Kapitel

• FrontmatterWerner, Lienhart; Markus, Krüger; 10.3217/978-3-99161-057-1-000
• Digitalizing Infrastructure: Advancing Structural Health Monitoring for Smarter Asset ManagementKeßler, Sylvia; 10.3217/978-3-99161-057-1-001
• SHM for bridges – the work flowSodeikat, Christian; 10.3217/978-3-99161-057-1-002
• Bridge in service structural monitoring: the SCSHM benchmarkLimongelli, Maria Pina; 10.3217/978-3-99161-057-1-003
• Distributed fiber optic sensing in civil structural health monitoring at the next level – Realization of a comprehensive sensing network along the Brenner Base TunnelMonsberger, Christoph M.; Buchmayer, Fabian; Winkler, Madeleine; Cordes, Tobias; 10.3217/978-3-99161-057-1-004The Brenner Base Tunnel (BBT) is one of the key infrastructure projects currently under construction and will be one of the longest underground railway connection with a total length of approximately 64 km once completed. Its service life of 200 years implies essential requirements on the tunnel design. One important focus is to increase the availability of the tunnel, e.g. by enabling optimized maintenance work based on appropriate monitoring. The tunnel owner BBT SE has therefore initiated an enhanced Distributed Fiber Optic Sensing (DFOS) network inside the segmental lining for structural health monitoring without human access. The technology has significantly evolved in recent years to monitor large scale infrastructure, especially for in-situ tunnel monitoring as the distributed sensing feature can provide a complete picture of the strain distribution without blind spots. This contribution introduces the designed DFOS network, consisting of more than 35 km sensing cable along numerous tunnel cross-sections, spread over more than 30 km tunnel drive and two different construction lots. The monitoring data is autonomously evaluated and transferred to the online dashboard in real time. Analysis of the strain distribution provides fundamental information about the actual loading state of the segmental lining. The results together with experiences gained from practical implementations demonstrate the technology’s high potential for innovative civil structural health monitoring.
• Stevenson Creek Experimental Dam Monitoring Centenary: Overview and Perspectives of Strain Sensing and Strain-Based Monitoring of Civil StructuresGlisic, Branco; 10.3217/978-3-99161-057-1-005
• The Power of Optical and SAR Imaging for Remote Monitoring of Land and InfrastructureMazzanti, Paolo; 10.3217/978-3-99161-057-1-006
• Monitoring of fatigue crack propagation by means of distributed fiber optic sensingDohnalík, Petr; Lachinger, Stefan; Kwapisz, Maciej; Vorwagner, Alois; 10.3217/978-3-99161-057-1-007Distributed Fiber Optic Sensing (DFOS) is an innovative technique for Structural Health Monitoring (SHM). Taking advantage of the fact that DFOS can conveniently measure mechanical strain continuously along an optical fiber, it is increasingly used in monitoring of concrete bridges and tunnels. However, DFOS still needs research in new application areas, such as monitoring of steel bridges. In the present study, DFOS is used to investigate the potential to monitor fatigue crack initiation and propagation by experiments. In a full-scale test, a steel railway bridge was dynamically excited into resonance, generating fatigue-effective vibration amplitudes. The fiber was glued to the flange of the main beam in several loops to cover a larger area for crack detection. The measured strain signal was compared with results obtained from Finite Element Method (FEM) simulations supported by data acquired from conventional strain gauges and extensometers. The strain measurement with DFOS showed excellent agreement with the simulated strain. In this context, additional information about crack initiation, propagation, opening and length can be obtained indirectly from the DFOS measurement. However, when the crack is crossing the fiber, nonlinear effects come into play. To consider the nonlinear effects, a hysteresis model taking steel-fiber interaction into account was applied. The results of the study are presented and the applicability and potential of DFOS for fatigue crack monitoring in railway bridges is discussed.
• Updating prediction of fatigue reliability index of railway bridges using structural monitoring data and updated load historiesRalbovsky, Marian; Lachinger, Stefan; 10.3217/978-3-99161-057-1-008The assessment of fatigue consumption and the remaining lifetime of structural components is affected by considerable uncertainties on the side of the traffic loads, fatigue resistance and structural response. The purpose of the presented work was to develop methods for dealing with these uncertainties, as well as methods for improving the accuracy of assessment with the use of additional data. Within the research project Assets4Rail, a structural monitoring system was installed on a railway bridge located on a local track in Austria. The system consisted of strain sensors, acceleration sensors and inclinometers. It was used to measure the bridge response during train passages with known axle loads in course of a test with controlled conditions. This data was used to calibrate the structural model and develop probabilistic methods for fatigue assessment. Influence lines at fatigue-critical locations were evaluated from measured bridge strain response including their uncertainty. Further uncertainties considered in the assessment include the load histories and the fatigue resistance. The results showed the largest contribution by evaluation of model uncertainties from monitoring data. The effect of model updating was also considerable, but less significant. Further increase of estimation accuracy is achieved using section-specific traffic data. Whereas wayside monitoring data represent the reference scenario, the use of traffic management data provides a usable alternative.
