Challenges and potential of fiber optic sensors for structural health monitoring of bridges: a review

Structural health monitoring (SHM) has gained significant attention in the field of civil engineering due to effective maintenance of structures, particularly bridges. However, traditional SHM methods have limitations in providing accurate and continuous data, which has led researchers to explore new technologies, one of which is fiber optic sensor (FOS) monitoring. This paper provides a comprehensivereview of the use of FOS in bridge SHM, highlighting the challenges and potential of this technology. FOS are convenient for SHM due to their high accuracy, immunity toelectromagnetic interference, and capability of working in harsh environments. They are particularly suitable for quasi-distributive anddistributive measurement systems on capital civil engineering structures. FOS can be utilized to measurevarious parameters, including deformation, temperature, and strain. In bridge constructions, FOS can beinstalled in multiple locations. Deformation measurements using FOS can provide accurate information on the displacement and deflection of the bridge, which can help in detecting abnormalities or damages. Temperature measurements using FOS can detect effects of thermal load on bridges, which can cause significant damage. Strain measurements using FOS can help describe the stress distribution in the bridge, which can be used for maintenance purposes. FOS-based SHM systems can provide real-time and continuous data, which can help in detecting any potential problems at an early stage and preventing catastrophic failures. The use of FOS in SHM of bridges has been extensively researched and demonstrated in various studies. However, challenges such as installation, calibration, and interpretation of the data require further research. The paper will discuss the potential of FOS-based SHM systems in improving the safety and reliability of bridge constructions. It will also highlight the challenges related to FOS installation, calibration, and data interpretation and provide insights into future research directions for developing more robust and cost-effective FOS-based SHM systems

Measurement of Prestressing Force in Pretensioned UHPC Deck Using a Fiber Optic FBG Sensor Embedded in a 7-Wire Strand

This paper presents the results of the performance test and long-term monitoring of the prestressing force inside concrete performed on a pretensioned Ultra-High Performance Concrete (UHPC) deck. The force is measured by applying a 7-wire strand embedded with an FBG (Fiber Bragg Grating) sensor. The performance test was conducted on a 3.7 m × 1.8 m pretensioned deck specimen through wheel loading tests to verify the applicability of the measurement method. In addition, a 12.3 m long and 4.8 m wide bridge with a pretensioned UHPC deck was erected and long-term monitoring was conducted over three years to verify the applicability of the method to real bridges. The effectiveness of the measurement method of the prestressing force inside concrete is verified, and the long-term monitoring data are used to investigate various temperature compensation methods. The results show that the proposed method enables effective measurement of small changes in the prestressing force inside the concrete. These changes are caused by the external forces acting on the bridge in service and provide sufficient durability for long-term sensing. The analysis of the prestressing force obtained through long-term monitoring reveals the necessity of conducting temperature compensation for the consistency of the data acquired using the FBG sensor. Moreover, the selection of the thermal expansion coefficient appears also to be of critical importance for temperature compensation

Использование оптического волокна G-652 для контроля горного массива угольных шахт

