Sensors In Concrete Structures Research Articles

Dynamic matching error of stress sensors in concrete structures

The matching error between the sensors and media is an important factor in determining the reliability of measurement results. To investigate the dynamic matching error between the sensors and the media, the causes of static and dynamic matching errors and their influence trend are theoretically analyzed in this study; and the dynamic matching error between the sensor and the concrete structure under explosion load through test and numerical simulation are quantitatively analyzed. Our results show that the difference between the wave impedance of the sensor and the medium is the main factor affecting the dynamic matching error; the static matching error is usually constant, while the dynamic matching error is a variable related to the stress wavelength. A larger ratio of the stress wavelength to the thickness of the sensor correlates to a lower dynamic matching error. The dynamic matching error with the stress signal rise time increases and decreases.

Interfacial Effect on Quantitative Concrete Stress Monitoring via Embedded PZT Sensors Based on EMI Technique

Sensing performance is crucial for real-world applications of the embedded piezoelectric lead zirconate titanate (PZT) sensors in concrete structures. Based on the electromechanical impedances (EMIs) obtained numerically and experimentally from the embedded PZT sensors, effects of installation orientation and interfacial roughness were investigated on their sensitivity and reliability for quantitative concrete stress monitoring. The numerical results suggest a better sensitivity in the embedded 90° PZT sensors, with planar normal perpendicular to the loading direction, where the conductance amplitude variation is 6.5 times of that of the 0° PZT sensors, with normal parallel to load direction. Further, the improved reliability of the PZT sensors with rough interfaces is observed experimentally, which makes them robust for concrete stress monitoring over a wider sensing range from 0 to 20 MPa. Based on the static analyses, it is noted that the sensing performance of the embedded sensor is significantly affected by the interfacial stiffness degradation induced by the enhanced strain surrounding the sensor. These findings suggest that delaying the interfacial stiffness degradation, i.e., with proper installation orientation and interfacial treatment, could improve the sensing performance of the embedded sensors for quantitative concrete stress monitoring.

Comparative Analysis between Genetic Algorithm and Simulated Annealing-Based Frameworks for Optimal Sensor Placement and Structural Health Monitoring Purposes

The arbitrary placement of sensors in concrete structures measures a considerable amount of unnecessary data. Optimal sensor placement methods are used to provide informative data with the least cost and maximum efficiency. In this study, a robust optimal sensor placement framework that combines an optimization-based algorithm, the simulated annealing (SA) algorithm, and the ensemble Kalman filter (EnKF) are presented for structural health monitoring and system identification. The SA algorithm randomly generates an initial population of sensor locations, while the framework undergoes a minimization process. The objective function used is the difference between the actual measured data and their corresponding EnKF predicted values. A comparative analysis between the genetic algorithm–ensemble Kalman filter (GA-EnKF) and the simulated annealing–ensemble Kalman filter (SA-EnKF) approaches is presented. The performance and computational burden of both algorithms, which converge to the best sensor locations for damage detection purposes, are tested on a 10-story building subjected to a seismic excitation. The results are compared to the optimal sensor locations of the brute-force search methodology. The GA-EnKF outperforms the SA-EnKF in terms of accuracy in converging to the optimal results, yet the computational cost of the SA-EnKF is considerably lower.

Behavior of capacitive humidity sensors in monitoring the drying of concrete walls

This research examines the behavior of capacitive humidity sensors in monitoring the drying of concrete walls in continuous measurements in laboratory conditions. Tests are carried out using continuous measuring of moisture with different capacitive sensors in concrete structures varied with three different types of thermal insulation materials. Sensors are sealed in plastic tubes that were preinstalled into the casting molds. Three borehole measurements are carried out as reference during the research. Results show differences in performance between the examined humidity sensors from two different manufacturers. The main difference is related to stability as sensors from the other manufacturer prove to be more prone to error. The study affirms that measuring humidity in concrete is challenging even when using high-quality humidity sensors.

Distributed optical fibre sensors in concrete structures: Performance of bonding adhesives and influence of spatial resolution

This is the accepted version of the following article: [Barrias, A, Casas, JR, Villalba, S. Distributed optical fibre sensors in concrete structures: Performance of bonding adhesives and influence of spatial resolution. Struct Control Health Monit. 2019; 26:e2310. https://doi.org/10.1002/stc.2310], which has been published in final form at https://onlinelibrary.wiley.com/doi/abs/10.1002/stc.2310

Examples of reinforcement corrosion monitoring by embedded sensors in concrete structures

Abstract An increasing number of concrete structures are being monitored to enhance their durability. However, the literature provides only some guidance for the interpretation of the monitoring results [Broomfield JP. Corrosion of steel in concrete, understanding investigation and repair. 2nd ed. UK: Taylor & Francis; 2006; Andrade C, Alonso C. On-site measurements of corrosion rate of reinforcements. Constr Build Mater 2001;15(2–3):141–45; EN 206 2000. Concrete—Part 1: specification, performance, production and conformity]. Past experience shows the difficulty of interpreting the data collected due to the influence of temperature and moisture, and of using these data to predict future evolution of any deterioration processes. This paper presents several examples of recorded data for corrosion potential, electrical resistance and corrosion rates, along with a methodology to obtain a representative corrosion rate, averaged per year. The representative value can be used in corrosion predictive models to calculate the remaining service life.

Fiber optic sensors in concrete: the future?

Fiber optic sensing systems have been successfully developed for many engineering applications. The objective of this review paper is to assess the potential of fiber optic sensors for the monitoring of concrete structures. In this paper, some current applications of fiber optic sensors in concrete structures are first reviewed to demonstrate their applicability in conventional monitoring applications. The advantages of optical sensors over electrical gauges and transducers are also discussed. Then, we will focus on two novel fiber optic sensors for the monitoring of cracking and delamination in concrete structures without requiring a priori knowledge of the damage locations. Through these two examples, it is demonstrated that the proper design of optic sensors can provide useful sensing capabilities unprecedented with conventional sensors. With further research focusing on the development of novel sensing concepts and the reduction of sensor cost, the widespread use of optical sensors in concrete structures can become a reality in the future.

Fiber optic sensors in concrete structures: a review

Fiber optic sensors (FOSs) are ideally suited for monitoring strain in concrete structures due to their small size, low cost, ability to be embedded internally, and multiplexing capabilities. Several types of fiber optic strain sensor have been developed, including those based on intensity, polarization, interferometry, and fiber Bragg gratings (FBGs). The FBGs have the advantage of being absolute, linear in response, interrupt immune, and most readily multiplexed. The ability of embedded and surface mounted FOSs to detect strain in reinforced concrete has been demonstrated in several laboratory tests. Comparisons between various FOSs and traditional foil strain gages show good agreement. Sensors have been surface mounted on existing bridges to evaluate observed cracking and to monitor vibration due to traffic loading. FOSs have also been embedded in several newly constructed civil structures, including bridges, buildings, and dams, yielding information about static and dynamic strain, temperature, wind or water pressure, and structural health. Practical and logistical challenges to routine implementation of FOSs in civil structures are being addressed with each additional application.