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Non-destructive corrosion inspection of reinforced concrete structures using an autonomous flying robot
... Fully actuated UAVs [9][10][11] employ non-collinear propeller configurations, effectively decoupling attitude control from force generation. This design allows them to exert greater forces and perform more intricate manipulation tasks, albeit at the cost of increased construction and control complexity. ...
... Similarly, ref. [10] introduces a UAV with tilting propellers to interact with curved surfaces, while ref. [11] extends this concept with a rolling sensor to evaluate concrete corrosion along structural surfaces. ...
... For contact inspection tasks, such as those performed on concrete walls or bridges [4,6,11], the force requirements often exceed the capabilities of under-actuated UAVs. Addressing these requirements does not necessarily demand the added complexity of fully actuated systems. ...
With the growing adoption of Unmanned Aerial Vehicles (UAVs) in industrial and commercial sectors, the limitations of traditional under-actuated multirotors are becoming increasingly evident, particularly in manipulation tasks. Limited control over the thrust vector direction of the propellers, coupled with its interdependence on the vehicle’s roll, pitch, and yaw moments, significantly restricts manipulation capabilities. To address these challenges, this work presents a control framework for multirotor UAVs equipped with thrust-vectoring components, enabling enhanced control over the direction of lateral forces. The framework supports various actuator configurations by integrating fixed vertical propellers with horizontally mounted thrust-vectoring components. It is capable of handling horizontal thruster setups that generate forces in all directions along the x- and y-axes. Alternatively, it accommodates constrained configurations where the vehicle is limited to generating force in a single direction along either the x- or y-axis. The supported UAVs can follow transmitter commands, setpoints, or predefined trajectories, while the flight controller autonomously manages the propellers and thrusters to achieve the desired motion. Moment evaluations were conducted to assess the torsional capabilities of the vehicles by varying the angles of the thrusters during torsional tasks. The results demonstrate comparable torsional magnitudes to previously studied thrust-vectoring UAVs. Simulations with vehicles of varying inertia and dimensions showed that, even with large horizontal thruster offsets, the vehicles followed desired trajectories while maintaining stable horizontal orientation and smaller attitude variations compared to normal flight. Similar performance was observed with positive and negative vertical offsets, demonstrating the framework’s tolerance for thrusters outside the horizontal plane.
... 8 (LiDAR) for 3D crack detection, 10 sclerometers, 10 Infrared thermography (IRT) cameras, 7,11,12 and many others. Digital image processing tools 13 based on AI techniques have also been developed, allowing the detection, mapping in real-time 11 and quantification of structural damage, 12,14,15 and, for example, the automated detection of exposed steel rebars and corrosion hazards 16 or also for structural vibration measurement and condition assessment. 17 The use of robotic tools not only allows the collection of data to be automated but also allows tools to transfer and record this data, making it natural to process it numerically and place it in a digital model. ...
The last decade has seen the dynamic development of robotic tools, particularly the unmanned aerial vehicle (UAV). Miniaturization, improvement of control tools, and specialization of these devices have made them tools that are eagerly used by various industries, including the construction industry. Initially, UAVs were used for visual inspections; today, highly specialized devices are an increasingly important element of Structural Health Monitoring (SHM), assessing the condition of structures and estimating their load-bearing capacity. This article aims to present the current state of technology in robotic solutions in SHM, with particular emphasis on those providing possibilities for contact-based diagnostics. The work refers to wheeled robots and drones, including functional tools for diagnostics of the bond quality of the fiber-reinforced polymers strengthening overlays with the concrete surface. The paper reviews the types, scope, and methodology of data collection by robotic devices. It also shows attempts to integrate data with other SHM methods, incorporate them into the building information modeling environment, and create a digital twin of the structure. It also indicates further directions of work already initiated in the automated assessment of load-bearing capacity and estimation of the safety level of structures.
... Materials 2024,17, 6187 ...
Around the world, a significant proportion of sewers and sewer maintenance holes are constructed from concrete. Unfortunately, one major problem with concrete sewer infrastructure is corrosion caused by biogenic hydrogen sulphide, which causes major issues for concrete structural integrity. Furthermore, concrete may be significantly corroded and softened but still pass a visual inspection. The novel system presented in this paper uses a penetrometer mounted on a robotic platform to measure the depth of penetration through a corroded concrete surface. An angular mechanism is used to rotate the penetrometer to new positions as striking aggregate may result in false readings. Based on laboratory analysis, this design is capable of providing consistent and precise multiple observations for both smooth and rough surfaces, as well as for flat and curved surfaces, with 0.1 mm accuracy. The use of a remote robotic platform eliminates the hazards of confined space entry whilst providing a repeatable analysis platform.