• Monitoring of wind induced vibration on a tied-arch railway bridge.Castillo Ruano, Pablo; Martinez, Cesar; Dallinger, Sonja; 10.3217/978-3-99161-057-1-009The ÖBB Rheinbrücke, situated in the vicinity of Lustenau, represents a novel approach to steel-concrete composite arch structure engineering, boasting a span of 102 meters. The primary supporting structure is a tied-arch comprising 12 round steel hangers, each with a diameter of 100 mm, situated on either side of the bridge. The maximum length of the hangers is 18.9 meters. In arch bridges of this type with steel hangers, wind-induced vibrations in the hangers can result in high-frequency, high-amplitude fluctuations in stress levels, particularly in the hangers and their connections. This can be problematic from the perspective of fatigue, particularly given that the hanger connections often have notch-sensitive details. Following the completion of the bridge, comprehensive monitoring was conducted in accordance with the original plan. This was done with the objective of acquiring data regarding the vibrations experienced by the hangers and the subsequent damage to the material. This data was then used to determine whether vibration-reducing measures were necessary. During the course of monitoring and subsequent evaluation, it was observed that wind-induced vibrations in the hangers could result in the occurrence of fatigue-relevant stress ranges. This article serves to emphasise the importance of structural health monitoring in confirming the efficacy of vibration reduction measures, which have the potential to extend the service life of railway bridges.
• Acoustic emission monitoring of fatigue cracks for railway steel bridge inspectionProkofyev, Mikhail; Marihart, Heribert; Lackner, Gerald; 10.3217/978-3-99161-057-1-010Railway steel bridges are often affected by material fatigue, i.e. crack formation and crack growth at areas of high stress concentrations under millions of load cycles due to the traffic load. To support the continued safe operation of these structures a flexible and robust system solution for structural health monitoring is needed. It provides the responsible bridge inspector with useful information regarding the current condition and the future development of the monitored area. This offers the infrastructure operator an opportunity for optimised planning of inspection intervals and maintenance measures and helps to extend the service life of these structures. For this purpose, the RISE system was developed by TÜV AUSTRIA in close cooperation with the Austrian Federal Railways ÖBB. The RISE system monitors fatigue cracks and/or highly stressed areas using acoustic emission (AE). The system records the AE response from the monitored area while the material is stressed by the usual day-to-day railway operations. The analysis of the change of this material response over the monitoring period is used to predict the future development of the crack. In this paper the application of the RISE system for bridge inspection is presented for steel bridges in the railway network of ÖBB. The system solution is presented as a whole, from the installation on-site until the evaluation of the monitoring data and the obtained results supporting the responsible bridge inspectors.
• Rail track subsurface imaging from train vibrations recorded at dark fiber networksBehm, Michael; Brauner, Michael; 10.3217/978-3-99161-057-1-011We demonstrate the practical feasibility of assessing geotechnical parameters of rail infrastructure based on ‘dark fiber’ distributed acoustic sensing (DAS) recordings using trains as sources. A workflow to image the shallow (3 m – 20 m depth) subsurface in terms of shear wave velocity has been established. The shear wave velocity distribution is obtained from inversion of seismic surface waves excited by the trains and recorded on the fiber optic cables, and is used as a proxy for the geotechnical strength (e.g., shear modulus). Our results allow for the interpretation of potential geologic hazards and other features relevant for assessing the geotechnical integrity of rail infrastructure. This approach does not require dedicated field measurements or interruption of the train schedule, and therefore represents a cost-effective and robust method for different application scenarios.
• Monitoring of Concrete Infrastructure with Active Ultrasound Coda Wave InterferometryEpple, Niklas; Sanchez Trujillo, Camila; Fontoura Barroso, Daniel; Hau, Julia; Niederleithinger, Ernst; 10.3217/978-3-99161-057-1-012Coda Wave Interferometry has been used in Geophysics to detect weak changes in scattering media. Past research in Structural Health Monitoring has shown that this methodology can be applied to concrete structures to detect material changes by calculation of relative velocity changes. Successive measurements with embedded ultrasonic transducers provide a repeatable signal for reliable long-term monitoring of concrete. To research the application in real-world structures, we have embedded ultrasonic transducers in a bridge in Ulm and a Metro station in Munich, Germany. This study gives an overview of the monitoring of these two structures. The results show the potential and challenges of the method. Data evaluation can be largely automated to gain insights into material changes and other influences on the structure, such as traffic-induced load and temperature variations. The experiments demonstrate the ease of installation, longevity of the sensor installation, and sensitivity of the measurement technique, but highlight problems with the application, especially if electromagnetic noise affects data quality. As no confirmed substantial damage was recorded during the monitoring period on both structures, we evaluate load tests to investigate the effect of static load on the structures and the coda monitoring results. The experiments show that the influence of load can be detected, even if the temperature influence is not removed from the data. This indicates that online damage detection with coda monitoring is possible, but further research on damage detection in real-world structures has to be conducted to confirm laboratory findings.
