Low-Cost Technologies Used in Corrosion Monitoring.

Globally, corrosion is the costliest cause of the deterioration of metallic and concrete structures, leading to significant financial losses and unexpected loss of life. Therefore, corrosion monitoring is vital to the assessment of structures' residual performance and for the identification of pathologies in early stages for the predictive maintenance of facilities. However, the high price tag on available corrosion monitoring systems leads to their exclusive use for structural health monitoring applications, especially for atmospheric corrosion detection in civil structures. In this paper a systematic literature review is provided on the state-of-the-art electrochemical methods and physical methods used so far for corrosion monitoring compatible with low-cost sensors and data acquisition devices for metallic and concrete structures. In addition, special attention is paid to the use of these devices for corrosion monitoring and detection for in situ applications in different industries. This analysis demonstrates the possible applications of low-cost sensors in the corrosion monitoring sector. In addition, this study provides scholars with preferred techniques and the most common microcontrollers, such as Arduino, to overcome the corrosion monitoring difficulties in the construction industry.

Operational and Analytical Modal Analysis of a Bridge Using Low-Cost Wireless Arduino-Based Accelerometers.

Arduino-based accelerometers are receiving wide attention from researchers to make long-term Structural Health Monitoring (SHM) feasible for structures with a low SHM budget. The current low-cost solutions found in the literature share some of the following drawbacks: (1) high noise density, (2) lack of wireless synchronization, (3) lack of automatic data acquisition and data management, and (4) lack of dedicated field tests aiming to compare mode shapes from Operational Modal Analysis (OMA) with those of a digital model. To solve these problems, a recently built short-span footbridge in Barcelona is instrumented using four Low-cost Adaptable Reliable Accelerometers (LARA). In this study, the automatization of the data acquisition and management of these low-cost solutions is studied for the first time in the literature. In addition, a digital model of the bridge under study is generated in SAP2000 using the available drawings and reported characteristics of its materials. The OMA of the bridge is calculated using Frequency Domain Decomposition (FDD) and Covariance Stochastic Subspace Identification (SSI-cov) methods. Using the Modal Assurance Criterion (MAC), the mode shapes of OMA are compared with those of the digital model. Finally, the acquired eigenfrequencies of the bridge obtained with a high-precision commercial sensor (HI-INC) showed a good agreement with those obtained with LARA.

A Novel Wireless Low-Cost Inclinometer Made from Combining the Measurements of Multiple MEMS Gyroscopes and Accelerometers.

Structural damage detection using inclinometers is getting wide attention from researchers. However, the high price of inclinometers limits this system to unique structures with a relatively high structural health monitoring (SHM) budget. This paper presents a novel low-cost inclinometer, the low-cost adaptable reliable angle-meter (LARA), which combines five gyroscopes and five accelerometers to measure inclination. LARA incorporates Internet of Things (IoT)-based microcontroller technology enabling wireless data streaming and free commercial software for data acquisition. This paper investigates the accuracy, resolution, Allan variance and standard deviation of LARA produced with a different number of combined circuits, including an accelerometer and a gyroscope. To validate the accuracy and resolution of the developed device, its results are compared with those obtained by numerical slope calculations and a commercial inclinometer (HI-INC) in laboratory conditions. The results of a load test experiment on a simple beam model show the high accuracy of LARA (0.003 degrees). The affordability and high accuracy of LARA make it applicable for structural damage detection on bridges using inclinometers.

Low-Cost Wireless Structural Health Monitoring of Bridges.

Nowadays, low-cost accelerometers are getting more attention from civil engineers to make Structural Health Monitoring (SHM) applications affordable and applicable to a broader range of structures. The present accelerometers based on Arduino or Raspberry Pi technologies in the literature share some of the following drawbacks: (1) high Noise Density (ND), (2) low sampling frequency, (3) not having the Internet's timestamp with microsecond resolution, (4) not being used in experimental eigenfrequency analysis of a flexible and a less-flexible bridge, and (5) synchronization issues. To solve these problems, a new low-cost triaxial accelerometer based on Arduino technology is presented in this work (Low-cost Adaptable Reliable Accelerometer-LARA). Laboratory test results show that LARA has a ND of 51 µg/√Hz, and a frequency sampling speed of 333 Hz. In addition, LARA has been applied to the eigenfrequency analysis of a short-span footbridge and its results are compared with those of a high-precision commercial sensor.

Development of a Low-Cost System for the Accurate Measurement of Structural Vibrations.

