An Introduction to Non Destructive Evaluation and Structural Health Monitoring through a Web Based Virtual Laboratory

Presenting author(s): Mr Xiangang Lai

Co-Authors: Shi Ye, Ms Emily Le Blanc, Dr A Emin Aktan, Dr Ivan Bartoli, Mr Franklin Moon, Dr Kurt Sjoblom, Mr Marcello Balduccini, Mr Matteo Mazzotti, Mr Qiang Mao, Mr Mustafa Furkan, Mr Charles T Young, Mr Yundong Li, Mr Stylianos Livadiotis, Mr John Braley, Dr Hoda Azari

Room: Regency Ballroom ABC | 9:05 AM Monday, August 27, 2018

Non Destructive Evaluation (NDE) techniques, such as Impact Echo, Ultrasonic Surface Wave, Ground Penetrating Radar have been widely applied to assess the condition of infrastructure components such as reinforced concrete decks of highway bridges. NDE techniques have the potential to uncover internal defects as well as to estimate material properties with a relatively high spatial resolution at the material level. Other approaches that are often referred to as Structural Health Monitoring (SHM) provide information at a somewhat lower spatial resolution but the measurements attempt to assess the overall behavior of a structure (structural level assessment). Both NDE and SHM share an inherent complexity and need proper understanding of the challenges, potentials, and shortcomings to extract reliable information. The authors are attempting to unveil some of these complexities to a relatively broad range of users including infrastructure owners, researchers, and industry stakeholders through the creation of a virtual laboratory website. The creation of this virtual laboratory represents the primarily goal of an ongoing federally sponsored research study. The website presents NDE techniques as well as an introduction to SHM tools. The Virtual laboratory contains interactive modules where users can learn through simulations or observe real NDE data. The virtual laboratory also attempts to show how different tools can be integrated to improve the decision making process in infrastructure management through case studies on real operating infrastructures with performance concerns. The paper provides highlights of the current content of the virtual laboratory.

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Acoustic Density Evaluation – a New Approach for Advanced Ultrasonic Testing of Concrete Structures

Presenting author(s): Mr Roman Pinchuk

Co-Authors: Mr Andrey Bulavinov, Mr Andrey Samokrutov

Room: Garden State Ballroom | 9:05 AM Monday, August 27, 2018

In view of aging civil infrastructure made of reinforced concrete the demand on intelligent diagnostic tools and quality assurance for integral assessment of infrastructural objects will increase. Ultrasonic material testing in its both functions – flaw detection and mechanical property evaluation – offers one of the possible instrumentation for the quality assurance in construction industry. Due to its unique deep penetrating capability, ultrasonic testing in certain cases remains the only suitable method for evaluating internal structure of large constructions. For overcoming natural inspectability limitations of coarse grained materials like concrete, a novel method for acoustic evaluation of density gradients – shorty “Acoustic Density” evaluation technique – is proposed. It allows extracting valuable additional information about slight acoustic impedance changes in the material by means of statistical processing of individual wavelets obtained by Dry Point Contact (DPC) transducer arrays and coherent integration of the impedance gradients. In the current contribution, the basic principles of the new technique are explicated and few application cases are cited showing the potential of the novel approach for variety of practical ultrasonic inspection tasks in the construction industry.

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Nondestructive Testing in Civil Engineering – Requirements for the Practical Application and State of the Art in Switzerland (Research Project AGB 2012/016 for the Federal Roads Office; FEDRO)

Presenting author(s): Mr Sascha Feistkorn

Co-Authors: Mr Bjorn Muhlan, Mr Yves Schiegg, Mr Andreas Hasenstab, Mr Daniel Algernon