• Finite element mesh construction for seismic analysis using drone imageryDelaney, Evan; Marty, Patrick; Gebraad, Lars; Zunino, Andrea; Fichtner, Andreas; 10.3217/978-3-99161-057-1-013Computational meshes serving as input to wave simulations are often crafted manually and bear a significant cost to construct. The aim of this work is to minimize that overhead and apply it to structures lacking models and meshes, particularly in earthquake-prone regions, to image and monitor their structural health in response to ground movement. To address this challenge, we have developed a workflow to facilitate the creation of 3D finite element meshes, starting with 2D photos acquired by an inexpensive consumer-level unmanned aerial system (i.e., a drone). After photo acquisition, the process proceeds by utilizing computer graphics and vision software to transform these photos into a 3D surface composed of triangles. Surface meshes are generally sufficient products for other workflows that likewise create 3D assets via reconstruction methods (e.g., for topographic mapping, archiving, and entertainment). However, to simulate waves through complex structures with high fidelity, we employ a spectral element wave solver, which requires a 3D volume composed of hexahedra. The steps from a 3D triangular surface to a 3D hexahedral volume include enclosing the surface, conditioning, and remeshing it with appropriate element geometry. We apply a first version of this workflow to the Contra (Verzasca) dam in Switzerland, from which we discuss key stages, challenges, and learnings in developing the pipeline – showcasing elastic wave simulation through the constructed mesh.
• A review of methods and challenges for monitoring of differential settlement in railway transition zonesNasrollahi, Kourosh; Nielsen, Jens; Dijkstra, Jelke; 10.3217/978-3-99161-057-1-014Differential settlement in ballasted railway tracks, particularly in transition zones between two track forms, poses a critical challenge for railway infrastructure. Such settlement, often exacerbated by a stiffness gradient due to changes in track superstructure and substructure, typically causes a local dip in the longitudinal track level a few metres from the transition, leading to higher dynamic traffic loading and reduced passenger comfort. Regular monitoring of transition zones is essential for safe operations and cost-effective maintenance. This paper reviews methods for monitoring differential settlement in railway tracks. To measure the properties and loading of the superstructure, potential methods include fibre Bragg grating (FBG) sensors, point receptance measurements, track geometry (and track stiffness) recording cars, and wheel load impact detectors (WILD). Characterisation of the subgrade can be carried out via a multichannel analysis of surface waves (MASW), dynamic cone penetration tests (CPT), interferometric synthetic aperture radar (InSAR), frost sticks for temperature monitoring, and total stations. Lessons learned from an in-situ measurement involving an extensive FBG-based system deployed in northern Sweden to monitor a transition zone in harsh weather conditions are presented. Integrating a combination of monitoring methods with a simulation model to verify and support the accurate prediction of differential settlement is a useful approach to addressing challenges associated with track stiffness gradients and guiding the improvement of transition zone designs.
• Advanced Structural Health Monitoring and Predictive Maintenance of the Parchi Viaduct Using Distributed Fiber Optic Sensors and Digital Twin TechnologyWeissenbach, Nils; Penasa, Massimo; 10.3217/978-3-99161-057-1-015Aging infrastructure poses significant challenges in ensuring safety, reliability, and long-term serviceability. The Parchi Viaduct, a 3-km multi-span structure on Milan’s A51 Eastern Ring Road, experienced critical degradation in its Gerber saddles, necessitating temporary closure for safety assessments. In response, Milano Serravalle Milano Tangenziali S.p.A. and CAEmate S.R.L. deployed an advanced Structural Health Monitoring (SHM) system, integrating distributed fiber optic sensing (DOFS) and a physics-informed digital twin (PINN) to enable real-time load-bearing capacity evaluation and predictive maintenance. This paper presents the implementation of the WeStatiX SHM platform, utilizing DOFS to capture strain, temperature, and vibration data while dynamically updating a finite element model (FEM) through inverse analysis and multi-objective optimization. By continuously refining modal parameters such as natural frequencies, mode shapes, and damping ratios, the system enables early detection of structural anomalies and degradation trends. The validated digital twin successfully predicted real-world structural behavior, confirming residual load-bearing capacity despite saddle deterioration and supporting the safe reopening of the viaduct under real-time monitoring per Italian NTC standards. Load test results and FEM simulations demonstrated excellent agreement, with taller piers exhibiting ~20% greater deflection, emphasizing pier height's impact on load distribution and deformation patterns. These findings enhance predictive maintenance planning, improve stress redistribution modeling, and contribute to prolonging the structural lifespan of aging infrastructure assets.