... Their use can be based on image analysis (e.g., to support automated detection of disaster victims, even if they are partly buried in rubble; Fig. 6) (Zhang et al., 2022b), or through more mechanical abilities. This includes the ability to place sensors directly on an object, such as ground-penetrating radar (López et al., 2022) or ultrasound (Pfändler et al., 2024;Kocer et al., 2019) to test for dangerous degradation in infrastructure such as concrete sections on bridges, or robotic arms to carry out mechanical activities such as valve closing (Martinez et al., 2023;Meng et al., 2022). Increasingly solutions are appearing where UAVs are permanently positioned in weatherproof containers (drone-in-a-box principle), ready for autonomous or remotely controlled deployment, be it for maintenance or emergency response purposes (Langåker et al., 2021). ...
This chapter explains how the disaster domain has been a key application area for remote sensing since its pioneering days,
with a strong development from opportunistic post-event image acquisition to concerted and regular monitoring of socio-natural
hazards and comprehensive disaster risk management. It highlights recent technical and organizational advances,
such as those related to dynamic, multi-hazard risk assessment, as well as large satellite constellations and sophisticated
drones, with machine learning and semantic scene analysis playing increasing roles in data processing. Finally, the chapter
discusses the limitations of remote sensing data and gaps in how they are used.
... However, the extensive data collection required for these methods, which often involves scanning a closemeshed grid, poses a major challenge, especially in the case of large structures or limited resources. The traditional answer has been automation through robotic data collection [2], but scalability and resource optimization issues remain. ...
Advancing towards a circular economy necessitates the efficient reuse and maintenance of structuralmaterials, which relies on accurate, non-damaging condition assessments. This paper introduces aninnovative AI-driven adaptive sampling (AS) technique integrated with Non-Destructive Testing(NDT) to optimize this process. AS focuses on critical data points, reducing the amount of data neededfor precise assessments—evidenced by our method requiring on average only 7 samples for LogisticRegression and 8 for Random Forest, contrasted with 29 for traditional sampling.By reducing the necessity for extensive data collection, our method not only streamlines the assessmentprocess but also significantly contributes to the sustainability goals of the circular economy. These goalsinclude resource efficiency, waste reduction, and material reuse. Efficient condition assessmentspromote infrastructure longevity, reducing the need for new materials and the associated environmentalimpact.The circular economy aims to create a sustainable system where resources are reused, and waste isminimized. This is achieved by extending the lifecycle of materials, reducing the environmentalfootprint, and promoting recycling and reuse. Longevity directly contributes to the circular economy bymaximizing the utility and lifespan of existing materials and structures. Longer-lasting infrastructuremeans fewer resources are needed for repairs or replacements, leading to reduced material consumptionand waste generation. This aligns with the circular economy's principles of sustainability and resourceefficiency. This research not only advances the field of structural health monitoring but also aligns withthe broader objective of enhancing sustainable construction practices within the circular economyframework.
... With continuous research in artificial intelligence and automation, recent works have demonstrated the potential of autonomous mobile robots in various industrial applications, including infrastructure inspection [1,2], construction [3,4], and physical interaction [5,6]. However, modern robots often still lack the decisional autonomy required for deployment in real-world scenarios with uncertain operating conditions. ...
... With continuous research in artificial intelligence and automation, recent works have demonstrated the potential of autonomous mobile robots in various industrial applications, including infrastructure inspection [1,2], construction [3,4], and physical interaction [5,6]. However, modern robots often still lack the decisional autonomy required for deployment in real-world scenarios with uncertain operating conditions. ...
In real-world industrial environments, modern robots often rely on human operators for crucial decision-making and mission synthesis from individual tasks. Effective and safe collaboration between humans and robots requires systems that can adjust their motion based on human intentions, enabling dynamic task planning and adaptation. Addressing the needs of industrial applications, we propose a motion control framework that (i) removes the need for manual control of the robot's movement; (ii) facilitates the formulation and combination of complex tasks; and (iii) allows the seamless integration of human intent recognition and robot motion planning. For this purpose, we leverage a modular and purely reactive approach for task parametrization and motion generation, embodied by Riemannian Motion Policies. The effectiveness of our method is demonstrated, evaluated, and compared to \remove{state-of-the-art approaches}\add{a representative state-of-the-art approach} in experimental scenarios inspired by realistic industrial Human-Robot Interaction settings.
Structural health monitoring (SHM) has proven effective in early damage detection and in facilitating structural condition assessment. Conventional SHM systems feature comprehensive sensing for large infrastructures, such as long-span bridges and high-rise buildings. However, the high cost of these systems limits their feasibility for small to medium-sized structures. Inspired by lightweight design principle from the automotive industry, lightweight monitoring offers a promising complementary approach to conventional SHM. This paper provides an overview of the concepts, techniques, methodologies, and applications of lightweight monitoring for SHM. For sensing devices, non-contact, wireless, and robotic sensing are explored for their potential to enable fast and convenient data acquisition. For monitoring scheme, the concept of targeted sensing is introduced as an alternative to comprehensive sensing, focusing on the monitoring of critical structural behaviors using purpose-built devices. Additionally, the development of cloud-edge-end collaborative framework enables optimized deployment of computing resources for SHM. With regard to data analysis, the paper examines methods for data preprocessing, data fusion, and structural evaluation, with particular emphasis on artificial intelligence-driven approaches that enable fast and automatic analysis. Finally, this paper offers insights into the future of lightweight monitoring in SHM. By organizing and clearly identifying SHM techniques suitable for lightweight monitoring practices, this review serves as a practical guide for advancing the adoption of lightweight SHM and provides a foundation for further innovation in this field.
