PSI - Issue 64

M. Komary et al. / Procedia Structural Integrity 64 (2024) 1311–1317 Mahyad Komary/ Structural Integrity Procedia 00 (2019) 000 – 000

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Recent trends in SHM programs have seen a growing interest among researchers in leveraging low-cost sensors and electronics to address traditional challenges in monitoring concrete structures. The utilization of low-cost sensors in SHM signifies a paradigm shift towards more economically feasible and scalable monitoring solutions with the possibility of increasing measuring points, thus resulting in the improvement of the resolution of the captured data. These sensors, coupled with innovative deployment strategies and enhanced through sophisticated programming codes [2], are beginning to match, and in some instances, surpass the performance of their more expensive counterparts. Table 2 highlights several instances where researchers have successfully employed low-cost sensors to monitor various parameters of concrete structures. One of the significant hurdles in adopting low-cost sensors has been concerns over their accuracy and reliability. However, recent studies demonstrate that through the application of powerful programming codes and algorithms, it is possible to calibrate these sensors and significantly improve their data fidelity [3]. This methodological advancement not only extends the utility of low-cost sensors but also opens up new avenues for their application in critical monitoring tasks.

Table 2. Overview of Low-Cost Sensor Technologies in SHM applications. Sensor Type Application Measured Parameters

Benefits

Reference

MEMS Accelerometers

Vibration-based damage detection in buildings and bridges Monitoring tilts and deformations in structures Assessing environmental impact on structural health

Acceleration, Displacement

Compact, and easy to install; Suitable for dynamic analysis of structures

[4][5]

MEMS Inclinometers Environmental sensors

Tilt, Angular Displacement

High precision in detecting subtle shifts and structural deformations; Helps in understanding environmental contributions to structural degradation

[6][7][8]

Temperature, Humidity, corrosion, Solar radiation

[9][10][11]

The integration of IoT technology in the context of SHM represents a significant advancement, enabling real-time data collection and analysis. This capability is particularly beneficial for early-stage concrete monitoring, where real time data on temperature and humidity can provide insights into the curing process, potentially influencing decision making and intervention strategies. Despite the promising developments in the use of low-cost sensors and IoT technologies, there remains a gap in their application specifically tailored for early-stage concrete monitoring. This research aims to bridge this gap by developing a low-cost IoT-based system utilizing the DHT22 temperature and humidity sensor in conjunction with the NodeMCU microcontroller coupled with a built-in Wifi Module. The objective is to demonstrate the feasibility of employing such a system to provide accurate, real-time temperature and humidity readings, and to leverage the IoT capabilities of the ThingSpeak platform for data visualization and analysis. This approach underscores the potential of low-cost sensors and IoT technology in revolutionizing early-stage concrete monitoring, making it more accessible and actionable for stakeholders across the construction industry. 3. Methodology This study employs a concise and focused methodology to explore the viability of a low-cost IoT-based sensor system for early-stage concrete monitoring, incorporating the DHT22 sensor and the NodeMCU microcontroller. The methodology encompasses the production and preparation of concrete specimens, detailing the sensor and microcontroller specifications, system integration, and data collection process. 3.1. Concrete Specimens The research utilized 12 hybrid polypropylene fibre-reinforced concrete beams (H-PPFRC) with dimensions of 150 × 150 × 600 mm³ and 9 additional polypropylene fibre reinforced concrete (PPFRC) elements for material characterization. Table 3 shows mix proportions of concrete elements used in the experimental program which should satisfy structural requirements for typical applications in contemporary civil engineering practice. Specifically, the H PPFRC specimens are designed to enhance the mechanical properties and durability for structural applications, necessitating a higher fibre content. However, the PPFRC specimens serve as a control group for material characterization, which typically involves lower fibre content to establish baseline properties. These specimens were