• A digital twin based integrated sustainability and quality assurance concept for subway constructionsGrosse, Christian U.; Wurzer, Otto; 10.3217/978-3-99161-057-1-016In regard to subway structures, non-destructive testing and structural health monitoring techniques are beneficial for construction and operation, which require an integrated quality control and sustainability concept. Such an integrated concept is presented, focusing on two main tasks. Inspection during construction will lead to a better quality of the components and structures. Proper data can be integrated into a building information model (BIM). The conceptual design should, however, anticipate later impacts and possible deteriorations at critical parts. The building information model could then be continued (updated) in the form of structural health monitoring (SHM) to make (visual) maintenance of subway structures more efficient, resulting in fewer disruptions (fewer closures, less downtime) and lower costs. It can also contain sensors at non-visible or non-assessible locations. Recording impacts on the structure (e.g. loads, vibrations, chlorides) enables a digital model as a so-called digital twin and the calculation of the remaining service life. Such a concept is presented for a new subway station in Munich.
• Evolving reliability-based condition indicators for structural health monitoring into a digital twin of a cable-stayed bridgeHerbrand, Martin; Wenner, Marc; Lazoglu, Alex; Ullerich, Christof; Zehetmaier, Gerhard; Marx, Steffen; 10.3217/978-3-99161-057-1-017In Germany, the bad condition of many older bridges and changes in the code provisions often result in deficits after assessment and recalculation. In case the necessary structural safety is not provided, structural health monitoring can be employed to gain knowledge about the time variant actions, the progression of structural damage and the overall condition of structures. To allow for effective use of the usually dense monitoring raw data, the derivation of condition indicators is key, since they indicate a need for action for the owners and the engineers. At the same time, real-time data as well as comprehensive condition indicators are key elements for creating a Digital Twin of a structure, as a Digital Twin requires a bidirectional flow of data, which affects the physical entity of the twin. In this paper, a method for deriving condition indicators from monitoring data is described which was developed for a large cable-stayed bridge, the Köhlbrand Bridge in Hamburg, Germany. The method allows for the calculation of a reliability index as a time variant condition indicator based on dynamic monitoring data, which is then implemented into a Digital Twin of the structure.
• Advancements in Distributed Fiber-Optic Sensing: Comparing Brillouin and Rayleigh Technologies for Geotechnical and Structural MonitoringNöther, Nils; Facchini, Massimo; Aguilar-López, Juan Pablo; 10.3217/978-3-99161-057-1-018We report on recent developments in distributed fiber-optic strain and temperature sensing (DTSS) technologies. In recent years, both Brillouin- and Rayleigh-based fiber-optic sensing systems have found an increasing number of applications measuring static and dynamic displacement and deformation events in geotechnical and structural health monitoring. The focus of this contribution is on Brillouin-based DTSS systems, for which we present recent advancements in spatial resolution and signal-to-noise ratio under harsh real-world conditions. The state-of-the-art Brillouin DTSS technology is considered also in relation to Rayleigh-based technologies like c-OFDR and DAS systems that also play an increasing role in geotechnical and structural monitoring, in order to illuminate the technology-specific strengths and challenges within the DFOS family. Recent insights from industrial projects and research activities in embankment monitoring are presented.
• Hybrid monitoring systems: synergising distributed fibre optic sensing with spot measurementsSieńko, Rafał; Howiacki, Tomasz; Bednarski, Łukasz; Zuziak, Katarzyna; 10.3217/978-3-99161-057-1-019The diagnosis and maintenance of both new and ageing infrastructure are among the main challenges facing the civil engineering and geotechnical industries today. The effectiveness of monitoring systems depends on several factors, including the choice of measurement techniques. Conventional point-based methods (e.g., vibrating wire sensors, electrical strain gauges, or accelerometers) are inherently limited by their locality, as they cannot directly capture what occurs between discrete measurement points. In contrast, distributed fibre optic sensing (DFOS) introduces new capabilities for structural condition assessment by enabling continuous measurement of various physical quantities along the entire length of the sensor. This eliminates the risk of missing localized extreme events or damages, such as cracks, leakages, or stress concentrations. However, the widespread adoption of DFOS is hindered by the high costs of optical interrogators, which often restrict its use to periodic measurements rather than fully automated monitoring. A practical solution to this challenge is the synergistic combination of point-based and distributed technologies within hybrid monitoring systems. Such systems leverage the strengths of both approaches, offering a more comprehensive understanding of structural behavior. This paper explores the concept of hybrid systems, illustrating their potential and real-world applications through selected case studies.
• Water distribution pipeline anomaly detection using distributed acoustic sensing (DAS)Jasiak, Maksymilian; Chiu, Shih-Hung; Saw, Jaewon; Hubbard, Peter; Katzev, David; Soga, Kenichi; 10.3217/978-3-99161-057-1-020Leak detection for water pipelines, and anomaly detection more broadly, is vital to ensuring reliable access to drinking water. Monitoring transmission and distribution pipelines supports proactive fault detection to reduce water loss amid deteriorating infrastructure and depleting water resources. Distributed acoustic sensing (DAS) in the form of phase-sensitive optical time-domain reflectometry (φ-OTDR) can quantify vibrations and sound along fiber optic cables over long distances with high spatial resolution and frequency. In this study, DAS was deployed on a new fiber optic cable-instrumented pipeline to investigate DAS sensitivity to pipe water leakage noise. A reproducible workflow for system deployment and signal processing aimed at pipe water leak detection in field conditions is presented. The influence of fiber optic cable type (tight-buffered vs. loose tube) and installation condition (pipe-mounted vs. trench-lain) on DAS sensitivity was assessed during pipe water filling and simulated leakage. Findings demonstrate relatively high sensitivity to water leak noise detection when DAS is deployed on fiber optic cables near the pipeline. This informs best practices for data-driven pipeline monitoring by presenting a reproducible procedure to operationalize water pipeline leak detection using DAS.