In this article, we present a feedback control method for tactile coverage tasks such as cleaning or surface inspection. Although these tasks are challenging to plan due to the complexity of continuous physical interactions, the coverage target and progress can be effectively measured using a camera and encoded in a point cloud. We propose an ergodic coverage method that operates directly on point clouds, guiding the robot to spend more time on regions requiring more coverage. For robot control and contact behavior, we use geometric algebra to formulate a task-space impedance controller that tracks a line while simultaneously exerting a desired force along that line. We evaluate the performance of our method in kinematic simulations and demonstrate its applicability in real-world experiments on kitchenware. Our source codes, experiment videos, and data are available at https://sites.google.com/view/tactile-ergodic-control/ .
Damage identification, both in terms of size and location, in bridges is important for timely maintenance and to avoid any catastrophic failure. An earlier experimental study showed that damage in a steel box girder orthotropic plate can be successfully detected using the measured vibration acceleration data. In this study, the wavelet packet decomposition (WPD) method is used to analyze the measured vibration acceleration responses and then the estimation of the permutation entropy (PE) on the re-constructed signals. A damage index is then defined based on the permutation entropy difference (PED) between the damaged and the healthy conditions to detect the location and size of the damage. The method is further validated through the finite element (FE) model of a steel box girder and the computed vibration acceleration responses when subjected to the sinusoidal excitations at different frequencies. In addition, the robustness of the methodology under different white noise interference conditions is also verified. The results show that the proposed methodology can effectively identify the location of human-made damage and accurately estimate the degree of damage under different frequencies of sinusoidal excitation. The method has shown a strong anti-noise property.
A wall climbing inspection robot has been designed to climb on safety critical concrete structures by adhering to reinforcement steel bars (rebars) using permanent magnets to generate the adhesion forces. Simulation and experimental validation has been performed to determine the optimum flux focusing magnet configurations with the robot operating on 30 to 35mm of concrete cover over rebars arranged in different patterns. The goal of adhesion force optimization is to be able to carry a ground penetrating radar (GPR) sensor which detects rebar corrosion, concrete delamination and concrete cover deterioration. The autonomous robot uses an ultra-wide band (UWB) localisation system and GPR data to control its motion trajectories to avoid regions where there is insufficient density of rebars. Non-destructive testing (NDT) inspection data acquired by GPR is transmitted wirelessly to a ground station for processing and monitoring by NDT technicians.
With recent advances in non-contact sensing technology such as cameras, unmanned aerial and ground vehicles, the structural health monitoring (SHM) community has witnessed a prominent growth in deep learning-based condition assessment techniques of structural systems. These deep learning methods rely primarily on convolutional neural networks (CNNs). The CNN networks are trained using a large number of datasets for various types of damage and anomaly detection and post-disaster reconnaissance. The trained networks are then utilized to analyze newer data to detect the type and severity of the damage, enhancing the capabilities of non-contact sensors in developing autonomous SHM systems. In recent years, a broad range of CNN architectures has been developed by researchers to accommodate the extent of lighting and weather conditions, the quality of images, the amount of background and foreground noise, and multiclass damage in the structures. This paper presents a detailed literature review of existing CNN-based techniques in the context of infrastructure monitoring and maintenance. The review is categorized into multiple classes depending on the specific application and development of CNNs applied to data obtained from a wide range of structures. The challenges and limitations of the existing literature are discussed in detail at the end, followed by a brief conclusion on potential future research directions of CNN in structural condition assessment.
Aerial manipulation aims at combining the versatility and the agility of some aerial platforms with the precision and the dexterity of robotic arms. This letter tries to collect the results reached by the research community so far within the field of aerial manipulation, specially from the technological and control point of view. A brief literature review about general aerial robotics and space manipulation is carried out as well.
The impact-echo (IE) acoustic inspection method is a non-destructive evaluation technique, which has been widely applied to detect the defects, structural deterioration level, and thickness of plate-like concrete structures. This paper presents a novel climbing robot, namely Rise-Rover, to perform automated IE signal collection from concrete structures with IE signal analyzing based on machine learning techniques. Rise-Rover is our new generation robot, and it has a novel and enhanced absorption system to support heavy load, and crawler-like suction cups to maintain high mobility performance while crossing small grooves. Moreover, the design enables a seamless transition between ground and wall. This paper applies the fast Fourier transform and wavelet transform for feature detection from collected IE signals. A distance metric learning based support vector machine approach is newly proposed to automatically classify the IE signals. With the visual-inertial odometry of the robot, the detected flaws of inspection area on the concrete plates are visualized in 2D/3D. Field tests on a concrete bridge deck demonstrate the efficiency of the proposed robot system in automatic health condition assessment for concrete structures.
