• Smart Structures and Systems
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• 제29권1호
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• pp.53-62
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• 2022

The deployment of advanced structural health monitoring (SHM) systems in large-scale civil structures collects large amounts of data. Note that these data may contain multiple types of anomalies (e.g., missing, minor, outlier, etc.) caused by harsh environment, sensor faults, transfer omission and other factors. These anomalies seriously affect the evaluation of structural performance. Therefore, the effective analysis and mining of SHM data is an extremely important task. Inspired by the deep learning paradigm, this study develops a novel generative adversarial network (GAN) and convolutional neural network (CNN)-based data anomaly detection approach for SHM. The framework of the proposed approach includes three modules : (a) A three-channel input is established based on fast Fourier transform (FFT) and Gramian angular field (GAF) method; (b) A GANomaly is introduced and trained to extract features from normal samples alone for class-imbalanced problems; (c) Based on the output of GANomaly, a CNN is employed to distinguish the types of anomalies. In addition, a dataset-oriented method (i.e., multistage sampling) is adopted to obtain the optimal sampling ratios between all different samples. The proposed approach is tested with acceleration data from an SHM system of a long-span bridge. The results show that the proposed approach has a higher accuracy in detecting the multi-pattern anomalies of SHM data.

• 농업과학연구
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• 제47권4호
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• pp.1123-1134
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• 2020

The goal of this study was to develop an accelerated life test for an implement working pump for an agricultural tractor. The field experiments were conducted to measure the load of an implement working pump during major agricultural operations such as plow tillage, rotary tillage, baler operations, and wrapping operations. The measurement system for an implement working pump load was constructed using a pressure sensor, the engine rotational speed, and the hitch pump displacement. The measured implement working pump load was calculated as an equivalent load for each agricultural operation using the Palmgren-Miner rule, which is a cumulative damage method. The equivalent load was calculated using the total load data and peak load data when the total data included the operation of an implement working. The annual usage time of the agricultural tractor was applied to develop two integrated equivalent loads. The acceleration factor was calculated to develop an accelerated life test and was calculated from the two integrated equivalent loads, the maximum pressure, and the flow rate conditions of the hitch pump. In Korea, the warranty life of a tractor is 2,736 hours, and the time required for the test to guarantee the operational life of tractors was calculated as 7,561 hours. The acceleration factors were calculated as 453.6 and 38.3, respectively, from the total load data and peak load data. The fatigue test time can be shortened by 16.7 and 197.4 hours according to the result of the acceleration factors.

• Wind and Structures
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• 제20권2호
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• pp.249-274
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• 2015

Long-span cable-stayed bridges exhibit some features which are more critical than typical long span bridges such as geometric and aerodynamic nonlinearities, higher probability of the presence of multiple vehicles on the bridge, and more significant influence of wind loads acting on the ultra high pylon and super long cables. A three-dimensional nonlinear fully-coupled analytical model is developed in this study to improve the dynamic performance prediction of long cable-stayed bridges under combined traffic and wind loads. The modified spectral representation method is introduced to simulate the fluctuating wind field of all the components of the whole bridge simultaneously with high accuracy and efficiency. Then, the aerostatic and aerodynamic wind forces acting on the whole bridge including the bridge deck, pylon, cables and even piers are all derived. The cellular automation method is applied to simulate the stochastic traffic flow which can reflect the real traffic properties on the long span bridge such as lane changing, acceleration, or deceleration. The dynamic interaction between vehicles and the bridge depends on both the geometrical and mechanical relationships between the wheels of vehicles and the contact points on the bridge deck. Nonlinear properties such as geometric nonlinearity and aerodynamic nonlinearity are fully considered. The equations of motion of the coupled wind-traffic-bridge system are derived and solved with a nonlinear separate iteration method which can considerably improve the calculation efficiency. A long cable-stayed bridge, Sutong Bridge across the Yangze River in China, is selected as a numerical example to demonstrate the dynamic interaction of the coupled system. The influences of the whole bridge wind field as well as the geometric and aerodynamic nonlinearities on the responses of the wind-traffic-bridge system are discussed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.258-261
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• 1997

The sealing integrity is related to the safe operation of arrester the prime failure reason of porcelain housed arresters is moisture ingress. To be a meaningful tests a polymer arrester sealing test must be a realistic acceleration of field service. We think the test should be an accelerating course of actual temperatures, the enduring property to mechanical load and temperatures should be considered together. A union test method consisting of the thermal mechanical test and thermal cycling test is proposed to test the sealing integrity of polymeric arresters, which uses dielectric loss, leakage current 1mA DC voltage and partial discharge as the diagnostic techniques, and the test results were presented. The comparison states that the TMTCUT method is suitable fur the test of sealing integrity of polymeric arresters. .

• 한국도로학회논문집
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• 제14권4호
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• pp.73-81
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• 2012

PURPOSES : The purpose of this study is to select the proper sealing method and to see the performance of the saw and seal method for concrete rehabilitation based on accelerated pavement testings and lab tests. METHODS : Two accelerated pavement testings were conducted. One is to select proper sealing method of the asphalt joints and the other is to see the performance of the saw and seal method. Lab tests were conducted to select proper sealing method and a test section was constructed to see the field performance. RESULTS : The result of the first accelerated pavement testing indicated that the adhesive preformed sealants showed good performance when asphalt layer was rutted and in terms preventing from water infiltration. The second acceleration test indicated that the saw and seal method using the adhesive preformed sealant showed much better performance than the control. In the lab test bitumen, rubber and epoxy showed good performance as the adhesive. CONCLUSIONS : Saw and Seal method using the adhesive preformed sealant would markedly reduce the joint damage on the asphalt overlay.