• Integrating Distributed Acoustic Sensing for Damage Detection in Old Pre-Stressed Concrete Girders: Preliminary Experimental ResultsStrasser, Lisa; Lienhart, Werner; Moser, Thomas; Anžlin, Andrej; Kosič, Mirko; Kreslin, Maja; Hekič, Doron; 10.3217/978-3-99161-057-1-021In this study, we investigate the load-bearing capacity of pre-stressed concrete girders under various damage levels. We employed Distributed Acoustic Sensing (DAS) technology to monitor and quantify changes in the girder response as damage levels were incrementally introduced. This approach enabled the real-time measurement of dynamic behavior over the entire length of the girder, allowing for a detailed characterization of damage-induced structural changes. To complement the DAS-based approach, we also applied classical acceleration-based damage detection techniques. By integrating these methods, we aimed to cross-validate the results and provide a more comprehensive understanding of damage progression and its impact on structural performance. The experimental campaign, conducted in Ljubljana, ZAG, involved full-scale testing of pre-stressed concrete girders subjected to controlled damage scenarios. This setup ensured a realistic assessment of the girders’ residual capacity and failure mechanisms. The paper presents preliminary results from this experimental study, emphasizing the capability of DAS measurements to detect and characterize damage, while also comparing its performance against traditional methods. By combining advanced sensing technologies with established techniques, this research highlights the potential of DAS as a transformative tool in structural health monitoring.
• Structural performance monitoring for concrete girder bridges with distributed fiber optic sensorsFabbricatore, Francesco; Bertola, Numa; 10.3217/978-3-99161-057-1-022The alarming frequency of bridge collapses in recent years underscores the critical need for advanced monitoring strategies tailored to existing infrastructure. Many concrete bridges, built decades ago, now face increasing traffic demands and environmental stressors that threaten their structural integrity. This study investigates the use of distributed fiber optic sensors (DFOSs) with high spatial resolution (independent strain measurements every 2.6 mm) during static load tests to assess the structural performance of concrete girder bridges. The goal is to gain a deeper understanding of their condition using data-driven approaches. The fiber optic technology provides detailed strain profile information that gives insights into global bridge behavior, such as stress distributions, support conditions and static responses. It also allows the detection of cracks along the fiber path and other localized effects that may remain undetected without a calibrated numerical model. This method of structural performance monitoring is applied to a prestressed concrete bridge in Switzerland. Static load tests have been performed on a full-scale bridge in Switzerland and the resulting distributed strain datasets allow the accurate understanding of bridge behavior, including deflection extrapolation and crack detection. The results underline the potential of DFOS to develop novel data-driven solutions for extending the service life of structures.
• AI-driven Smart-Liner System with DFOS for Digital Twin-Based Real-Time Monitoring of Oil and Gas InfrastructureDuan, Junyi; Wang, Xingyu; Yan, Huaixiao; Wang, Sike; Huang, Ying; Tao, Chengcheng; 10.3217/978-3-99161-057-1-023This study presents an innovative AI-powered smart-liner system designed to enhance the safety and efficiency of oil and gas transportation and storage infrastructure. By integrating polymer composite liners with distributed fiber optic sensors (DFOS), the system enables continuous monitoring of mechanical deformations and damage formation, providing real-time insights into the infrastructure’s condition throughout its lifespan. Finite element analysis (FEA) is employed to simulate the mechanical responses of the smart-liner-protected specimen over time. Machine learning (ML) algorithms are applied to analyze images generated from collected DFOS data, enabling the identification and assessment of risk variations across different locations and time steps. This approach demonstrates the high accuracy and effectiveness of ML in automatically detecting deformations and crack formation under buckling loading conditions. The methods enable comprehensive structural health monitoring, allowing for precise localization, visualization, and quantification of mechanical changes and damage within the infrastructure. With the above approaches, the smart-liner system facilitates continuous data collection across the entire protected surface, supporting the development of a dynamic digital twin model that evolves alongside the infrastructure. The findings provide critical insights for the oil and gas industry, offering an advanced and efficient solution for monitoring and mitigating risks associated with transportation and storage infrastructure.