Degradation processes in reinforced concrete structures that affect durability are partially controlled by transport of aggressive ions through the concrete microstructure. Ions are charged and the ability of concrete to hold out against transfer of ions greatly relies on its electrical resistivity. Hence, a connection could be expected between electrical resistivity of concrete and the deterioration processes such as increase in permeability and corrosion of embedded steel. Through this paper, an extensive literature review has been done to address relationship between concrete electrical resistivity and its certain durability characteristics. These durability characteristics include chloride diffusivity and corrosion of reinforcement as these have major influence on concrete degradation process. Overall, there exists an inverse or direct proportional correlation between these parameters. Evaluated results, from measuring the concrete electrical resistivity, can also be used as a great indicator to identify early age characteristics of fresh concrete and for evaluation of its properties, determination of moisture content, connectivity of the micropores, and even condition assessment of in-service structures. This paper also reviews and assesses research concerning the influential parameters such as environmental conditions and presence of steel rebar and cracks on measuring electrical resistivity of concrete. Moreover, concrete resistivity concept, application, and its various measurement techniques are introduced.
This paper describes an innovative protocol for full field mapping of a large civil structures involving effective use of Unmanned Aerial Vehicles (UAVs) to enable real time structural health monitoring. The proposed frameworks integrates UAVs, image processing and data acquisition procedures for crack detection and assessment of surface degradation. A novel approach is proposed combining hat transform and HSV thresholding technique for crack detection. In addition, grey scale thresholding is employed for the measurement of surface degradations. A Demonstration multi-rotor UAV model is developed to carry out full field inspection of civil structures and real time testing is performed in our large university campus. In order to provide sophisticated monitoring platform for users, a MATLAB Graphical User Interface (GUI) is developed to analyse real time as well as acquired images and the results are validated successfully. The obtained results confirms that, the envisaged approach is the foundation for cost effective and time compressing solution for monitoring of large civil structures.
The article discusses the half-cell potential measurements for reinforced concrete structures. The half-cell potential measurements can be performed on structures with ordinary or stainless steel reinforcement. The method can be applied regardless of the depth of concrete cover and the rebar size and detailing. The measurements indicate corroding rebars not only in the most external layers of reinforcement facing the reference electrode but also in greater depth.
This article presents and validates active interaction force control and planning for fully actuated and omnidirectional aerial manipulation platforms, with the goal of aerial contact inspection in unstructured environments. We present a variable axis-selective impedance control which integrates direct force control for intentional interaction, using feedback from an on-board force sensor. The control approach aims to reject disturbances in free flight, while handling unintentional interaction and actively controlling desired interaction forces. A fully actuated and omnidirectional tilt-rotor aerial system is used to show capabilities of the control and planning methods. Experiments demonstrate disturbance rejection, push-and-slide interaction, and force-controlled interaction in different flight orientations. The system is validated as a tool for nondestructive testing of concrete infrastructure, and statistical results of interaction control performance are presented and discussed.
Bridge condition rating is a crucial variable used for prioritisation of bridge needs in bridge management systems (BMSs). At present, bridge rating is predominantly based on visual inspections. A practical method incorporating non-destructive testing (NDT) results for rating bridges in a BMS is not available. In this study, an integrated rating method for reinforced concrete bridges based on both visual inspection and multiple NDT techniques with the ultimate goal of incorporating it into BMSs was developed. The method uses a multi-component and multi-modal NDT application at network-level with improved testing speed. The application results of four non-destructive techniques including visual inspection, polarisation resistance, penetration resistance, and pulse velocity on a reinforced concrete bridge network of 100 bridges are presented. At bridge level, a multi-component approach was used, including decks, girders, cap beams, piers, and abutments. A novel method for NDT-based reinforcement corrosion rating was developed. Correlation among NDT variables was also investigated and the results are presented. Multiple linear regression models were developed using ANOVA analyses. Only the statistically significant regressors with the largest partial F-statistic were included in the model formulas. The expected weights of the four evaluation criteria in the formula were obtained by combining the results of two techniques: statistical data available in literature on the frequency of use of NDT techniques for bridge inspection, and a three-level analytical hierarchy process (AHP) based on expert survey. Application of three NDT techniques to inspections of concrete bridges, determination of NDT ratings using the integrated rating formula, and incorporation of the resulting ratings into a BMS for bridge ranking can be performed using the proposed methodology.
