• Smart Structures and Systems
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• v.6 no.5_6
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• pp.579-593
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• 2010

Low-power radio frequency (RF) chip transceiver technology and the associated structural health monitoring platforms have matured recently to enable high-rate, lossless transmission of measurement data across large-scale sensor networks. The intrinsic value of these advanced capabilities is the allowance for high-quality, rapid operational modal analysis of in-service structures using distributed accelerometers to experimentally characterize the dynamic response. From the analysis afforded through these dynamic data sets, structural identification techniques can then be utilized to develop a well calibrated finite element (FE) model of the structure for baseline development, extended analytical structural evaluation, and load response assessment. This paper presents a case study in which operational modal analysis is performed on a three-span prestressed reinforced concrete bridge using a wireless sensor network. The low-power wireless platform deployed supported a high-rate, lossless transmission protocol enabling real-time remote acquisition of the vibration response as recorded by twenty-nine accelerometers at a 256 Sps sampling rate. Several instrumentation layouts were utilized to assess the global multi-span response using a stationary sensor array as well as the spatially refined response of a single span using roving sensors and reference-based techniques. Subsequent structural identification using FE modeling and iterative updating through comparison with the experimental analysis is then documented to demonstrate the inherent value in dynamic response measurement across structural systems using high-rate wireless sensor networks.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.66-73
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• 2024

Stay-cable is one of the most important load carrying members in cable-stayed bridges. Monitoring structural integrity of stay-cables is crucial for evaluating the structural condition of the cable-stayed bridge. For stay-cables, tension and damping ratio are estimated based on modal properties as a measure of structural integrity. Since the monitoring system continuously measures the vibration for the long-term period, data acquisition systems should be stable and power-efficiency as the hardware system. In addition, massive signals from the data acquisition systems are continuously generated, so that automated analysis system should be indispensable. In order to fulfill these purpose simultaneously, this study presents an autonomous cable monitoring system based on domain-knowledge using IoT for continuous cable monitoring systems of cable-stayed bridges. An IoT system was developed to provide effective and power-efficient data acquisition and on-board processing capability for Edge-computing. Automated peak-picking algorithm using domain knowledge was embedded to the IoT system in order to analyze massive data from continuous monitoring automatically and reliably. To evaluate its operational performance in real fields, the developed autonomous monitoring system has been installed on a cable-stayed bridge in Korea. The operational performance are confirmed and validated by comparing with the existing system in terms of data transmission rates, accuracy and efficiency of tension estimation.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.171-174
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• 2007

The COMS flight software is implemented by ADA language and the high level application program language (APL). The APL is used to implement the Interpreted Program (IP) functions which are running on the processor. The IP functions have been developed for the payload management and monitoring with the automatic on-board operational procedure. The IP allows an easier re-programming if necessary. The ground can load or unload IP separately from ADA code in the RAM flight software. The uploaded IP is interpreted and executed by the Interpreted Program Environment (IPE) which is one of the functions implemented in the RAM flight software. In this paper, we introduce the IP and IPE function.

• Journal of Environmental Science International
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• v.29 no.3
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• pp.299-306
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• 2020

This study analyzed the changes in the concentrations of the pollutants of constructed treatment wetlands which come from the discharge water of a sewage treatment plant. According to the results of budgets in constructed wetlands, the net production of the organic carbon, nitrogen and phosphorus were 368 kgC/month, 306 kgN/month and -49 kgP/month, respectively. The high particle form of pollutants are mostly removed due to settlement and absorption when passing through wetlands, but because a low processing efficiency for pollutants was shown when sewage treatment plant wastewater flows in, there is a need for a water management system that can reduce the organic matter load through monitoring. The low removal efficiency of constructed wetlands were caused by both structural and operational problems. Therefore, to enable to play a role as a reduction facility of pollutants, an appropriate design and operation manuals for constructed wetlands is urgently needed.

• Journal of Power Electronics
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• v.16 no.3
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• pp.1226-1235
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• 2016

For wearable health monitoring systems, a fundamental problem is the limited space for storing energy, which can be translated into a short operational life. In this paper, a highly efficient active voltage doubling rectifier with a wide input range for micro-piezoelectric energy harvesting systems is proposed. To obtain a higher output voltage, the Dickson charge pump topology is chosen in this design. By replacing the passive diodes with unbalanced-biased comparator-controlled active counterparts, the proposed rectifier minimizes the voltage losses along the conduction path and solves the reverse leakage problem caused by conventional comparator-controlled active diodes. To improve the rectifier input voltage sensitivity and decrease the minimum operational input voltage, two low power common-gate comparators are introduced in the proposed design. To keep the comparator from oscillating, a positive feedback loop formed by the capacitor C is added to it. Based on the SMIC 0.18-μm standard CMOS process, the proposed rectifier is simulated and implemented. The area of the whole chip is 0.91×0.97 mm², while the rectifier core occupies only 13% of this area. The measured results show that the proposed rectifier can operate properly with input amplitudes ranging from 0.2 to 1.0V and with frequencies ranging from 20 to 3000 Hz. The proposed rectifier can achieve a 92.5% power conversion efficiency (PCE) with input amplitudes equal to 0.6 V at 200 Hz. The voltage conversion efficiency (VCE) is around 93% for input amplitudes greater than 0.3 V and load resistances larger than 20kΩ.