• 전자공학회논문지A
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• 제32A권1호
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• pp.146-151
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• 1995

We have studied the fabrication self aligned atmospheric pressure(AP) CVD a-Si thin film transistor with source-drain ohmic contact by using ion shower doping method. The conductivity is 6*10$^{-2}$S/cm when the acceleration voltage, doping time and doping temperature are 6kV, 90s and 350.deg. C, respectively. We obtained the field effect mobility of 1.3cm$^{2}$/Vs and the threshold voltage of 7V.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.321-323
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• 2015

Monitoring crane motion in real time is the first step to identifying and mitigating crane-related hazards on construction sites. However, no accurate and reliable crane motion capturing technique is available to serve this purpose. The objective of this research is to explore a method for real-time crane motion capturing and investigate an approach for assisting hazard detection. To achieve this goal, this research employed various techniques including: 1) a sensor-based method that accurately, reliably, and comprehensively captures crane motions in real-time; 2) computationally efficient algorithms for fusing and processing sensing data (e.g., distance, angle, acceleration) from different types of sensors; 3) an approach that integrates crane motion data with known as-is environment data to detect hazards associated with lifting tasks; and 4) a strategy that effectively presents crane operator with crane motion information and warn them with potential hazards. A prototype system was developed and tested on a real crane in a field environment. The results show that the system is able to continuously and accurately monitor crane motion in real-time.

• Interaction and multiscale mechanics
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• 제3권2호
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• pp.173-191
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• 2010

Damage detection plays a very important role to the maintenance of bridge structures. Traditional damage detection methods are usually based on structural dynamic properties, which are acquired from pre-installed sensors on the bridge. This is not only time-consuming and costly, but also suffers from poor sensitivity to damage if only natural frequencies and mode shapes are concerned in a noisy environment. Recently, the idea of using the dynamic responses of a passing vehicle shows a convenient and economical way for damage detection of bridge structures. Inspired by this new idea and the well-established tap test in the field of non-destructive testing, this paper proposes a new method for obtaining the damage information through the acceleration of a passing vehicle enhanced by a tapping device. Since no finger-print is required of the intact structure, this method can be easily implemented in practice. The logistics of this method is illustrated by a vehicle-bridge interaction model, along with the sensitivity analysis presented in detail. The validity of the method is proved by some numerical examples, and remarks are given concerning the potential implementation of the method as well as the directions for future research.

• 한국철도학회논문집
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• 제9권2호
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• pp.160-168
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• 2006

The major objective of this study is to investigate the effects and application of external post-tensioning method far steel plate girder bridge. It analyzed the mechanical behaviors of steel plate girder bridge with applying external post-tensioning on the finite element analysis, field test and laboratory test fur the lateral dynamic characteristics. As a result, the reinforcement of steel plate girder bridge the external post-tensioning method are obviously effective for the lateral dynamic response which is non-reinforced. The analytical and experimental study are carried out to investigate the post-tension force decrease lateral acceleration and deflection on steel plate girder bridge for serviceability. And the external post-tensioning method reduce dynamic maximum displacement(about $10{\sim}24%$), the increase of dynamic safety is predicted by adopting external post-tensioning method. From the dynamic test results of the servicing steel plate girder bridge, it is investigated that the change degree of natural frequency is very low with applying the external post-tensioning method The servicing steel plate girder bridge with external post-tensioning has need of the reasonable reinforcement measures which could be reducing the effect of lateral dynamic behavior that degradation phenomenon of structure by an unusual response characteristic and a drop durability.

• 대한교통학회지
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• 제20권1호
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• pp.121-130
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• 2002

본 연구의 목적은 도로의 안전성 평가 방법을 제시하여 안전성 평가 기준을 확립하는데 기여하고 궁극적으로 도로 안전에 기여하는 데 있다. 연구는 사고자료와 현장자료(종단경사, 곡선반경. 속도특성)를 수집하고, EXCEL과 SPSS를 이용하여 정리되고 분석되었다. 문헌고찰에서 기존 안전성 평가방법의 문제점과 수집된 자료 분석의 결과를 가지고 새로운 안전성 평가 방법을 제시하였다. 제시된 안전성 평가 방법은 기존 방법과의 비교를 통하여 그 타당성을 검증하였다. 연구 수행으로 얻어진 결과는 다음과 같다. 1)속도분산차,. 차량 진행방향 가속도차, 곡선반경방향 가속도차를 이용하여 새로운 안전성 평가 방법을 제시하였다. 2)속도 차, 에너지 차. 본 논문에서 제시한 안전성 평가 방법을 현장 조사된 지점을 대상으로 비교하고, 제시된 방법이 더 적절하다는 결과를 얻었다. 3)선행차량에 의해 속도 영향을 받는 차두간격은 6초 이하이다 4)곡선부 내의 최저 속도 위치는 곡선시작점으로부터 약 35m 이다. 5)도로의 위험도(EPDO)와 통계적으로 유의한 상관관계를 보이는 속도특성은 속도분산이다. 그러나 제시된 안전성 평가의 현장 적용을 위해서는 기하구조가 다른 많은 지점에 대한 연구로 평가 방법을 재검증하고, 각 기준별 등급과 가중치에 대한 연구가 수행되어져야 할 것이다.