Ein Großteil der Schäden an Ingenieurbauwerken wird durch Korrosion verursacht. In der vorliegenden Arbeit wurden repräsentative Erhaltungsprojekte von Ingenieurbauwerken in der Schweiz detailliert analysiert. In den untersuchten Fällen zeigte sich, dass 56 % der Instandsetzungskosten (± 11 %) direkt durch die Korrosion verursacht werden. Bei Ingenieurbauwerken im Straßennetz der Schweiz liegen die direkt durch Korrosion versursachten Kosten somit schätzungsweise bei 260 bis 510 Mio. CHF pro Jahr, also gegen 1 000 CHF pro Minute. Dies entspricht 0,08 % des Bruttoinlandprodukts. Nebst dem Straßennetz werden Korrosionskosten auch an anderen Ingenieurbauwerken erwartet, etwa an der Bahninfrastruktur, im Energiesektor oder bei Wohn‐ und Bürobauten. Diese wurden hier nicht berücksichtigt; ebenso wurden die indirekten Kosten (Staus, Umweltbelastung, etc.) nicht quantifiziert. Die hier ermittelten direkten Kosten durch Korrosion an Ingenieurbauwerken im Straßennetz der Schweiz stimmen in der Größenordnung mit den für die USA vorliegenden Daten überein und können daher möglicherweise auch auf andere industrialisierte Länder angewandt werden. Aufgrund dieser volkswirtschaftlichen Bedeutung ist es zentral, das Korrosionsphänomen bestmöglich unter Kontrolle zu haben. Dies bedingt dringend technologische Innovationen und eine zeitgemäße Ausbildung von Fachkräften im Bauwesen.
Omnidirectional MAVs are a growing field, with demonstrated advantages for aerial interaction and uninhibited observation. While systems with complete pose omnidirectionality and high hover efficiency have been developed independently, a robust system that combines the two has not been demonstrated to date. This paper presents VoliroX: a novel omnidirectional vehicle that can exert a wrench in any orientation while maintaining efficient flight configurations. The system design is presented, and a 6 DOF geometric control that is robust to singularities. Flight experiments further demonstrate and verify its capabilities.
KeywordsOveractuatedOmnidirectional MAVGeometric control
Today's modern cities depend on basic services such as water and sewer systems including tunnels, which are supported by a pervasive infrastructure. The structural condition of these places is naturally prone to deterioration. Therefore, regular inspections are required for early detection of damage and material failure. It is envisaged that robotic systems may provide an up-to-date solution for this inspection task. Considering the challenging conditions in the surrounding environments, unmanned aerial vehicles (UAVs) may be a potential candidate to meet the need for both purely visual (contactless) and subsurface (contact-based) inspection functionalities. When the interaction with an uncooperative target is required, the UAV needs to be aware of the forces arising during the contact phase. This stage brings additional challenges including a variable center of gravity as well as the moment of inertias due to the shift in the attached parts, sliding on the target because of the surface characteristics and reaching desired interaction levels out of the equilibrium point without crashing the dedicated sensors while creating counter forces (reactions) in a desired manner. At the same time, ultrasonic inspection requires uninterrupted contact in certain force ranges. In order to address these factors in a compact and feasible manner, an optimization algorithm consisting of nonlinear moving horizon estimation (NMHE), which is a part of nonlinear model predictive control (NMPC) is proposed. In this algorithm, the baseline model of the UAV is augmented by the external forces where uncertainties, modeling mismatches and disturbances are lumped. Therefore, the NMHE has estimated these values in an online manner. In a simultaneous fashion, the identified external forces are fed into the NMPC to physically interact with the ceiling during the contact phase. The experimental inspection data is collected while autonomously staying in predefined constraint limits. It is observed that the complete inspection data is obtained and streamed via Bluetooth when the force on the ultrasonic tool reached 5.5 N level. The external force update coming from the estimation allows the proposed approach to reach these interaction levels.
Unmanned Aerial Systems (UAS – a.k.a. drones) have evolved over the past decade as both advanced military technology and off-the-shelf consumer devices. There is a gradual shift towards public use of drones, which presents opportunities for effective remote procedures that can disrupt a variety of built environment disciplines. UAS equipment with remote sensing gear present an opportunity for analysis and inspection of existing building stocks, where architects, engineers, building energy auditors as well as owners can document building performance, visualize heat transfer using infrared imaging and create digital models using 3D photogrammetry. This paper presents a comprehensive review of various literature that addresses this topic, followed by the identification of a standard procedures for operating a UAS for energy audit missions. The presented framework is then tested on the Syracuse University campus site based on the literature review to showcase: 1) pre-flight inspection procedure parameters and methodologies; 2) during-flight visually identified areas of thermal anomalies using a UAS equipped with Infrared (IR) cameras and; 3) 3D CAD modeling developed through data gathered using UAS. A discussion of the findings suggests refining procedure accuracy through further empirical experimentation, as well as study replication, as a step towards standardizing the automation of building envelope inspection.
This paper presents a literature survey on aerial manipulation. First of all, an extensive study of aerial vehicles and manipulation/interaction mechanisms in aerial manipulation is presented. Various combinations of aerial vehicles and manipulators and their applications in different missions are discussed. Next, two main modeling methods and a detailed investigation of existing estimation and control techniques in aerial manipulation are explained. Finally the shortcomings of current aerial manipulation research are highlighted and a number of directions for future research are suggested.