• Structural Monitoring and Maintenance
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• v.10 no.1
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• pp.87-105
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• 2023

Seismic regulations have been updated from time to time to accommodate an increase in seismic hazards. Comparison of seismic fragility of the existing bridges in Indonesia from different historical periods since the era before 1990 will be the basis for seismic assessment of the bridge stock in Indonesia, most of which are located in earthquake-prone areas, especially those built many years ago with outdated regulations. In this study, seismic fragility curves were developed using incremental non-linear time history analysis and more holistically according to the actual strength of concrete and steel material in Indonesia to determine the uncertainty factor of structural capacity, βc. From the research that has been carried out, based on the current seismic load in SNI 2833:2016/Seismic Map 2017 (7% probability of exceedance in 75 years), the performance level of the bridge in the era before SNI 2833:2016 was Operational-Life Safety whereas the performance level of the bridge designed with SNI 2833:2016 was Elastic - Operational. The potential for more severe damage occurs in greater earthquake intensity. Collapse condition occurs at As = F_PGA x PGA value of bridge Era I = 0.93 g; Era II = 1.03 g; Era III = 1.22 g; Era IV = 1.54 g. Furthermore, the fragility analysis was also developed with geometric variations in the same bridge class to see the effect of these variations on the fragility, which is the basis for making bridge risk maps in Indonesia.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.715-730
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• 2023

Broad studies have addressed the issue of structural element damage identification, however, rubber bearing, as a key component of load transmission between the superstructure and substructure, is essential to the operational safety of a bridge, which should be paid more attention to its health condition. However, regarding the limitations of the traditional bearing damage detection methods as well as few studies have been conducted on this topic, in this paper, inspired by the model updating-based structural damage identification, a two-stage bearing damage identification method has been proposed. In the first stage, we deduce a novel bearing damage localization indicator, called element relative MSE, to accurately determine the bearing damage location. In the second one, the prior knowledge of bearing damage localization is combined with sailfish optimization (SFO) to perform the bearing damage estimation. In order to validate the feasibility, a numerical example of a 5-span continuous beam is introduced, also the noise robustness has been investigated. Meanwhile, the effectiveness and engineering applicability are further verified based on an experimental simply supported beam and actual engineering of the I-40 Bridge. The obtained results are good, which indicate that the proposed method is not only suitable for simple structures but also can accurately locate the bearing damage site and identify its severity for complex structure. To summarize, the proposed method provides a good guideline for the issue of bridge bearing detection, which could be used to reduce the difficulty of the traditional bearing failure detection approach, further saving labor costs and economic expenses.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1239-1244
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• 2023

In this study, we developed an IoT-based management system to manage a can/PET crusher. Various sensors such as two load cells, DHT22 temperature and humidity sensor, and fine dust meter were interfaced with ESP32 to construct an IoT device, and a management server was built using Node-RED. The system monitors the weight of pressed cans and shredded PET bottles in real time and sends a text message to the manager when the weight exceeds the predetermined threshold for timely collection. The results of the operational test confirmed that the system provides accurate monitoring and efficient notification functions, and offers the possibility of solving environmental problems by improving the efficiency of waste management such as cans and PET bottles.

• Structural Monitoring and Maintenance
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• v.4 no.1
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• pp.17-31
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• 2017

Since extensometers are used to determine the absolute deformation of foundation and abutments and all results are obtained in reference to the base rod, the accuracy of these results has been constantly a subject of debate. In this regard, locating and installing extensometers outside the range of effect zone is also another challenge. The main purpose of this paper is to investigate and modify extensometers results based on the mentioned issues. For this aim, the concrete RCC Zhaveh dam in Iran was selected as the case study. To study the results of extensometers installed in this dam, first, the 3DEC_DP 5.00 software was applied for numerical modeling. Parameters such as discontinuities, dead load and piezometric pressure in the interface of concrete and rock were considered. Next, using the results obtained from 6 extensometers in foundation and abutments and 4 clinometers in dam body, the numerical model was calibrated through back analysis method. The results indicate that the base rod is moved and is not recommended being used as the base point. In other words, because installation of base anchor outside the range of effect zone is not possible due to the operational and economic considerations, the obtained results are not accurate enough. The results indicate a considerable 2-3 mm displacement of the base rod (location of the base anchor) in reference to the real zero point location, which must be added to the base rod results.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.1
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• pp.93-102
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• 2005

A prototype surface flow constructed wetland was built in the upstream area of Sihwa reclaimed tidal lands to improve the water quality of Lake Sihwa by treating severely polluted stream water. In this study, we monitored hydrology, macrophyte (Phragmites communis Trin,) growth, and water quality in the Banwol and Donghwa wetlands to evaluate their performance during the initial period after the completion of wetland construction, The average removal efficiency($\%$) in each wetland was relatively low compared with the performance data from the North America Wetland Treatment System Database (NADB), which mainly includes urban sewage-treatment wetlands. However, the average removal rates per unit area ($g/m^{2}/day$) were 0.72, 0.72 and 0.51 (BOD), 2,04, 2.46 and 0.70 (SS), 0.89, 0.43 and 1.09 (TN) and 0.02, 0.02 and 0.02 (TP) in the Banwol and Donghwa wetlands and NADB, respectively. The overall performance of the Banwol and Donghwa wetlands was within the expected range of the wetland system processes contributing the reduction of the pollutant load to Lake Sihwa during the initial period of wetland operation. Considering the low influent concentration, high hydraulic loading rate, and insufficient macrophyte growth since the wetland was constructed, better performance is expected if an improved operational scheme is adopted.