Optical sensors for structural health monitoring

Public road infrastructure is developed all around the world. To save resources, ensure public safety, and provide longer-lasting road infrastructure, structural health monitoring (SHM) applications for roads have to be researched and developed. Asphalt is one of the largest used surface materials for the road building industry. This material also provides relatively easy fiber optical sensor technology installment, which can be effectively used for SHM applications—road infrastructure monitoring as well as for resource optimization when road building or their repairs are planned. This article focuses on the research of the fiber Bragg grating (FBG) optical temperature and strain sensor applications in road SHM, which is part of the greater interdisciplinary research project started at the Riga Technical University in the year 2017. Experimental work described in this article was realized in one of the largest Latvian road sites where the FBG strain and temperature sensors were installed into asphalt pavement, and experiments were carried out in two main scenarios. Firstly, in a controlled environment with a calibrated falling weight deflectometer (FWD) to test the installed FBG sensors. Secondly, by evaluating the real-time traffic impact on the measured strain and temperature, where different types of vehicles passed the asphalt span in which the sensors were embedded. The findings in this research illustrate that by gathering and combining data from calibrated FWD measurements, measurements from embedded FBG optical sensors which were providing the essential information of how the pavement structure could sustain the load and information about the traffic intensity on the specific road section, and the structural life of the pavement can be evaluated and predicted. Thus, it enables the optimal pavement future design for necessary requirements and constraints as well as efficient use, maintenance, and timely repairs of the public roads, directly contributing to the overall safety of our transportation system.

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Application of Smart FRP Devices for the Structural Health Monitoring of Heritage Buildings - A Case Study: The Monastery of Sant’Angelo d’Ocre

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.747.448 ◽

2017 ◽

Vol 747 ◽

pp. 448-455 ◽

Cited By ~ 1

Author(s):

Angela Coricciati ◽

Ilaria Ingrosso ◽

Antonio Paolo Sergi ◽

Alessandro Largo

Keyword(s):

Structural Health Monitoring ◽

Health Monitoring ◽

Optical Sensors ◽

Signal Transmission ◽

Weight Ratio ◽

Control Unit ◽

Fibre Bragg Grating ◽

Optical Fibres ◽

Structural Health ◽

Heritage Buildings

The preservation of heritage buildings requires multidisciplinary skills ranging from materials and seismic design up to structural monitoring.One of the most interesting innovative solution that is being developing in the last years is based on smart FRP (FRP – Fibre Reinforced Polymer) devices, which can combine contemporary reinforcing and monitoring purposes. The use of composite materials has many advantages in comparison with traditional retrofitting techniques, such as low weight, high strength-to-weight ratio, ease of handling, drapability, speed of installation, low thickness and visual impact. At the same time, monitoring the structure during its lifetime (strain, cracks, temperature, etc.) and evaluating its in-service integrity, in order to predict possible anomalous situations, can be achieved by the combination of FRP materials and embedded fibre optic sensors into a smart FRP device, suitable for both reinforcing and monitoring purposes. Optical fibres can provide reliable measurement even in harsh environment, as they are chemically durable, corrosion resistant, stable and insensitive to external electromagnetic and environmental perturbations, allowing long distances signal transmission and several measures in different points along the same optical fibre (multiplexing). Furthermore, the embedding into composite material will preserve them from rupture during handling and installation.In the present work, the application of smart FRP devices for the structural health monitoring of the Monastery in Sant’Angelo d’Ocre, L’Aquila, performed in the framework of the national project PROVACI, is reported.Six Smart Patches, consisting of FRP reinforcing sheet with point FBG (Fibre Bragg Grating) sensors embedded were applied on the extrados of two different vaults, while four Smart Rebars, consisting in FRP pultruded bars with distributed optical fibres sensors embedded, were installed in four buttress of one same vault. All the smart FRP devices, after being cabled, have been connected to the relative control units (BraggMETER from Fibersensing for FBG sensors and OBR4600 control unit of Luna Technologies for the distributed optical sensors) connected with a remote server for on-line remote monitoring.Before the installation, the Smart FRP devices have been preliminary calibrated and tested in the laboratory in terms of mechanical properties, strain sensitivity and accelerated aging.The monitoring on the Monastery has been conducted for five months, showing the reliability of entire system and of the signal transmitted by each sensor over the time.

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