,000 and 329,000 respectively. With the development of noise mitigation schemes in line with this study it is likely that noise monitoring system needs new installation as well as common use of noise assessment index with $L_{MAX}\;and\;L_{EQ}$. Lastly,noise complaints of millitary aircraft has been rapidly increasing ,so 2.9%(1.4 minion) person demands a compansation of \2,133 billion complying with their requirements we suggest to minimise the airport noise that is to develop of noise abatement procedure ,to make new noise index, to increase budget for house insulations and also to more increase of those the noise monitoring system and to unify the management etc.

• 한국지반공학회지:지반
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• 제13권4호
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• pp.121-134
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• 1997

교통하중이나 건설 작업에 의해 야기되는 지반진동은 인접구조물에 손상을 입히거나 인근 주민들의 생활에 큰 불편을 야기할 수 있으므로 중요하게 측정, 관리되어야 한다. 지반진동으로 인해 발생하는 구조물의 손상은 진동의 직접 전파에 의한 구조물의 손상과 지반진동으로 야기된 지반의 부등 침하의 두 가지 원인으로 분류될 수 있다. 지반진동에 의한 피해를 효과적으로 줄이기 위해서는 현장에서의 정화한 진동의 측정이 필수적이다. 본 논문에서는 지반진동의 측정에 사용되어지는 대표적인 진동감지기인 속도계의 검증 방법에 대해 기술하였으며, 주파수대역 출력특성이 검증되어진 개개의 속도계로 부터 진동이 전파되는 매질인 지중에서 지반진동이 측정 가능한 3방향 진동 측정기를 제작하였고 진동측정기의 검증 및 운용법에 대하여 상세히 설명하였다. 또한 제작된 3방향 진동측정기로 열차진동, 말뚝항타진동 및 발파진동을 측정하여 적용성을 평가 하였다.