Room: Regency Ballroom ABC | 9:30 AM Monday, August 27, 2018

In the presented research project, the essentials for the most relevant field applications of NDT-CE were analyzed. This includes the assessment of the practical needs, typical inspection tasks as well as the limitations of the applied methods regarding their reliability and accuracy. Among others, the analysis of former field inspections in Switzerland was carried out in more than 40 different individual projects as well as the development of new theoretical approaches. Therefore, the research partners conducted an extensive study in collaboration with large construction companies to analyze the scope of NDT-CE methods applied in the past decades in Switzerland. The study focused on Ground Penetrating Radar (GPR) and Ultrasonic Testing (UT) and investigated the challenges of inspecting structures in the field. As a result, the most relevant difficulties were identified depending on field conditions, such as reinforcement ratio, moisture content, tendon duct material or the size of a discontinuity of the component inspected. To predict the success of a field inspection, the methods of POD (Probability of Detection) and GUM (Guide to the Expression of Uncertainty in Measurement) were used to quantify the performance and the accuracy of Radar and Ultrasound for common practical inspection tasks under different field conditions. As one result, typical penetration depth values of GPR applied on concrete have been calculated. Furthermore, the estimated success of the respective methods is provided as a function of different field conditions.

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The Application of RTM Technology for the Evaluation of Pulse-Echo and Linear Array Ultrasonic Measurements in Concrete

Presenting author(s): Dr Klaus Mayer »

Co-Authors: Ms Maria Grohmann

Room: Garden State Ballroom | 9:30 AM Monday, August 27, 2018

Reverse Time Migration (RTM) is a well-known seismic exploration technique for mapping the subsurface with a given velocity profile, but has hardly been used in non-destructive ultrasonic testing up to now, since an enormous numerical and storage technology effort is required to carry out the calculations. New concepts for storing the time steps of the wave propagation now allow the calculations to be carried out on workstation computers. On the basis of implementations for the acoustic and elastic finite integration technique (AFIT and EFIT), various scenarios for the application of the ultrasonic technology at tendon ducts in concrete are presented and compared with the results of SAFT reconstructions.

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Decommissioned Bridges: Ideal Test Objects for Demonstrating the Capabilities of Non-Destructive Testing Methods

Presenting author(s): Dr Martin Friese »

Co-Authors:

Room: Regency Ballroom ABC | 10:15 AM Monday, August 27, 2018

Specially designed test specimens are ideal during the development of non-destructive testing methods and to determine their theoretical performance. During the design you can focus on the particular test task. But if you want to demonstrate the capabilities of NDT methods to bridge owners, you need something more realistic. Highly realistic test specimens are quite expensive - and they are still specimens. Decommissioned bridges (which will later be replaced) or components taken from them have proven to be ideal testing objects. First of all, they are not only "highly realistic", they are real. It's not expensive to built them, they already exist. And during their demolition it's possible to use destructive methods to verify the NDE results - which wouldn't be possible at bridges under service.

During the past years, the Federal Ministry of Transport and Digital Infrastructure (German: Bundesministerium für Verkehr und digitale Infrastruktur, abbr. BMVI) funded several demonstration projects at decommissioned bridges which were supervised by the Federal Highway Research Institute (German: Bundesanstalt für Straßenwesen, abbr. BASt). Their outcome will be summarized in this paper . Typical test tasks were the investigation of the inner structure of PC bridges (e.g. locating reinforcement and internal tendons), the detection of grouting faults and the detection of fractures in prestessing wires caused by stress induced corrosion.

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Nondestructive Evaluation of a Retaining Wall of Former Coal Mine Plant

Presenting author(s): Dr Hans-Georg Herrmann

Co-Authors: Dr Herbert Wiggenhauser, Mr Matthias Behrens, Mr Ralf Moryson, Mr Sergey Pudovikov, Ms Dorothee Moser

Room: Garden State Ballroom | 10:15 AM Monday, August 27, 2018

Historical structures without documentation about their inner material and architecture represent a special challenge for condition monitoring with non-destructive testing methods. The measurements presented here are carried out on a retaining wall of a former coal mine in Germany. The 9 m high and 286 m long wall shows different cover materials like concrete, masonry or quarry stone. Information about reconstruction and extension steps are unknown. Three vertical lines along the wall were selected in representative areas to evaluate the usefulness of non-destructive testing methods. Therefore, the retaining wall has been investigated using Ground Penetrating Radar (GPR) with two low frequency antennas (200 and 400 MHz) and Large Aperature UltraSound (LAUS) to gather information about the condition and inner structure of the wall. In addition, infrared thermography is planned for further investigation about the wall condition. The LAUS results showed the layer structure at one line where the wall was enforced by a concrete shell and were unspecific regarding the inner structure beyond the first layer. GPR results could be collected much faster and showed some internal features. Penetration was limited to 2-3 m due to the high attenuation in the material. The discussed measurements and results reflect the high requirements for NDT of such objects. Furthermore, the area of effective measurement differs for each method and also the time and effort required by the respective method.