Introduction. The relevance of using fiber-optic sensors to monitor the geomechanical state of the mine workings of coal mines of the Karaganda coal-mining field is extremely high, because they are super-categorical and dangerous in a sudden explosion of coal dust and methane gas during mining operations in hazardous mines. Fiber optic sensors have several advantages: explosion safety, high accuracy, measurement speed and have good linearity of characteristics. Aim. The use of optical fiber of the ITU-T G.652.D standard as a sensor for monitoring the geomechanical state of an array of coal mines, which is very promising in terms of creating a distributed monitoring system capable of timely signaling to personnel about the danger of a sudden collapse of a mine. Materials and methods. To develop methods for monitoring and measuring the geotechnical parameters of the workings, a simulation laboratory bench based on fiber-optic sensors was developed. The authors used a quartz single-mode optical fiber 9/125 μm (OS2) Corning SMF-28e + ®. The article proposes systems in two variants, depending on the tasks and functionality. In the first variant, the well-known method of optical reflectometry OTDR (Optical time domain reflectometer) is used. In the second variant, the values of the additional losses caused by the mechanical action on the optical fiber are controlled. Results. During mechanical action on an optical fiber microcracks occur, leading to a change in the properties of light and an increase in additional losses of the light wave passing through it. Conclusion. The use of ITU-T G.652.D standard optical fiber for monitoring the geomechanical state of an array of coal mine workings is very promising, since the VODs developed on its basis have sufficiently high accuracy, measurement speed and good linearity of characteristics.Введение. Актуальность использования волоконно-оптических датчиков для контроля геомеханического состояния массива горных выработок угольных шахт Карагандинского угольного бассейна крайне высока, потому как они относятся к сверхкатегоричным и опасным по внезапному взрыву угольной пыли и газа метана при проведении горных работ в опасных условиях шахт. Волоконно-оптические датчики обладают рядом достоинств: взрывобезопасностью, высокой точностью, скоростью измерения и имеют хорошую линейность характеристик. Цель исследования. Использование оптического волокна стандарта ITU-T G.652.D как датчика для контроля геомеханического состояния массива горных выработок угольных шахт, что является весьма перспективным в плане создания распределенной системы мониторинга, способной своевременно сигнализировать персонал об опасности внезапного обрушения выработки. Материалы и методы. Для отработки методов контроля и измерения геотехнических параметров выработок был разработан имитационный лабораторный стенд на основе волоконно-оптических датчиков. Авторами использовалось кварцевое одномодовое оптическое волокно 9/125 мкм (OS2) Corning SMF-28e+®. В статье предложены системы в двух вариантах исполнения в зависимости от поставленных задач и функциональности. В первом варианте используется известный метод оптической рефлектометрии OTDR (Optical time domain reflectometer). Во втором варианте контролируются значения дополнительных потерь, вызванные механическим воздействием на оптическое волокно. Результаты. При механическом воздействии на оптическое волокно возникают микротрещины, приводящие к изменению свойств света и увеличению дополнительных потерь световой волны, проходящей по нему. Указанные потери можно измерить и установить значения давления на оптическое волокно, также можно определить величину смещения. Заключение. Использование оптического волокна стандарта ITU-T G.652.D для контроля геомеханического состояния массива горных выработок угольных шахт является весьма перспективным, так как разработанные на его основе волоконно-оптические датчики обладают достаточно высокой точностью, скоростью измерения и имеют хорошую линейность характеристик

Novel Approaches for Structural Health Monitoring

The thirty-plus years of progress in the field of structural health monitoring (SHM) have left a paramount impact on our everyday lives. Be it for the monitoring of fixed- and rotary-wing aircrafts, for the preservation of the cultural and architectural heritage, or for the predictive maintenance of long-span bridges or wind farms, SHM has shaped the framework of many engineering fields. Given the current state of quantitative and principled methodologies, it is nowadays possible to rapidly and consistently evaluate the structural safety of industrial machines, modern concrete buildings, historical masonry complexes, etc., to test their capability and to serve their intended purpose. However, old unsolved problematics as well as new challenges exist. Furthermore, unprecedented conditions, such as stricter safety requirements and ageing civil infrastructure, pose new challenges for confrontation. Therefore, this Special Issue gathers the main contributions of academics and practitioners in civil, aerospace, and mechanical engineering to provide a common ground for structural health monitoring in dealing with old and new aspects of this ever-growing research field

Comparing methods of controlling unauthorized access to fiber-optic transmission lines

In present day telecommunication systems the topical problem is protection of the subscribers' personal data against possible thefts and hacking fiber-optic information transmission guide lines, as this causes a number of dangerous situations and problems. The attackers, in spite of the legislative framework for the information protection, are still trying to read information from a fiber-optic transmission line (FOTL). This possibility arises due to incorrect installation and configuration of error protection, unauthorized access to information is possible. This article discusses two methods of detecting unauthorized admission (unauthorized access). The results of the study using an optical laser radiation source and power meter, as well as a YOKOGAWA optical reflectometer are presented. As a result, it was concluded that the method of preventing unauthorized access at the wavelength of 1625 nm can be used, since continuous FOTL monitoring will not interfere with the traffic

