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

INE/AUTC 10.0

Real-Time structural health monitoring for concrete beams: a cost-effective 'Industry 4.0' Solution using Piezo Sensors

Purpose: This research paper adopts the fundamental tenets of advanced technologies in industry 4.0 to monitor the structural health of concrete beam members using cost effective non-destructive technologies. In so doing, the work illustrates how a coalescence of low-cost digital technologies can seamlessly integrate to solve practical construction problems. Methodology: A mixed philosophies epistemological design is adopted to implement the empirical quantitative analysis of ‘real-time’ data collected via sensor-based technologies streamed through a Raspberry Pi and uploaded onto a cloud-based system. Data was analysed using a hybrid approach that combined both vibration characteristic based method and linear variable differential transducers (LVDT). Findings: The research utilises a novel digital research approach for accurately detecting and recording the localisation of structural cracks in concrete beams. This nondestructive low-cost approach was shown to perform with a high degree of accuracy and precision, as verified by the LVDT measurements. This research is testament to the fact that as technological advancements progress at an exponential rate, the cost of implementation continues to reduce to produce higher accuracy ‘mass-market’ solutions for industry practitioners. Originality: Accurate structural health monitoring of concrete structures necessitates expensive equipment, complex signal processing and skilled operator. The concrete industry is in dire need of a simple but reliable technique that can reduce the testing time, cost and complexity of maintenance of structures. This was the first experiment of its kind that seeks to develop an unconventional approach to solve the maintenance problem associated with concrete structures. This study merges industry 4.0 digital technologies with a novel low-cost and automated hybrid analysis for real-time structural health monitoring of concrete beams by fusing several multidisciplinary approaches in one integral technological configuration

Imaging reinforced concrete: A comparative study of Ground Penetration Radar and Rebarscope

Geophysical techniques have been playing a very vital role in subsurface imaging in the recent past. Technology has been making it both reliable and convenient to utilize non-destructive geophysics techniques like Ground Penetration Radar, Induction current based Rebarscope, Seismic methods, ERT, etc. The applications range from shallow subsurface investigation of Bridge decks to old tunnels, mapping of rabars in a pre-existing construction and analyzing the concrete strength. The thesis constitutes of a comparative study and analysis of a Ground Penetration Radar system and a Rebarscope. Individual parameters obtained directly from the study and obtained indirectly from the study shall be analyzed for a better quantitative understanding of their variation and errors to optimize the utility of the instruments individually. Data obtained from both Ground Penetration Radar system and Rebarscope would be compared for accuracy in determining the rebar depth. For the experiments, pre-designed concrete slabs are constructed with rebars at various depths and defects in concrete. Furthermore, a combination of both the instruments is used to minimize errors and to achieve better control over the intrinsic and extrinsic errors of the instruments to undertake real world studies with better dependency. A calibration, comparative and combination study of Ground Penetration Radar and Rebarscope is important for the very purpose of better understanding of the quality of concrete, especially in its initial stages of degradation. The amplitude variation in the signal and dielectric permittivity of the concrete indicates concrete quality. The study illustrate the superiority of the Ground Penetration Radar system, but in cases of highly varying degradation and construction errors Rebarscope plays key role in accurate depth estimation of the reinforcement rebars. The study highlights some limitations of GPR surveys and proceeds to address the limitations by utilizing a Rebarscope in combination with GPR system --Abstract, page iii

Degradation Monitoring Systems for a BIM Maintenance Approach

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

Ultrasonic NDT Methods for the Evaluation of Post-Tensioned Systems with Flexible Fillers

Non-destructive evaluation of post-tensioned structures with flexible fillers is desperately needed due to their rapid implementation in the State of Florida, primarily in roadway structures. This study provides an overview of existing evaluation methods for traditional post-tensioned structures with cementitious grouts and further explores two promising methods to be applied to flexible filler systems. The first method, diffuse ultrasound spectroscopy, indirectly evaluates posttensioned structures by quantifying the severity of microcracking in the structure. Microcrack detection is accomplished by processing received waveforms generated with a pitch-catch transducer configuration. The second method, coda-wave interferometry, measures the velocity variation at the tail end of waveforms, known as the coda, between varying stress states of a structure. The velocity variation can be correlated to cracking events, structural yielding, and stress level changes. First, preliminary testing was done for both methods to find the optimal test setup and validate the methods\u27 efficacy. Algorithms were developed for both promising methods using the preliminary testing data for development. Next, the methods underwent experimental testing composed of direct compression and 3-point load testing on normally reinforced and posttensioned small-scale beams. The experiments show the methods\u27 effectiveness in indirectly evaluating the health of the post-tensioning system with flexible fillers. Overall, the two methods prove to be very promising and are recommended to be explored in further studies

Evaluation Of Concrete Degradation Using Acoustic Emission: Data Filtering And Damage Detection