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Test Specimen Concepts in Regard to Quality Assurance and Validation of Nondestructive Testing in Civil Engineering

Presenting author(s): Mr Daniel Algernon

Co-Authors: Dr Ralf W Arndt, Mr Walzer Denzel, Mr Bente Ebsen, Mr Sascha Feistkorn, Dr Martin Friese, Mr Christian Grosse, Ms Susanne Kathage, Ms Sylvia Kessler, Mr Christian Kopp, Mr Stefan Kuttenbaum, Mr Carsten Lohse, Mr Stefan Maack, Dr Ernst Niederleithinger, Mr Martin Schickert, Mr Gunnar Schroder, Mr Alexander Taffe, Mr Juri Timofeev, Dr Andrei Walther, Martin Wilcke, Ms Julia Wolf

Room: Regency Ballroom ABC | 10:40 AM Monday, August 27, 2018

The process of ensuring reliability of NDT applications contains various aspects, such as determining the performance and probability of success, the uncertainty in measurement, the provision of clear and functional procedures and ensuring the correct application accordingly. Test specimens have become powerful elements in supporting many of these aspects. Within the committee for NDT in Civil Engineering (NDT-CE) of the German Society for Nondestructive Testing (DGZfP), the subcommittee on Quality Assurance (UA-QS) therefore addresses the design and the integration of test specimens in the quality assurance process. Depending on the specific purpose, the requirements on test specimens can vary significantly based on the defined simulated scenario. The most prominent purposes of test specimens might be seen in providing references for inspection systems in regard to function control, calibration and validation. Further aspects can be parametric studies, basic investigation of physical principles related to NDT or a simplified and therefore comprehensive demonstration of inspection concepts (e.g. for teaching purposes).The specific purpose of a test specimen dictates the requirements regarding its conception, including the exact design, the material or the fabrication accuracy and the conditioning. In the development of a general guideline by the UA-QS for application-specific procedures and their validation, the use of test specimens is addressed and specific concepts for test specimen design are made. This includes the analysis of the measurement process regarding any given application, deriving an adequate calibration approach for it and designing test specimens (calibration specimens) accordingly. Furthermore, it includes the validation of the procedure taking into account all conditions related to the specific application in the field. The validation requires a statistically sufficient number of trials. Thorough evaluation of each trial can only be established if the ground-truth is known. Therefore, test specimens providing a realistic but controlled simulation of the inspection problem are valuable and indispensable elements in the validation process. The requirement of being fully realistic will often not be possible to fulfill due to practical restrictions. Any aspect that cannot be included in the simulation realistically, needs to be simulated conservatively. This again, requires a sufficient understanding of the inspection principle and technique to ensure conservativeness. Among other quality-assurance-related aspects, the UA-QS establishes concepts and guidelines regarding sound and efficient approaches for the specific purposes of test specimens. This subcommittee brings together representatives of different groups along the entire value chain of NDT-CE, including researchers, practitioners, manufacturers and clients. They all work together in establishing a common understanding and level of quality assurance in the industry.

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Use of Ultrasonic Shear Waves For Determination of the Depth of Surface-Opening Cracks in Reinforced Concrete Elements

Presenting author(s): Mr Shibin Lin

Co-Authors: Dr Hoda Azari, Mr Sadegh Shams

Room: Garden State Ballroom | 10:40 AM Monday, August 27, 2018

Determination of the depth of surface-opening (visible) cracks is of critical importance for evaluating structural safety of reinforced concrete elements. However, it has been challenging to accurately determinate the crack depth with traditional methods. Based on the diffraction of ultrasonic horizontal-shear (SH) waves at the bottom edge of a crack, this study develops a new method using ultrasonic test equipment that has a set of transducers as transmitters and a set of transducers as receivers in a pitch-catch configuration (e.g., EyeCon). A pulse of SH waves is sent out from the transmitters at one side of the crack, and the SH waves after diffraction from the crack tip is received by the receivers at the other side of the crack. SH waves is superior to other waves in data interpretation, because SH waves do not have mode conversion after diffraction. Thus, it is very easy and accurate to identify the travel time of diffracted SH waves in time domain. The crack depth can be calculated with the travel distance of SH waves and the spacing between the transmitter and the receivers. This method is validated with the numerical and experimental data from four case studies. Results of these case studies indicates that this method can significantly improve the accuracy in determination of the depth of surface-open cracks compared to the P-waves based method (i.e., impact-echo method and ultrasonic longitudinal stress waves method).