Application of surrogate modeling methods in simulation-based reliability and performance assessment of civil structures

Structures and infrastructure systems are subjected to various deterioration processes due to environmental or mechanical stressors. Proper performance assessment approaches capable of detecting potential structural damage and quantifying the probability associated with structural failure are required to formulate optimal maintenance and retrofit plans that minimize the risk of failure and maximize the safety of structures. However, due to the presence of several sources of uncertainty that can affect the performance assessment and decision-making processes (e.g., uncertainties associated with loading conditions and performance prediction models), applying probabilistic methods, such as Monte Carlo simulation, is essential. In this context, a large number of simulations is generally required to quantify the low failure probability associated with civil structures. Executing the required number of simulations may be computationally expensive, especially if complex and/or nonlinear structural models (e.g., finite element models) are involved. The use of surrogate modeling tools such as artificial neural networks, polynomial chaos expansion, and kriging can help in reducing the computational costs associated with simulation-based probabilistic analysis. The research proposed herein aims to develop probabilistic approaches for performance assessment and damage detection of structures using advanced simulation-based techniques coupled with surrogate modeling. The proposed methodology is applied to quantify the risk of bridge failure due to flood events considering the impact of climate change. The approach was extended to establish the time-variant flood fragility surfaces for bridges under flood conditions. This approach (a) integrates deep learning neural networks into a simulation-based probabilistic approach to predict the future river streamflow necessary for assessing the flood hazard at the bridge location and (b) simulates the structural behavior of the bridge foundation under sour conditions. In addition, the proposed methodology is used to quantify the reliability of bolted and welded steel connections by integrating finite element analysis and surrogate models. Low-rank tensor approximation and polynomial chaos kriging surrogate models are adopted to perform Monte Carlo simulation and quantify the reliability of the investigated combination connection. Finally, artificial neural networks were used to develop a statistical damage detection and localization approach capable of evaluating the performance of prestressed concrete bridge girders using fiber optic sensors

Fiber Bragg Grating Based Sensors and Systems

This book is a collection of papers that originated as a Special Issue, focused on some recent advances related to fiber Bragg grating-based sensors and systems. Conventionally, this book can be divided into three parts: intelligent systems, new types of sensors, and original interrogators. The intelligent systems presented include evaluation of strain transition properties between cast-in FBGs and cast aluminum during uniaxial straining, multi-point strain measurements on a containment vessel, damage detection methods based on long-gauge FBG for highway bridges, evaluation of a coupled sequential approach for rotorcraft landing simulation, wearable hand modules and real-time tracking algorithms for measuring finger joint angles of different hand sizes, and glaze icing detection of 110 kV composite insulators. New types of sensors are reflected in multi-addressed fiber Bragg structures for microwave–photonic sensor systems, its applications in load-sensing wheel hub bearings, and more complex influence in problems of generation of vortex optical beams based on chiral fiber-optic periodic structures. Original interrogators include research in optical designs with curved detectors for FBG interrogation monitors; demonstration of a filterless, multi-point, and temperature-independent FBG dynamical demodulator using pulse-width modulation; and dual wavelength differential detection of FBG sensors with a pulsed DFB laser

Testing of Materials and Elements in Civil Engineering

This book was proposed and organized as a means to present recent developments in the field of testing of materials and elements in civil engineering. For this reason, the articles highlighted in this editorial relate to different aspects of testing of different materials and elements in civil engineering, from building materials to building structures. The current trend in the development of testing of materials and elements in civil engineering is mainly concerned with the detection of flaws and defects in concrete elements and structures, and acoustic methods predominate in this field. As in medicine, the trend is towards designing test equipment that allows one to obtain a picture of the inside of the tested element and materials. Interesting results with significance for building practices were obtained