Nowadays, engineers are widely using accelerometers to record the vibration of structures for structural verification purposes. The main obstacle for using these data acquisition systems is their high cost, which limits its use to unique structures with a relatively high structural health monitoring budget. In this paper, a Cost Hyper-Efficient Arduino Product (CHEAP) has been developed to accurately measure structural accelerations. CHEAP is a system that is composed of five low-cost accelerometers that are connected to an Arduino microcontroller as their data acquisition system. Test results show that CHEAP not only has a significantly lower price (14 times cheaper in the worst-case scenario) compared with other systems used for comparison but also shows better accuracy on low frequencies for low acceleration amplitudes. Moreover, the final output results of Fast Fourier Transformation (FFT) assessments showed a better observable resolution for CHEAP than the studied control systems.

Role of Sensors in Error Propagation with the Dynamic Constrained Observability Method.

The inverse problem of structural system identification is prone to ill-conditioning issues; thus, uniqueness and stability cannot be guaranteed. This issue tends to amplify the error propagation of both the epistemic and aleatory uncertainties, where aleatory uncertainty is related to the accuracy and the quality of sensors. The analysis of uncertainty quantification (UQ) is necessary to assess the effect of uncertainties on the estimated parameters. A literature review is conducted in this paper to check the state of existing approaches for efficient UQ in the parameter identification field. It is identified that the proposed dynamic constrained observability method (COM) can make up for some of the shortcomings of existing methods. After that, the COM is used to analyze a real bridge. The result is compared with the existing method, demonstrating its applicability and correct performance by a reinforced concrete beam. In addition, during the bridge system identification by COM, it is found that the best measurement set in terms of the range will depend on whether the epistemic uncertainty involved or not. It is concluded that, because the epistemic uncertainty will be removed as the knowledge of the structure increases, the optimum sensor placement should be achieved considering not only the accuracy of sensors, but also the unknown structural part.

Long-term impact of an educational antimicrobial stewardship programme in primary care on infections caused by extended-spectrum ß-lactamase-producing Escherichia coli in the community: an interrupted time-series analysis.

BACKGROUND: There is little evidence on the ecological effect and sustainability of antimicrobial stewardship programmes (ASPs) in primary-care settings. We aimed to determine whether a multimodal, educational ASP would be sustainable in the long-term and reduce the incidence of infections caused by extended-spectrum ß-lactamase-producing Escherichia coli in the community by optimising antibiotic use. METHODS: We did this quasi-experimental intervention study in 214 primary health centres of four primary health-care districts in Andalusia, Spain. Local multidisciplinary teams, comprised of general practitioners, paediatricians, primary-care pharmacists, and epidemiologists, were created in each district and implemented a multimodal, education-based ASP. The core activity of the programme consisted of regular one-to-one educational interviews between a reference interviewing physician and prescribing physicians from each centre on the appropriateness of their most recent (same or preceding day) antibiotic prescriptions based on a structured questionnaire. Appropriate prescribing was defined as compliance of all checklist items with the reference guidelines. An average of five educational interviews were scheduled per prescriber per study year. We did an interrupted time-series analysis to assess the effect of the intervention on quarterly antibiotic use (prescription and collection by the patient) and quality of prescriptions (as defined daily doses per 1000 inhabitants per day) and incidence per 1000 inhabitants of E coli producing extended-spectrum ß-lactamase (ESBL) isolated from urine samples. FINDINGS: The study was done between January, 2012, and December, 2017, in a pre-intervention period of 2012-13 and an intervention period of 2014-17. Throughout the study period, there were 1387 physicians (1116 general practicioners and 271 paediatricians) in the included health centres serving a mean population of 1 937 512 people (299 331 children and 1 638 181 adults). 24 150 educational interviews were done over the 4 years. Inappropriate antibiotic prescribing was identified in 1794 (36·5%) of 4917 educational interviews in 2014 compared with 1793 (26·9%) of 6665 in 2017 (p<0·0001). The intervention was associated with a sustained reduction in the use of ciprofloxacin (relative effect -15·9%, 95% CI -23·9 to -8·0) and cephalosporins (-22·6%, -35·9 to -9·2), and a sustained increase in the use of amoxicillin (22·2%, 6·4 to 38·0) and fosfomycin trometamol (6·1%, 2·6 to 9·6). The incidence density of ESBL-producing E coli decreased by -0·028 cases per 1000 inhabitants (95% CI -0·034 to -0·021) after the start of the programme, reversing the pre-intervention increase and leading to a relative reduction of -65·6% (-68·2 to -63·0) 4 years later. INTERPRETATION: Our data suggest that implementation of a multimodal ASP in primary care that is based on individual educational interviews improves the use of antibiotics and results in a sustained significant reduction of infections by ESBL-producing E coli in the community. This information should encourage the implementation of ASPs in primary care. FUNDING: Instituto de Salud Carlos III, Spanish Government (PI14/01523).