Bridges Structural Health Monitoring and Deterioration Detection Synthesis of Knowledge and Technology

INE/AUTC 10.0

Review: optical fiber sensors for civil engineering applications

Optical fiber sensor (OFS) technologies have developed rapidly over the last few decades, and various types of OFS have found practical applications in the field of civil engineering. In this paper, which is resulting from the work of the RILEM technical committee “Optical fiber sensors for civil engineering applications”, different kinds of sensing techniques, including change of light intensity, interferometry, fiber Bragg grating, adsorption measurement and distributed sensing, are briefly reviewed to introduce the basic sensing principles. Then, the applications of OFS in highway structures, building structures, geotechnical structures, pipelines as well as cables monitoring are described, with focus on sensor design, installation technique and sensor performance. It is believed that the State-of-the-Art review is helpful to engineers considering the use of OFS in their projects, and can facilitate the wider application of OFS technologies in construction industry

Experimental Research on Corrosion-Induced Cracking Monitoring Based on Optical Fiber Sensor

Corrosion-induced cracking is a widely existent issue for coastal infrastructure, which leads to its advanced failure. The monitoring of corrosion-induced cracking is an important means of evaluating its influence on structure normal use and safe operation. However, traditional sensors such as strain gage are unsuitable to embed into concrete and to record long-term strain of concrete caused by steel bar corrosion. The optical fiber sensor, Brillouin Optical Time Domain Analysis (BOTDA) can effectively avoid the undetected phenomenon existing in point-wise test method, and it has the characteristic of automated monitoring. The optical fiber sensor is also electrical insulation and anti-electromagnetic interference; so it is suitable for detecting the corrosion-induced cracks. In this article, experimental research on corrosion-induced crack monitoring based on BOTDA is introduced. The distributed optical fiber is embedded into concrete around the steel bar to record expansion force of concrete. An accelerated corrosion test is performed to investigate the relationship between tiny geometrical changes of steel bar and concrete expansion force. Different rates of corrosion current are applied to the specimen. The accelerated corrosion test approved that the optical fiber sensor can effectively monitor the whole process of corrosion-induced cracking

Feasibility of Distributed Fiber Optic Sensor for Corrosion Monitoring of Steel Bars in Reinforced Concrete

This study investigates the feasibility of distributed fiber optic sensor for corrosion monitoring of steel bars embedded in concrete. Two sensor installation methods are compared: (1) attaching the sensor along the bar and (2) winding the sensor on the bar. For the second method, optical fibers were winded spirally on steel bars with different spacings: 0 mm, 2 mm, 5 mm, and 10 mm. Steel bar pull-out testing was conducted to evaluate the effect of presence of distributed sensor on the bond strength of steel—concrete interface. Electrochemical testing was carried out to assess the influence of the installation methods on the corrosion resistance of the reinforced concrete. Winding the optical fiber on steel bars with a 10-mm spacing does not affect the bond strength and corrosion resistance and allows real-time corrosion monitoring. The distributed sensor data can be used to estimate the corrosion induced steel loss and predict concrete cracking

Review on Strain Monitoring of Aircraft Using Optical Fibre Sensor

Structural health monitoring of aircraft assures safety, integrity and reduces cost-related concerns by reducing the number of times maintenance is required. Under aerodynamic loading, aircraft is subjected to strain, in turn causing damage and breakdown. This paper presents a review of experimental works, which focuses on monitoring strain of various parts of aircraft using optical fibre sensors. In addition, this paper presents a discussion and review on different types of optical fibre sensors used for structural health monitoring (SHM) of aircraft. However, the focus of this paper is on fibre bragg gratings (FBGs) for strain monitoring.  Here, FBGs are discussed in detail because they have proved to be most viable and assuring technology in this field. In most cases of strain monitoring, load conditioning and management employs finite element method (FEM). However, more effort is still required in finding the accurate positions in real time where the sensors can be placed in the structure and responds under complex deformation

Degradation Monitoring Systems for a BIM Maintenance Approach

Digitization allows to develop unprecedented technological systems based on the use of sensors, robotics, and automation. The construction industry is involved in this process of integrating new technologies through a platform called Building Information Modeling (BIM), which simplifies the management of the increasing complexity of construction processes. This methodology aims to create a global interactive system of information sharing between the different actors in the construction process. The integration of the processes creates economic and environmental opportunities, which can translate into increased efficiency of the sector. The information collected can be used throughout the construction lifecycle, which together with the monitoring of the buildings will support maintenance decisions. The monitoring of reinforced concrete structures with sensors allows the identification and quantification of the degradation processes, through the monitoring of several characteristic parameters of the reinforced concrete over time, and the determination of significant changes that indicate the existence of a degradative process in development. Obtaining this type of information, and its integration into BIM models, will allow intervention at an early stage in order to limit damages and costs associated with the maintenance of the structure, contributing to increase in the structure’s useful life

Towards Long-Term Monitoring of the Structural Health of Deep Rock Tunnels with Remote Sensing Techniques

Due to the substantial need to continuously ensure safe excavations and sustainable operation of deep engineering structures, structural health monitoring based on remote sensing techniques has become a prominent research topic in this field. Indeed, throughout their lifetime, deep tunnels are usually exposed to many complex situations which inevitably affect their structural health. Therefore, appropriate and effective monitoring systems are required to provide real-time information that can be used as a true basis for efficient and timely decision-making. Since sensors are at the heart of any monitoring system, their selection and conception for deep rock tunnels necessitates special attention. This work identifies and describes relevant structural health problems of deep rock tunnels and the applicability of sensors employed in monitoring systems, based on in-depth searches performed on pertinent research. The outcomes and challenges of monitoring are discussed as well. Results show that over time, deep rock tunnels suffer several typical structural diseases namely degradation of the excavation damaged areas, corrosion of rock bolts and cable bolts, cracks, fractures and strains in secondary lining, groundwater leaks in secondary lining, convergence deformation and damage provoked by the triggering of fires. Various types of remote sensors are deployed to monitor such diseases. For deep rock tunnels, it is suggested to adopt comprehensive monitoring systems with adaptive and robust sensors for their reliable and long-lasting performance

Implementation of an optical fiber sensor system to monitor the response of reinforced concrete due to formwork removal

Abstract : The movement of a section of a newly constructed reinforced 2-way suspended floor slab in the Department of Civil Engineering Science at the University of Johannesburg was monitored with an embedded optical fiber sensor (OFS) system during and after construction. The sensor system was used to monitor the strain in the structure before, during and after formwork removal. An OFS system was used due to its inherently distinct advantages such as its unobtrusiveness, lightweight and immunity to corrosion. This paper is concentrated on the findings of the results of these strain measurements with emphasis on the use of Fiber Bragg Gratings (FBG). Strain was measured over a 10 month period in a 5 m section of the suspended floor slab. Three periods during the 10 month period were observed. The first stage was showed 128 micro strain experienced by the structure. During the second stage the formwork was removed and large variations were monitored due to excessive external movement around the structure. The third stage indicated a 10 micro strain change. It was found that an OFS system can accurately measure the movement of reinforced concrete, thereby affording the design engineer to opportunity to monitor the structure during and after construction for large movements that can negatively affect the durability and the serviceability of the structure

Proceedings of Young Researchers' Forum II: Construction Materials

This is the second Young Researchers Forum for early-career scientists and engineers working in the field of construction materials to be held at Department of Civil, Environmental and Geomatic Engineering, University College London, London. The first meeting was organised by the Construction Materials Group, The Society of Chemical Industry in May 2012