Browsing by Author "Vishnu, P"

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item: Conference-Abstract
Advanced structural health monitoring system for bridges in Sri Lanka
(Department of Civil Engineering, University of Moratuwa, Sri Lanka., 2021-11) Rajapaksha, D; Lewangamage, CS; Vishnu, P; Hettiarachchi, P
Bridges are a critical component of the transportation infrastructure system because a failure in a particular bridge may affect a wide range of areas adversely. Also, the intensity and frequency of natural shocks and stresses that can affect the performance of the bridges, such as earthquakes, floods, and tsunami have rapidly increased during the past few years, which increases the vulnerability of bridges by combining with aging. Hence it is crucial to monitor the current health of bridges so that devastating failures could be avoided by following a structured maintenance program. In that case, advanced Structural Health Monitoring (SHM) systems that are rapidly developing for past decades with the development of IoT, have been used for bridge monitoring purposes in other countries. However, the condition of the bridge monitoring system is not so developed in Sri Lanka yet. Also, the commonly used methods such as visual inspection and traditional tethered methods are incorporated with some drawbacks. Therefore, the requirement for an advanced SHM system for bridge monitoring in Sri Lanka has been raised. In this study, a low-cost wireless synchronous sensor network developed by the Department of Civil Engineering, University of Moratuwa was applied and monitored on a bridge as a pioneering step of implementing an advanced online SHM system for bridges in Sri Lanka. Here, the synchronous vibration time history of the structure was measured using the sensor network with high accuracy. After a filtration process, the data was applied for calculating the experimental modal parameters such as natural frequencies and mode shapes using Fast Fourier Transformation (FFT) and peak picking method. Finally, the experimental results were compared with the results of Finite Element Analysis (FEA) through the Modal Assurance Criteria (MAC). The MAC analysis showed values greater than 0.84 for the first four modes shapes which indicates a good correlation with the experimental results and the FEA results. Furthermore, the measured acceleration data was used to assess the serviceability state of the bridge as well.
item: Conference-Full-text
Development of low-cost wireless sensor network and online data repository system for time synchronous monitoring of civil infrastructures
(IEEE, 2020-07) Vishnu, P; Lewangamage, CS; Jayasinghe, MTR; Kumara, KJC; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Advances in wireless sensor networks (WSN) are well proven and commonly used in Structural Health Monitoring (SHM). SHM using WSN is the modern paradigm which incorporates automated systems for data acquisition, in monitoring, analysis, and identification of structural responses and defects. Even though currently used WSN are economical compared to tethered monitoring systems, it is still unaffordable. The costly nature of traditional data loggers and the low penetration nature of currently used networking protocols, through civil structures thus requiring dense array of sensors, increase the overall cost of a WSN. This paper discusses the development of a low cost WSN to monitor the acceleration response of civil engineering structures using off the shelf products. The developed system is capable of capturing synchronous acceleration response data with the sampling frequency of 100 Hz with a resolution of 0.5 mg. The collected data is processed and shared between peer nodes using sub 1 Gigahertz wireless protocol, and stored within an online based central data repository system replacing traditional data loggers. The developed low cost WSN is proved to be a better low cost alternative in the context of a target building with 48 floors (185 m height).
item: Conference-Full-text
Synchronized sensing and network scalability of low-cost wireless sensor networks for monitoring civil infrastructures
(IEEE, 2020) Vishnu, P; Radershan, S; Lewangamage, CS; Jayasinghe, MTR; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Applications of wireless sensor networks (WSN) in monitoring civil engineering structures have increased exponentially in the recent past, especially in monitoring high rise buildings. Capturing the global behavior of the structure (e.g. modal periods, mode shapes) using ambient response has become very common due to its applications in large number of damage detection methods. WSN is preferred over traditional tethered systems, mainly due to its dynamic nature and scalability. Capacity of handling large scale data and synchronized sensing are the two main aspects required for the efficiency of the WSN. The upper bound of the time synchronization error (jitter) in WSN should be kept in μs range in order to capture the modal behavior of the structures accurately. Currently, state of the art synchronization protocols that are used for this purpose, are not suitable for the low cost wireless sensor networks because those are radio driven, where the radio core and the CPU core are found separately. This paper discusses about the synchronized sensing method developed for low cost WSN. This protocol is proved to have less than 120 μs jitter and its implementation is discussed in the context of a target building with 48 floors (185 m high).
item: Conference-Full-text
Using sub-giga hertz technology in high sampling rate wireless monitoring systems used in high-rise buildings
(IEEE, 2021-07) Vishnu, P; Kirishikesan, K; Lewangamage, CS; Jayasinghe, MTR; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
Structural Health Monitoring (SHM) systems have been increasingly used in Civil Infrastructures to extract reliable information about the integrity and other important parameters of the structure in real-time. Using wireless sensor networks (WSN) in SHM applications has seen exponential growth in the last decade with the introduction of new communication protocols. WSN makes monitoring of structures easy and fast with low-cost involved. However, some structures such as high-rise buildings, are considered difficult for establishing WSN due to the presence of vertical obstructions. Radio waves with low-frequency are widely used in long-range SHM applications and monitoring high-rise buildings. Carrier waves with lower frequencies used in WSN travel over long-range and through obstructions easily compared to waves that are with higher frequency. Even though the range is increased in low-frequency waves, data rate is also reduced with decreasing frequency. In the SHM applications of high-rise buildings, it is not possible to compensate one - data transfer rate and penetrating ability for the other. This paper discusses the applications of Sub-Giga hertz technology and the corresponding performance of the developed WSN. Also, the application of simple and efficient data handling method used to ensure near real-time SHM is discussed in this paper.