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Quality Management of Concrete Construction by Digitizing the Process Chain from Batching Plant to Building

Presenting author(s): Mr Edgar Bohner

Co-Authors:

Room: Regency Ballroom ABC | 11:05 AM Monday, August 27, 2018

Recently in Finland, a series of incidents with poor concrete quality related to entrained air received lots of attention not only among experts in concrete industry and research but as well in public media and the Finnish society. These incidents resulted in major economic consequences and called into question current technical knowledge applied on the construction site.
Enquiries showed that concrete with insufficient quality could not be identified and rejected before casting due to deficiencies in quality control and the current manual testing procedures. Therefore, the Finnish concrete industry together with experts from research communities and academia started looking for a new quality management of fresh and young concrete by utilizing digital solutions, sensing technologies and new developments in data management and integrity. In order to digitalize the entire process chain it is necessary to measure crucial material properties during mixing, transporting, pumping, casting and curing of the concrete. Established sensing technologies are combined with novel applications that are currently under development. It is of particular importance that the concrete quality is followed through the entire process, starting in the batching plant and followed up until the concrete reaches a predefined age in the structure. Consequently, many stakeholders will produce, share and receive data to promote quality control and assurance.
The integrity and liability of the data is secured based on blockchain technology.
The data can be integrated into building information models (BIMs) as part of new
approaches in adding as-built information in real-time into BIM platforms and
thereby supporting decision-making of architects, engineers and building
experts in the construction process.

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In Situ Inspection of Concrete Structures Using a Rolling Ultrasound Scanner

Presenting author(s): Mr Kamal Raj Chapagain

Co-Authors: Mr Werner Bjerke, Mr Terje Melandso, Mr Philippe Olivier, Dr Sanat Wagle

Room: Garden State Ballroom | 11:05 AM Monday, August 27, 2018

NDT methods such as ultrasonic testing are useful for monitoring of infrastructures like bridges, railways and roads during regular operation to prevent failure and increase safety. It is relatively simple and less time consuming, hence is one of the most effective ways for inspection and assessment of damage of concrete structures. However, the concrete structures pose many challenges for inspection due to wide distribution in size of aggregates and its inhomogeneity. A broadband multilayer piezoelectric PVDF array transducer was used to develop an ultrasonic roller scanning system for concrete structure inspection. Two eight element transducer array units were assembled in two separate rollers to operate in transmission (Tx) and receiver (Rx) modus (Pitch and Catch mode). The Tx and Rx modus configuration will increase electrical shielding and thereby reducing the capacitive currents set up during pulse excitation. The coupling of ultrasonic signal from transducer assembly in rollers to the concrete surface are achieved by dry elastomers rings. A large area of concrete surface was scanned with relatively short inspection time. By using a customized electronic platform and our own adaptation of cross-track and along-track Synthetic Aperture Focusing Technique (SAFT) algorithm, a good image was acquired. Further signal processing and visualization was adapted. The broadband characteristics obtained from the PVDF transducer make it possible to use a wide range of adjustable operational frequencies. This is highly beneficial for concrete imaging where typically aggregates with a large variation in sizes will limit the image quality and enforce a tradeoff between penetration depths and resolution. The scanner is equipped with a rotational encoder that keeps track of positional information with reference to a starting point during scanning. A handheld display unit is capable of displaying real-time 3D images of the internal state of the concrete structures make it easier to identify and locate the defects. The developed ultrasonic scanner was used to locate and analyze the defects inside the different concrete structures. Several artificial defects such as delamination, air tube, and rebar were imposed inside the different concrete blocks. Each transducer element of Tx roller was fired with Ricker approximation pulse of 150 kHz central frequency. This pulse was received by each element of Rx roller after propagating inside the concrete. The roller was moved with constant scanning speed on concrete surface and the large amount of A-scan data were acquired. Then, these acoustic data were used to create B, C and D-scan images using SAFT algorithm after signal processing. A user friendly interface with full 3D video presentation in real time for on site or for post analyzes has been developed.