• Middle range, rapid strain sensing based on PNC-OFDR and its application to bridge monitoringYoshimura, Yuichi; Fujiwara, Kotaro; Taira, Yohei; Imai, Michio; Zhang, Chao; Ito, Fumihiko; 10.3217/978-3-99161-057-1-024Distributed fiber optic sensing is a suitable method for long-term, wide-area monitoring of civil engineering structures such as the ground, tunnels, dams, and bridges. In recent years, distributed strain sensing technologies such as distributed acoustic sensing (DAS) and optical frequency domain reflectometry (OFDR), which can realize real-time monitoring, have made remarkable progress. In particular, OFDR, which performs strain sensing with high spatial resolution, can quantitatively evaluate the strain distribution of civil engineering structures with an accuracy comparable to conventional strain gauges. This method has been limited in its application to structural health monitoring due to its short measurement range. However, by extending the sensing distance, it is evolving into a practical technology for on-site testing. This paper introduces middle-range, rapid strain sensing based on Phase-noise-compensated OFDR (PNC-OFDR) and its application to bridge monitoring. Optical fiber sensors were installed on bridge girders, and the change in strain distribution when the moving load was applied by vehicles was measured using the PNC-OFDR sensing system.
• Advanced Structural Monitoring and Predictive Maintenance for Railway Bridges Using Distributed Fiber-Optic SensorsMunoz, Felipe; Eguidazu, Iván; Rodriguez, Julio; Gaston-Beraza, Diego; Basarte, Fernando; Urricelqui, Javier; Perez-Casas, José María; Jimenez-Rodriguez, Marco; 10.3217/978-3-99161-057-1-025This submission presents a structural monitoring solution for railway bridges and viaducts that leverages distributed fibre optic sensors (distributed temperature and strain sensing, DTSS, and distributed acoustic sensing, DAS) to capture both long-term static trends and dynamic behaviour under train loads. The long-term monitoring uses hourly DTSS strain measurements, accounting for day/night and seasonal variations, while the dynamic monitoring system records real-time strain and vibration data during train passages. By integrating these measurements with structural calculation services, the system can detect anomalies (e.g., stiffness changes, potential cracking) and inform predictive maintenance. Lastly, the results are displayed via a digital twin, providing an intuitive, web-based platform for analysing historical data and forecasting future conditions.
• Structural health monitoring in underground mining using fiber-optic sensing and 3D laser scanning for digital twin developmentMartin, Michael Dieter; Nöther, Nils; Paffenholz, Jens-André; 10.3217/978-3-99161-057-1-026This study aims to evaluate the use of distributed fiber-optic strain and temperature sensing for structural health monitoring in underground mining drifts and chambers including 3D mobile laser scanning. This method seeks to create a digital twin to improve safety and efficiency through better digital planning. Temperature and deformation data from distributed fiber-optic sensing (DFOS) cables will serve as boundary conditions of the combined ventilation and geomechanical models of the drift and chambers. Initially, a 60-meter-long drift will be monitored using fiber-optic cables. Next, deformations of a flexible arch support, induced by hydraulic cylinders, will be observed. A hydraulic cylinder will then apply load orthogonally to the rock. Fiber-optic cables will be inserted and cemented into the rock, along rock bolts, and in boreholes around each bolt to measure deformations from rock bolt pull-out tests. Preliminary examinations identified the best adhesive bonding method for DFOS cables, considering the specific ambient conditions. A 3D point cloud will be used to plan and validate the cable installation. The meshed 3D cloud will serve as the foundation for the combined ventilation and geomechanical models, creating a virtual reality-capable digital twin enhanced with live DFOS measurements.
• Fibradike sensor: validation through full-scale field testingHöttges, Alessio; Rabaiotti, Carlo; Rosso, Alessandro; 10.3217/978-3-99161-057-1-027Earthen geohydraulic structures, such as dams and river embankments, are vital for water resource management and flood control, especially as climate change and urbanization increase hydrological risks. Internal erosion, often triggered by seepage, remains a major failure mechanism and can cause sudden, catastrophic collapses. Traditional monitoring systems lack the spatial and temporal resolution needed for effective early detection. To address this gap, a novel Distributed Pressure Sensor (DPS) based on distributed fiber optic (DFO) technology has been developed by the University of Applied Sciences of Eastern Switzerland (OST). The DPS offers high spatial resolution and extended range, enabling precise measurement of distributed pore water pressure - key for early detection of internal erosion processes. Following successful laboratory validation, the DPS was deployed in a full-scale test embankment (84 m long, 39 m wide, 4 m high) at the AIPo Research and Technical Centre in Boretto, Italy. Preliminary results show that the DPS accurately captured pore pressure evolution, matching conventional piezometer readings while detecting localized variations and two-dimensional flow effects that point sensors could not resolve. These findings highlight the DPS system’s strong potential for improving early warning capabilities in geohydraulic structure monitoring.