Zunehmendes Verkehrsaufkommen, höhere Gesamtgewichte und klimatische Veränderungen haben in den letzten Jahrzehnten den Alterungsprozess der Infrastruktur verstärkt. Der daraus resultierende Anstieg der Erhaltungskosten erfordert einen optimierten Einsatz der Erhaltungsmittel der Betreiber. Basis des Erhaltungsmanagements ist ein umfassendes Wissen über den Zustand der Bauwerke. Die aktuellen Richtlinien (z. B. DIN 1076, RI‐EBW‐PRÜF) definieren Prüfintervalle, die üblicherweise mehrere Jahre umfassen; wobei viele Methoden der Zustandserfassung auf einer handnahen Prüfung beruhen. Ergebnisse der Zustandsbewertung werden in Kennzahlen zusammengefasst, die einen objektiven Vergleich gestatten. Die daraus ableitbare Priorisierung unterstützt die reaktive Substanzerhaltung bei der Optimierung der Ressourcen. Schädigungsprozesse können damit aber über große Zeiträume ihr destruktives Potenzial zur Entfaltung bringen. Besonders bei großen Bauwerken zieht dies einen höheren Aufwand für Prüfung und Instandhaltung nach sich. Automatisierte, multimodale Zustandserfassungssysteme, wie der hier vorgestellte BetoScan, unterstützen daher gleichermaßen Bauwerksprüfer wie Betreiber. Durch einen schnelleren Prüfprozess, höhere Reproduzierbarkeit der Ergebnisse sowie eine größere Informationsbasis unterstützt BetoScan eine optimale Diagnose und fördert damit Konzepte einer proaktiven Substanzerhaltung mit dem Ziel, Schädigungsprozesse frühzeitig zu erkennen und zu beseitigen.
In order to minimize the costs, risks, and disruptions associated with structural inspections, robotic systems have increasingly been studied as an enhancement to current inspection practices. Combined with the increasing variety of commercially available robots, the last two decades have seen dramatic growth in the application of such systems. The use of these systems spans the breadth of civil infrastructure works, and the variety of implemented robotic systems is growing rapidly. However, the highly interdisciplinary nature of research in this field means that results are disseminated across a broad variety of publications. This review paper aggregates these studies in an effort to distill the state of the art in inspection robotics, as well as to assess outstanding challenges in the field and possibilities for the future. Overall, analysis of these studies illustrates that the design of inspection robots is often a case-specific compromise between competing needs for sophisticated inspection sensing and for flexible locomotion in challenging field environments. This review also points toward the growing use of robots as a platform to deploy advanced nondestructive evaluation (NDE) technologies, as well as the expanded use of commercially available robotic systems. Two key outstanding challenges for future researchers are suggested as well. The first is the need for more sophisticated, and inspection-driven, robot autonomy. The other is the need to process and manipulate the massive data sets that modern robots generate.
Application of maintenance to ensure the safety, extend the service life and reduce the life-cycle cost of civil structures is important. In this paper, a new inspection method is proposed using a robot which can effectively approach target sections of structures, such as areas that are either too narrow or too dangerous to approach and perform both visual and detailed inspection with various devices. The small-sized self-propelled robot was initially developed. The test model can freely move on the surfaces of various types of structures. Next, the function to detect the deterioration of concrete or steel surfaces by attached cameras to the robot was examined. Moreover, a function was installed to identify the location of the robot automatically using a phase-only correlation method and to determine structural behaviours using an accelerometer. Finally, the applicability of robotic movement and all installed functions was tested on an existing bridge.
Concrete quality can be tested on site by coring or non-destructive testing. This paper describes a method based on the four-point or Wenner procedure for measuring electrical resistivity, deployed on a bridge over the River Danube between Vidin, Bulgaria and Calafat, Romania. Due to the high reinforcement density in bridge members, a model had to be developed to measure resistivity in the concrete cover and the instruments conventionally used had to be modified. The findings for the over 900 measurements recorded, which covered most of the bridge, showed that the concrete quality was higher than specified in 99.25 % of the readings.
This paper describes an investigation into the collapse of a single-span, segmental post-tensioned concrete bridge. The structure consisted of precast units stressed together both longitudinally and transversely. It was built in 1953 and collapsed at approximately 7:00 A.M. on December 4, 1985. There had been no evidence of distress before failure, and there was no traffic on the bridge when it collapsed. The investigation showed that the bridge had deteriorated because of corrosion of the tendons where they passed through the segmental joints. Corrosion had occurred because the tendons had been inadequately protected at the joints, and this had enabled chlorides to enter the ducts. It is believed that de-icing salts were the major source of chlorides, although it is possible that dune sand had been included in the mortar used to fill the transverse joints. The results cause concern about the condition of other post-tensioned concrete bridges in which tendons pass through joints.
Concrete resistivity measurements are favored for durability assessments due to the relatively simple measurement procedure and the documented correlations between concrete resistivity and transport properties, as well as reinforcement steel corrosion rates. For the measurement, it is common to use a four-point probe with four equally spaced electrodes (spacing distance a) and convert the measured resistance R into apparent resistivity with the so-called Wenner expression, ?app = 2paR. By means of experimental measurements and model simulations, the present study confirmed that the application of this formula is adequate, even if most of the assumptions underlying its derivation are violated. The reasons for this are systematically discussed. The experimental results also indicate that measurements with common four-point setups overestimate the resistivity with respect to bulk resistivity measurements. This is likely due to the presence of coarse aggregates that distort the current field at the sense electrodes.