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Consistency of the Bridge Inspection Program of New York State

Presenting author(s): Mr Anil Agrawal »

Co-Authors: Dr Sreenivas Alampalli, Dr Glenn A Washer

Room: Regency Ballroom ABC | 11:30 AM Monday, August 27, 2018

A 2001 Federal Highway study on reliability of bridge inspections identified significant variability in visual inspection ratings of bridges. The New York State Department of Transportation (NYSDOT) maintains an inventory of over 17,000 highway bridges across the state. Bridge inspectors are required to assign a condition rating for up to 47 structural elements of each bridge, including 25 components of each span of a bridge, in addition to the general components common to all bridges based on visual inspection of these elements. The bridge condition rating scale ranges from 1 to 7, 7 being new and 1 being in failed condition. An extensive investigation has been carried out through the inspection of 4 selected bridges by a team of 21 bridge inspectors in the New York State. The objectives of this study have been to (i) carry out a quantitative evaluation of the variability associated with the New York State Bridge Inspection policies and procedures, and (ii) provide suggested improvements to bridge inspection policy and procedures and training. This presentation will present the outcome of this study.

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Thermal Modulation of Nonlinear Acoustic Wave for Microcracking Damage Evaluation in Concrete

Presenting author(s): Dr Jinying Zhu

Co-Authors:

Room: N/A | 11:30 AM Monday, August 27, 2018

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Aerial Vs Vehicle-Based Infrared Thermography for Bridge Deck Delamination Detection

Presenting author(s): Mr Evan Guarino

Co-Authors: Mr Kenneth Maser, Mr Adam Carmichael

Room: Regency Ballroom ABC | 1:25 PM Monday, August 27, 2018

Vehicle-based infrared thermography surveys have provided state Departments of Transportation with a powerful tool to supplement or replace traditional hammer sounding methods for detecting bridge deck delaminations. While vehicle-based surveys have greatly reduced the need for closures and the time associated with inspecting a deck, aerial infrared thermography surveys show potential for greater coverage to enhance maintenance and rehabilitation planning. Infrared data has already been collected with both vehicle-based and fixed-wing aircraft systems to assess the level of detail and accuracy of infrared data collected at altitudes around 1000 feet, and additional data will be collected in the summer of 2018. The investigations will focus on using the aerial infrared results as a high-level scoping tool for large corridors of decks where aerial data collection offers greater efficiency, with the goal of identifying decks that show little thermographic activity and can be excluded from the more detailed vehicle-based surveys. Infrared data has also been collected on a select group of decks using a drone-mounted infrared camera setup to determine if higher quality aerial data can be collected at altitudes around 100-200 feet above the deck. The use of drones could support aerial infrared thermography at the project level, providing detailed condition maps comparable to the results of a vehicle-based surveys. The paper will discuss the methodology and equipment for aerial Infrared surveys, present comparative examples of aerial versus vehicle-based deck data, and describe the implementation of aerial IR surveys at the network and project level.

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Density Prediction of Thin Asphalt Overlay during Compaction Using Ground Penetrating Radar

Presenting author(s): Dr Imad L Al-Qadi

Co-Authors: Dr Siqi Wang, Mr Shan Zhao

Room: Garden State Ballroom | 1:25 PM Monday, August 27, 2018

Thin overlay has been widely implemented as an asphalt pavement rehabilitation or preservation technique. As part of the overlay construction, monitoring of the thin overlay density change during compaction is crucial to meet the project requirements. This could be used as a quality control (QC) or quality assurance (QA) tool. Ground penetrating radar (GPR) has been used for density prediction of asphalt concrete (AC) layers. However, the accuracy of thin overlay density prediction is a challenge because of the GPR limitation in resolution and sensitivity to surface moisture during construction. In this study, a pavement model was built using gprMax, a finite difference time domain (FDTD) tool. The GPR system in the model was simplified as a transmitter and a receiver that allows receiving electromagnetic (EM) wave reflections from thin overlay surface and bottom of that layer. The surface moisture was simulated as a 2mm film with mixed electrical properties of water and thin overlay. A non-linear optimization method was used to reconstruct the GPR signal without the surface moisture effect. The resultant error of the thin overlay dielectric constant was found to be less than 6%. Validation of the proposed method using field test data from Lincoln Ave, Urbana, IL was performed. In addition to real-time monitoring of density progression during compaction, the error in predicting the AC thin overlay density was less than 2%.