• Identification and quantification of concrete cracks using various distributed fiber optic sensing techniquesMonsberger, Christoph M.; Winkler, Madeleine; Kornberger, Anna Theresa; Schlicke, Dirk; 10.3217/978-3-99161-057-1-028Distributed fiber optic sensors (DFOS) are extensively used for concrete crack monitoring in recent years, especially in scientific-related applications and laboratory testing. These mainly focus on Rayleigh scattering due to its high spatial resolution and strain resolution, but with significant limitations in the sensing range. This contribution introduces an enhanced laboratory test series, in which five individual test specimens were equipped with multiple installation setups and tested under well-known conditions. The sensing network was interrogated using four different sensing units based on high-resolution Rayleigh as well as Brillouin scattering. The resulting strain sensing profiles do not only allow an identification of the crack location itself, but also a quantification of the crack width. It can be demonstrated that Brillouin sensors are definitely capable of capturing reliable crack widths over long distances, despite their limitation in the spatial resolution. The outcomes are significantly important in practice as civil infrastructures often require monitoring over several kilometers.
• DFOS-Based Monitoring of Prestressed Concrete Bridge GirdersLila, Kleo; Herbers, Max; Richter, Bertram; Agreiter, Andrea; Kreslin, Maja; Triller, Petra; Anžlin, Andrej; Lienhart, Werner; Marx, Steffen; 10.3217/978-3-99161-057-1-029Due to bridges’ critical role in transportation networks, the assessment and maintenance of existing bridges have become a priority. Prestressed concrete bridges constitute a significant portion of Europe’s transportation network, yet many no longer meet today’s technical requirements. This is primarily due to two factors: (i) the unforeseen increase in heavy goods traffic, and (ii) insufficient experience with early reinforced and prestressed concrete construction methods, coupled with inadequate regulations, which resulted in design weaknesses and structural deficiencies. One critical failure mechanism, identified when recalculating existing bridges based on updated guidelines, is insufficient shear load-bearing capacity, which has prompted the premature demolition of numerous bridges. A thorough understanding and rigorous monitoring of shear behavior is essential since neglecting this problem could lead to notable consequences, especially for aging infrastructure. In this paper, a distributed fiber optic sensor (DFOS) based monitoring system, inspired by shear detection concepts, is tested. A decommissioned prestressed concrete bridge girder was equipped with a DFOS grid, allowing for detailed monitoring of crack width, location, and shape. Preliminary test results confirm the successful installation and early detection of cracks, highlighting the system’s potential to identify microcrack formation, monitor crack growth, and support maintenance strategies.
• Proposed approach for direct rail state monitoring with distributed acoustic sensing DASDługosz, Szymon; Howiacki, Tomasz; Sieńko, Rafał; Bednarski, Łukasz; 10.3217/978-3-99161-057-1-030Railways are one of the fundamental modes of transportation, dating back centuries. They allow for the movement of people and goods across hundreds and thousands of kilometres. Such a large system relies on precise timing and excellent organization. Any incident or failure can result in losses amounting to millions of euros and cause unacceptable delays. Monitoring the condition of the railway is necessary to ensure safety and system effectiveness, but it is challenging due to the long distances that need to be monitored. Conventional sensors can provide high-quality data, but they do not offer a complete picture of the railway’s state, and local defects can be overlooked. A great solution for railway monitoring is DAS. A fibre optic sensor integrated with the structure can be used to obtain information about strain and vibration, with a fine resolution of even down to 1 metre, over tens of kilometres of track. Installing the sensor in the railway substructures can be challenging and exposes the sensor to potential damage. Another approach discussed in the article is to attach the sensor directly to the rail. Long sections of track can be covered with monitoring within a few hours using automated machine, enabling direct measurement of the rail’s condition. This paper presents the results of such installation, showing the potential of synergizing monolithic distributed fibre optic sensors with DAS technology to increase the safety and reliability of rail transport.
• Monitoring Timber Structures with Fiber Optics Sensors: State of the Art and Application to a Timber BeamMansilla-Ruiz, Roberto; Paya-Zaforteza, Ignacio; Garcia-Castillo, Ester; Calderon, Pedro A.; 10.3217/978-3-99161-057-1-031Fiber optic sensors (FOS) offer compelling advantages for Structural Health Monitoring (SHM). However, their application in timber structures remains underexplored. This article reviews the state-of-the-art use of FOS in timber structures and presents an experimental study conducted at the Universitat Politècnica de València. A 3-meter-span timber beam was subjected to a four-point bending test and instrumented with long-gauge strain FOS. The measured strains were used to derive stresses, which were then compared to theoretical values. The results highlight the potential of FOS for accurate stress monitoring in timber elements and contribute valuable insights to the advancement of SHM in sustainable construction.
• Pi-bracket fatigue sensor for crack detection monitoring near stiffeners in bridge girdersTelehanic, Boris; Mufti, Aftab; Thomson, Douglas; Bakht, Baidar; Murison, Evangeline; 10.3217/978-3-99161-057-1-032This study investigates an innovative pi-bracket sensor system integrating distributed fiber optic sensing with Brillouin Optical Time Domain Analysis to detect cracks in bridge girders near stiffeners. The system is designed to overcome challenges in crack detection at these critical locations. Experimental validation was conducted on a 3-meter steel beam featuring a welded stiffener positioned 25mm from a simulated crack. An aluminum pi-bracket served as a mounting device for the fiber optic sensor. Comparative analysis between experimental measurements and finite element simulations demonstrated the system's ability to detect crack openings as small as 0.2mm. Abaqus Finite Element Analysis predicted strain values of 145μɛ, while laboratory experiments recorded 129μɛ, a discrepancy of approximately 11%. Strain concentrations were localized to the regions where the pi-bracket was in direct contact with the beam. The strong correlation between computational models and empirical data substantiates the efficacy of the proposed sensing system. These findings highlight the system's potential for structural health monitoring of bridge infrastructure, particularly for detecting and quantifying cracks near stiffeners.