RABIT (Robotics Assisted Bridge Inspection Tool) provides rapid and automated condition assessment of concrete bridge decks using multiple nondestructive evaluation (NDE) technologies integrated into a robotic platform. In particular, the system is designed to characterize three most common deterioration types in concrete bridge decks: rebar corrosion, delamination, and concrete degradation. For that purpose, the system uses four technologies: electrical resistivity (ER), impact echo (IE), ground-penetrating radar (GPR), and ultrasonic surface waves (USW). In addition, the RABIT has two cameras for high resolution bridge deck imaging to provide a permanent record of the visible deterioration and surface features. The autonomous data collection is complemented by an advanced data analysis, interpretation and visualization. The most of the data analysis is conducted in real or near real time. The results are presented in terms of condition maps and condition indices. The data visualization platform facilitates an intuitive 3-dimensional presentation of the main three deterioration types and deck surface features. The data collection, analysis, and results presentation by the RABIT system are described and illustrated.
Reinforcement corrosion might lead to cracking and spalling of the concrete cover owing to the volume expansion associated with the deposition of some of the possible corrosion products. This is not only aesthetically unpleasing, it might also accelerate deterioration processes or become a safety issue for passing traffic. The present paper discusses first the mechanisms of carbonation- and chloride-induced reinforcement corrosion and considers the chemistry of aqueous iron in order to identify the type of corrosion products as well as their location of formation. Furthermore, practical examples are summarised in order to compare the documented behaviour of a number of real structures with the theoretical considerations made. It is shown that for the case of purely chloride-induced (pitting) corrosion, precipitation of corrosion products is strongly delayed or may even not occur. Implications are discussed with respect to time-to-corrosion prediction models and visual inspection of reinforced concrete structures. Both the theoretical considerations and the practical experience illustrate that relying on outwardly visible signs to detect internally on-going corrosion must be done with caution if localised reinforcement corrosion cannot be excluded.
Based on construction dates and observed time to corrosion induced damage, the future need for repair of reinforced concrete motorway bridges in The Netherlands is predicted. Due to the age distribution and in particular the relatively short life of conventional repairs, the need for maintenance will increase steeply over the next few decades. It appears that a back log of postponed maintenance exists, which aggravates the problem. This steep rise may be mitigated by the application of various modern techniques for assessment, prevention, monitoring, and protection, that each have a good track record but are not widely used. Various factors that oppose the application of such innovations in the area of concrete maintenance are discussed.
The determination of concrete resistivity via the Wenner probe has become an established non-destructive technique either as to verify performance based concrete quality or to assess the chloride diffusivity of existing concrete structures. However, various factors can result in misinterpretations when taking the resistivity measurement. In this study, the finite element method (FEM) is employed to assess the effects of specimen geometry, specimen size, rebar presence, cover depth, multi-layered resistivity, and the combined effects of these factors. The findings confirm that the influence can be quantified by FEM computations to obtain normalization parameters (i.e. cell constants) or to better interpret field resistivity measurements.
This paper introduces a climbing robot for corrosion monitoring of reinforced concrete structures such as cooling towers, dams or bridges. The robot combines a vortex adhesion mechanism with a wheel electrode sensor for potential mapping of the concrete surface. A detailed description of the system is presented first. A special effort was made during the design in order to develop a lightweight device. The climbing robot is well suited for rough surfaces and can climb on vertical surfaces or move upside-down. The experiments that have been done to validate the concept are presented afterwards. They show that the climbing robot has several advantages over the traditional corrosion monitoring technique. This robot will therefore provide engineers in charge of infrastructure maintenance with the means to do their job much better than they can today. It offers them a way to circumvent all present barriers and brings a radical innovation in this area.
Concrete is the largest volume material used by man and is irreplaceable for innumerable large infrastructure developments. From the point of view of natural resources, ecology and economy, it is virtually impossible to imagine substituting concrete by any other material. However, because of the large volumes used, its total energy and CO2 footprint is important. This material therefore needs to be improved and small steps can have a big impact, once again because of the large volumes involved. This review paper examines some of the routes that may be followed to further improve the environmental performance of concrete.
This paper analyzes why and how nondestructive testing (NDT) measurements can be used in order to assess on site strength of concrete. It is based on (a) an in-depth critical review of existing models, (b) an analysis of experimental data gathered by many authors in laboratory studies as well as on site, (c) the development and analysis of synthetic simulations designed in order to reproduce the main patterns exhibited with real data while better controlling influencing parameters. The key factors influencing the quality of strength estimate are identified. Two NDT techniques (UPV and rebound) are prioritized and many empirical strength-NDT models are analyzed. It is shown that the measurement error has a much larger influence on the quality of estimate than the model error. The key issue of calibration is addressed and a proposal is made in the case of the SonReb combined approach. It is based on the use of a prior double power law model, with only one parameter to identify. The analysis of real datasets from laboratory studies and from real size buildings show that one can reach a root mean square error (RMSE) on strength of about 4 MPa. Synthetic simulations are developed in order to better understand the role played by the strength range and the measurement error. They show that the number of calibration cores can be significantly reduced without deteriorating the quality of assessment. It is also shown that the optimal calibration approach depends on the number of cores.