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Prospects for Integrating Augmented Reality Visualization of Nondestructive Testing Results into Model-Based Infrastructure Inspection

Presenting author(s): Mr Martin Schickert »

Co-Authors: Mr Christian Koch, Mr Frank Bonitz

Room: Regency Ballroom ABC | 1:50 PM Monday, August 27, 2018

The results of non-destructive testing procedures on civil infrastructure have so far been presented on a process-related basis. To enable comprehensive quality management spanning the life cycle of a structure, it would be desirable to combine the various results, monitor their development over time, and use them for on-site maintenance tasks. In this contribution, prospects are developed for the integration of non-destructive testing results into digital building models within the framework of building information modeling (BIM). The concept thus goes beyond the use of BIM in the planning and construction phase of a structure. An innovative visualization approach using augmented reality (AR) is presented as an example of integrated visualization of planning and measurement data. An AR application has been implemented that superimposes the camera image of a tablet viewing a concrete specimen with the three-dimensional ultrasonic image and two-dimensional radar section of the interior of the specimen (actual data) and the three-dimensional planning geometry of the built-in parts (target data). When the tablet is moved or rotated, the internal view follows the camera position so that the geometric relationship between the outer and inner views is maintained. The display of the tablet thus opens up a window into the interior of the concrete structure. Steps necessary for the preparation and interpretation of non-destructive testing results are discussed, and possibilities for implementing markers for coupling the virtual world with the real world are presented. The goal is to evaluate the condition and facilitate model-based inspection and maintenance tasks directly on the structure by presenting planning data and measurement results in their real context and enriching them with additional information.

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NDT Inspection of Concrete Structures: Complementarity of Ground Penetrating Radar, Ultrasonic Tomography and Eddy Current Methods

Presenting author(s): Mr Giovanni Tambelini

Co-Authors: Mr Guido Tronca, Mr David Corbett, Mr Isaak Tsalicoglou

Room: Garden State Ballroom | 1:50 PM Monday, August 27, 2018

The state of the art of non-destructive testing applied to civil engineering has in recent years achieved many significant milestones in the field of imaging technologies for the assessment of reinforced concrete structures. The constant improvement of the available electronic components and the increased computational power of consumer-grades mobile devices are among the key factors that drove mature technologies such as Ground Penetrating Radar (GPR) and Eddy Current Testing (ECT) into products delivering new levels of accuracy and usability. At the same time, recent developments the pulse-echo-based Ultrasonic Tomography (UT) further broadened the range of applications potentially addressed. Still, there seems to be a general lack of awareness in the user community about the real potentials and main limitations of each of the three technologies. The current work focuses on the typical scenarios and the common challenges presented by tasks of embedded object detection (structural details, steel reinforcement, utility network) and flaw detection (voids, cracks, delaminations). The complementarity of the three technologies has been proven through measurements on test blocks and real-life cases. It is noted that the proper combination of technologies naturally results in more efficient workflows, increased positioning accuracy, and a less subjective, operator-dependent interpretation of the testing results.

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The Application to the Transportation Industry of Advancing Drone Use Beyond Visual Inspection: The Emergence of Contact Based Nondestructive Testing (NDT) at Height Utilizing Aerial Robotic Systems

Presenting author(s): Ms Jamie Branch »

Co-Authors:

Room: Regency Ballroom ABC | 2:15 PM Monday, August 27, 2018

Nondestructive testing (NDT) of transportation infrastructure is critical for evaluating existing material deficiencies and suitability for safe continued service. While NDT inspection programs dramatically increase the safety and integrity of our infrastructure, access requirements in performing these inspections introduces risk. Inspection sites often require access to elevated areas via equipment such as personal fall protection (safety harness and lanyard), ladders, scaffolding, inspection trucks with elevated baskets, rope work, catwalks, and rigging. Working at height creates a safety risk to the worker performing the inspection, and cause work zones and traffic detouring creating vulnerable environments that increase the potential for crashes. Unmanned aerial vehicles (UAVs), or drones, can improve the safety and efficiency of transportation infrastructure by performing the inspection with workers safe on the ground. In 2016, the American Association of State Highway and Transportation Officials (AASHTO) reported that 17 state Departments of Transportation (DOT) had either used or tested drones (i.e. UAVs) for work within the transportation industry. The Michigan DOT and Michigan Tech Research Institute conducted a study in 2014 which reported that drones were a safe, reliable, and cost-effective tool for visual bridge inspections. Drone inspections thus far have been limited to visual testing (VT). While VT is a primary method of inspection, it is not sufficient in identifying or further evaluating material deficiencies such as metal thickness, small fatigue cracks in welds, or subsurface flaws. To adequately detect these deficiencies, advanced inspection NDT methods, such as ultrasonic testing (UT), are required. Aerial robotic systems have been developed to perform advanced NDT inspection of materials at height. The emergence of this technology and current limitations are discussed in reference to the transportation industry.

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Implementation of Multi-Phase Nondestructive Evaluation Approach for Bridge Deck Evaluations

Presenting author(s): Dr Shane D Boone

Co-Authors: Mr Adam Carmichael

Room: Garden State Ballroom | 2:15 PM Monday, August 27, 2018

In 2017 BDI and Infrasense teamed to pilot a multi-phased approach for evaluating the condition of bridge decks located in Idaho, Nebraska, North Carolina, and South Carolina with partial support from the SHRP2 R06A Implementation Assistance Program. Phase 1 utilized highway-speed scanning methods including ground penetrating radar (GPR), infrared thermography (IR), and high-resolution video (HRV); and resulted in detailed quantities and maps of concrete deterioration, delamination, spalling, patching, and rebar-cover. The results of Phase 1 were used to design the Phase 2 testing program, which included rolling-speed deck acoustic response (DAR), localized manual chain-drag, coring, and chloride sampling. The combination of the Phase 1 and Phase 2 results yielded validated deck condition quantities and plan-view maps at the level of detail required for scoping rehabilitation and maintenance efforts. The purpose of the pilot projects were to provide a basis for full-scale implementation. This will ideally utilize the Phase 1 scanning methods to economically obtain network-level quantitative condition information, which can be used for programming deck preservation, maintenance, and rehabilitation projects. Phase 2 testing will be carried out for detailed scoping of these projects based on annual program priorities. This paper describes the Phase 1 and 2 deck evaluation methods and results, the correlation of these results with available ground-truth data, and the overall benefits of the multi-phased approach versus using a traditional approach.

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The Use of UAS (Unmanned Aircraft Systems or drones) for High Mast Light Pole Structural Inspections

Presenting author(s): Mr Glenn Stott »

Co-Authors:

Room: Regency Ballroom ABC | 2:40 PM Monday, August 27, 2018

The New Jersey Department of Transportation's use of innovative drone technology is rapidly changing the inspection of transportation infrastructure. NJDOT’s Structural Evaluation Team worked with the UAS Coordinator to collect data from a drone during the inspection of 250 High Mast Light Poles. This simultaneously increased safety, increased efficiency, saved time, and saved money.

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Magnetic Flux Leakage for Prestressed Concrete Beams

Presenting author(s): Dr Soundar Balakumaran

Co-Authors: Dr Steven B Chase

Room: Garden State Ballroom | 2:40 PM Monday, August 27, 2018

Corrosion of reinforcements in bridge structures is a major problem faced by bridge owners. The severity of the problem is amplified by the fact that the damage inside the concrete may not show up on the surface until significant damages have occurred. Prestressed slab structures in Virginia built since 1960s have begun showing corrosion induced deterioration. This project aims to develop a device based on Magnetic Flux Leakage (MFL) theory to detect section loss of concrete reinforcements nondestructively. This device is different from previous magnetic flux leakage inspection devices because it is measuring magnetic permeance rather than perturbations in the magnetic field. It is also unique in that it uses an array of three-axis magnetic sensors, which have only recently become available. Controlled laboratory testing is being performed to test and refine the design. Subsequent field testing will help in improving the practicality of the device.