• Monitoring of civil engineering structures – current and future use casesGeorge, Joyal K.; von Wangenheim, Kristian; Kaplan, Felix; Schneider, Ronald; Hindersmann, Iris; 10.3217/978-3-99161-057-1-033Monitoring represents an effective approach for addressing the diverse challenges associated with the maintenance of civil engineering structures. It contributes to improving both the availability and safety of these structures. By increasing the amount of information available about the structure, monitoring supports better-informed decisions regarding its preservation. Due to the complexity of monitoring applications, specific use cases are outlined. A key advantage of these use cases is that new technologies can be tested within well-defined and limited scopes. The use cases “monitoring of known, localized damage,” “monitoring of known deficits identified through reassessment or resulting from outdated design procedures” and “monitoring aimed at assessing traffic loads and their effects” currently account for the majority of implemented monitoring measures. Their practical implementation is demonstrated through case studies from the Brandenburg State Road Authority. Additional use cases, such as “monitoring to support structural inspections” - for example through the use of imaging techniques - and “monitoring of major structures,” such as large viaducts, are gaining importance, with initial practical examples already present in Europe. Future applications reveal potential for expanded use, particularly in the context of “monitoring to support predictive lifecycle management.” This will become increasingly important in the implementation of digital twins, as announced in the national BIM master plan. Furthermore the concept of a “Birth Certificate” is intended to establish a reference state of the structure prior to commissioning, which can then be used for comparison with future measurements over time. The integration and interaction of these individual use cases pave the way for the implementation of digital twins.
• A Structural Health Monitoring Framework For Intelligent and Sustainable Infrastructure: A Conceptual PerspectivePedram, Masoud; Taylor, S; Hamill, Gerard; 10.3217/978-3-99161-057-1-034This paper presents a vision for next-generation Artificial Intelligence (AI) based structural health monitoring (SHM) systems through the lens of DREAM-SHM: a framework comprising Dynamic, Real-time, Evaluative, Adaptive (AI-based), Modular, Self-diagnostic, Holistic, and Multi-sensory principles. The aim is to enable smart infrastructure that can sense, and evolve corresponding to structural behaviour, material degradation, environmental effects, and changing operational or economic constraints. The paper reviews current SHM technologies, highlighting the strengths and limitations of contact-based sensors, such as accelerometers, strain gauges, fibre optic sensors, and non-contact approaches including vision-based systems, infrared thermography, radar, and ultrasonic techniques. Emphasis is placed on their integration with wireless sensor networks, Internet of Things (IoT) platforms, and Artificial Intelligence (AI) for advanced data fusion, anomaly detection, and predictive analytics. The computational aspects underpinning SHM systems, such as cloud-edge processing, machine learning, and multi-modal sensor data integration, are described to enable timely and informed decision-making. In addition, the paper situates DREAM-SHM within the context of sustainability, demonstrating how adaptive and intelligent SHM systems support the goals of circular economy and net-zero carbon by prolonging asset life, reducing maintenance burdens, and improving environmental responsiveness. This work outlines a pathway toward structurally intelligent and resource-efficient infrastructure.
• Best Practices for Data Acquisition System Design: Practical Wisdom for Engineers and PractitionersSimmonds, Tony; Randall, Brent; 10.3217/978-3-99161-057-1-035As global infrastructure ages and demands on new and existing structures increase, effective monitoring programs are essential for managing risk and public safety. This paper provides a practical guide for practitioners to design and implement structural health monitoring (SHM) systems, leveraging the combined expertise of the authors, who have extensive experience with leading equipment manufacturers. Building on the 10 Steps of Data Acquisition System Design, the paper outlines best practices for developing robust monitoring systems tailored to bridges, dams, and other critical infrastructure. These steps include defining objectives, selecting appropriate sensors, communications design, data acquisition (DAQ) system design, power system considerations, civil works and mounting structures, installation, and managing data effectively. A significant focus is placed on sensor and DAQ selection, exploring their critical roles in SHM system performance. The paper covers practical techniques for selecting, installing, maintaining, calibrating, and verifying sensors across traditional analog, frequency, and digital technologies. Examples from large channel count wired systems and distributed wireless monitoring systems are shared to illustrate diverse applications. This paper aims to deliver actionable insights and practical wisdom, equipping attendees with the tools to overcome real-world challenges and achieve reliable, scalable, and long-lasting SHM implementations.