Half-cell potential mapping techniques have been used successfully to indicate regions where steel reinforcement is corroding unseen beneath the surface of concrete structures. It has been proposed that a mapping of the electrical resistivity of the concrete can be used in conjunction with the potential method to assess the severity of the corrosion problem in addition to the location of corroding regions. In this Paper, some of the advantages and drawbacks are discussed, with different methods of making measurements in situ. Practical tests and theoretical studies were conducted to assess the accuracy and reliability of different methods of measurement. The influence of both the ambient environmental conditions and the specimen configuration on the resistivity measurement were also investigated. Practical guidance is given to engineers in resistivity measurement techniques and in the interpretation of results.
Elektrochemische Potentialmessungen (auch Potentialfeldmessungen) haben sich seit Jahren bewährt, Bereiche mit aktiver chloridinduzierter Korrosion an tausalzexponierten Bauwerken, wie z. B. Brückentafeln sowie Zwischendecks und Bodenplatten von Parkhäusern und Tiefgaragen nachzuweisen.
Bereits 1990 erschien die erste Fassung des Merkblatts B3 der DGZfP. Das DAfStb Heft 422 (1991) – Prüfung von Beton Empfehlungen und Hinweise zu DIN 1048 – enthielt die Potentialfeldmessung bzw. das Merkblatt B3 im Anhang. In Deutschland liegen somit zwei Jahrzehnte Erfahrungen mit den entsprechenden Regelwerken und natürlich auch in der praktischen Anwendung vor. In der Praxis zeigte sich jedoch auch, dass die Anwendung verbessert werden muss. Die Potentialmessung wurde vielfach sogar falsch durchgeführt, wichtige Messungen fehlten und auch die Interpretation bzw. Bewertung der Messergebnisse erfolgte nicht mit dem erforderlichen ingenieurmäßigen Sachverstand. Häufig erfolgte die Bewertung nur auf Grundlage des amerikanischen Regelwerks ASTM Standard C 876–91, welches sich auch aufgrund der unterschiedlichen Bauweisen in Deutschland jedoch nur sehr bedingt eignet. Dies und auch das Vorliegen neuer technischer und wissenschaftlicher Erkenntnisse veranlassten den DGZfP-Fachausschuss für Zerstörungsfreie Prüfung im Bauwesen den Unterausschuss Korrosionsnachweis bei Stahlbeton zu beauftragen, das Merkblatt B3 zu überarbeiten und neu heraus zu geben. Das neue Merkblatt wurde schließlich im April 2008 veröffentlicht.
Ziel des nachfolgenden Beitrags ist es, das Potentialmessverfahren in kurzer Form darzustellen, insbesondere jedoch das Merkblatt B3 der Fachöffentlichkeit vorzustellen, da sich immer wieder gezeigt hat, dass dieses Merkblatt bei Anwendern und Auftraggebern nur sehr wenig bekannt ist.
Der Inhalt des Merkblatts B3 wird nachfolgend in Auszügen dargestellt, erläutert und Hinweise zur praktischen Ausführung und Bewertung der Potentialmessung gegeben. Ferner werden an einigen Stellen Hintergrundinformationen gegeben, die im Merkblatt B3 nicht enthalten sind. Auf neuere wissenschaftliche Erkenntnisse wird verwiesen. Die Kapiteleinteilung des Merkblatts B3 wird übernommen. Manche besonders wichtige Passagen des Merkblatts werden weitgehend wörtlich übernommen, wobei diese Passagen der besseren Lesbarkeit halber nicht extra gekennzeichnet werden.
A new method is described for thein-situ measurement of electrical resistivity of concrete structures. The method is based on the early work of J. Newman who calculated
the electrolyte resistivity between a disk and a counter electrode located at infinity. This method has the advantage compared
with Wenner's of using a single small electrode for the measurements. In this paper, results are presented comparing this
method with Wenner's and with results carried out using a conductivity cell in electrolytes. Finally, values of resistivity
are compared to corrosion intensity, and a threshold for active corrosion is suggested.
On décrit une nouvelle méthode de mesure de la résistivité électrique du béton dont la technique est basée sur un travail
ancien de J. Newman qui avait calculé la résistivité entre un disque et une électrode auxiliaire placée à l'infini. Comparée
à la méthode de Wenner, cette méthode présente l'avantage de n'utiliser, pour les mesures, qu'une petite électrode. Dans cet
article, on présente les résultats de la comparaison établie avec la méthode de Wenner et avec les résultats obtenus avec
une cellule de conductivité placée dans les électrolytes. Enfin, on compare les valeurs de la résistivité du béton avec celles
de l'intensité de la corrosion et on suggère un seuil de corrosion active.
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Corrosion for Civil Engineers Part 4: Potential Measurement to Detect Corrosion of Steel in Concrete
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