The prevalence of aging and deteriorating infrastructure in the U.S. has raised concerns regarding its level of serviceability, reliability, and vulnerability to natural disasters. This issue has gained attention recently and efforts are being conducted to accelerate the delivery of enhanced nondestructive testing (NDT) and structural health monitoring (SHM) methods. Acoustic emission (AE) is a strong candidate for these applications due to its high sensitivity and potential for damage detection in different materials. However, several challenges associated with the technique hinder the development of automated, reliable, real-time SHM using AE. This study aims to advance the use of AE for condition assessment of concrete structures by addressing two main challenges. The first is AE data filtering to exclude irrelevant noise and wave reflections. Effective filtering and data reduction enhances the quality of the data and lowers the cost of its transfer and analysis; ultimately increasing the reliability of the method. The second issue is detecting slow rate material degradation mechanisms in concrete. For example, alkali-silica reaction (ASR) affects civil infrastructure around the nation, and available condition assessment methods for this type of damage are either invasive or not feasible for field conditions. Despite the awareness of ASR concrete deterioration; there is lack of research investigating the ability of AE to detect and assess it. In addition, recent laboratory investigations have shown promising results in detecting and evaluating damage related to corrosion of steel in concrete using AE. However, the results have not been extended to field applications. This dissertation includes three studies that address the aforementioned issues. In the first study, wavelet analysis was used to study the distribution of energy in AE signals in the time-frequency domain. Criteria to differentiate between AE signals from artificial sources (pencil lead breaks) and wave reflections were developed. The results were tested and validated by applying the developed filters on data collected from actual cracking during load testing of a prestressed concrete beam. The second study presents a laboratory test conducted to assess the feasibility of using AE to detect ASR damage in concrete. Accelerated ASR testing was undertaken with a total of fifteen specimens tested; twelve ASR and three control specimens. The results of this study showed that AE has the potential to detect and classify ASR damage. Relatively good agreement was obtained with standard ASR measurements of length change and petrographic examination. The third study discusses a field application for long-term, remote monitoring of damage due to corrosion of reinforcing steel and potential thermal cracking in a decommissioned nuclear facility. The structure was monitored for approximately one year and AE damage detection and classification methods were successfully applied to assess the damage at the monitored regions. This study also included an accelerated corrosion test conducted on a concrete block cut from a representative structure. The studies included in this dissertation provide: 1) an innovative approach for filtering AE data collected during cracking of concrete, 2) a proof of concept study on detecting ASR damage using AE, and 3) field application on AE monitoring of corrosion damage in aging structure. The outcomes of this research demonstrate the ability of AE for condition assessment, structural health monitoring, and damage prognosis for in-service structures

Acoustic emission analysis of prestressed concrete structures

This thesis examines the role of Acoustic Emission (AE) as a non-destructive testing (NDT) technique for prestressed and reinforced concrete structures. The work focuses on the development of experimental techniques and data analysis methods for the detection, location and assessment of AE from prestressed and reinforced concrete specimens. This thesis reveals that AE can be used to detect the onset of corrosion activity in wire in the interface between prestressed concrete and mortar as found in prestressed concrete pipes. Furthermore, this technique can be used to locate the corrosion activity on different size prestressed concrete samples. By correlation between three parameters of classical AE analysis techniques (traditional parameters), damage can be detected and located whilst the corrosion area, macro crack and crack propagation can be identified. However, it cannot classify the crack type. Different damage modes, including corrosion activity, micro/macro cracking formation, crack propagation and wire failure generate different types of AE signals with varying amplitudes and absolute energy emitted. A novel analysis approach has been used on composite materials (concrete, mortar and steel) to evaluate differing crack types by a combination of the classical acoustic emission analysis technique and advanced analysis Rise time / Amplitude (RA) and Average Frequency (AF), results proved the effectiveness of the developed techniques for damage detection and classification crack types. The relationship between RA value and AF value can be used to determine the crack area and classify it as either tensile crack type, other type (shear movement) or no crack. The results of the research have demonstrated that the AE technique is valid in larger scale monitoring and hence the potential for monitoring real structures such as prestressed concrete pipes. Use of Kernel Density Estimation Function (KDEF) provides improved visualisation of the data to represent clearly the RA/AF values. Key Words: Acoustic Emission, Corrosion, Reinforced Concrete, Prestressed Concrete, Micro and Macro Concrete Cracks, Crack classification, Source Location, Damage Assessment, Monitoring

Localization and detection of wireless embeddable structural sensors using an unmanned aerial vehicle in the absence of visual markers

The objective of this thesis is to develop a fully integrated UAV based platform for autonomous collection of data from embedded sensors. Passive (battery-less) embedded sensors provide means for periodic long-term monitoring of civil structures like bridges. However, collection of data from these sensors requires extensive manual effort of locating them. UAVs can automate this process, although localization of these embedded tags in absence of visual markers pose a challenge. A RF (13.56MHz) reader is used to capture data from RF tags wirelessly. Different tag coil sizes are tested to observe effects on read range as well as to characterize the interaction volume between reader and tag. The UAV platform is integrated with the RF reader to autonomously capture data from tags using GPS based localization. Different sensor configurations are tested and characterized to meet the requirements of X,Y,Z localization set by the reader and tag interaction volume. Flight characteristics are also observed for various UAV navigation parameters. Results suggest that by using low-cost RTK GPS unit, the UAV is capable of detecting and localizing RF tags without any visual markers or aides.Electrical and Computer Engineerin