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First Person Vision Goggles, the Next Evolution in Drone Bridge Inspection

Presenting author(s): Mr Joe Campbell »

Co-Authors: Mr Bill Lohr

Room: Regency Ballroom ABC | 3:05 PM Monday, August 27, 2018

This abstract is for a presentation based on the work the FHWA Minnesota Division has been working on to advance the opportunity and use of drones for bridge inspection. Specifically, how first person vision goggles greatly improve the field capabilities of drone inspection and when coupled with a consumer/recreational drone they are a tool that any bridge owner can afford.  The MN Division focus is on recreational are affordable options for Local Program Agencies to add drone use for their routine bridge inspections.  This work has led to the identification of a cost effective drone system that can be readily purchased at multiple outlets for under $3,000. 
First -person vision (FPV) goggles. The phrase may garner blank stares from many people who are not yet familiar with the technology. Even those who are familiar with it may have limited knowledge. Aren’t they those gadgets that can be used with a cell phone? Or, aren’t they what kids use when playing video games? Well, yes, they are most commonly known as toys or a tech accessory for computer-generated virtual reality and video games. However, they have the potential to be much more than a toy when paired with a drone to help perform bridge inspections. 

Connected directly to a drone’s video feed, FPV goggles give bridge inspectors a first -person visual that is equivalent to being 3 feet (0.9 meters) away from the components they are inspecting. This is accomplished by the drone being positioned 6 feet from the component and utilizing the two times digital zoom providing the image equivalent of 3 feet. The visual image is so clear and immersive it gives the inspector a relative image size equivalent to an 18-foot (5.5-meter), 1080p  high-definition television screen. The technology enables inspectors to visually examine bridge components easily and with enough precision to see even hairline cracks in the field, all without standard costly and hazardous inspection techniques involving ladders, climbing equipment, or snoopers bride inspection vehicle.

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Magnetic Flux Leakage (MFL) Method for Damage Detection in Internal Post-tensioning Tendons

Presenting author(s): Mr Atorod Azizinamini

Co-Authors: Mr Bernd Hillemeier

Room: Garden State Ballroom | 3:05 PM Monday, August 27, 2018

Magnetic based methods has been used to detect corrosion in steel strands in concrete bridges. The basic principle is placing permanent or electromagnet in vicinity of steel elements and investigating the changes in magnetic field through use of sensors. The most commonly used sensor is Hall Effect sensors. The use of permanent magnet facilitate field application, while use of electromagnet allows penetrating through concrete, deeper than that is allowed by permanent magnet. Several different magnetic based approaches are used in practice. Both active and residual magnetic field methods are used, each providing certain capabilities. While the basic principle is very straightforward, the analysis of data is the most challenging part of the process. This is especially true in the case of inspecting internal tendons where presence of mild steels masks the signal. A project was initiated by and supported by FDOT to develop equipment for inspecting internal tendons in segmental concrete bridge. Project is a joint activity between Florida International University and Technical University of Berlin in Berlin Germany. This presentation will provide overview of the project and joint knowledge gained by researchers in US and Germany and the timetable for having an operational version of the magnetic based equipment that will should be available in near future.

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Wireless Long term Monitoring System for Scour Critical Bridges

Presenting author(s): Mr Mehdi Kalantari

Co-Authors:

Room: Regency Ballroom ABC | 8:45 AM Tuesday, August 28, 2018

This presentation covers a breakthrough approach to scour critical bridge monitoring. Networks of connected Internet of Things (IoT) devices were used to monitor scour critical bridges in California, Pennsylvania, and Maryland. In particular, the system of connected wireless devices known as SenSpot sensors were used to monitor the tilt (orientation) of bridge piers with sub arc second accuracy. In addition, a wireless ultrasonic water level sensor was used to monitor water elevation beneath the bridge. Also, wireless solar powered cameras were used to provide constant visual feedback from the general bridge condition. To produce a model based approach, temperature was monitored at location of all sensors. For precision detection, analysis was conducted to produce a baseline model that predicts small deflections of bridge piers caused by temperature variations. The models show that in most bridges, a typical quasi-cyclic pier deflection of around 0.005 to 0.05 degrees happens, where such deflection is resulted by daily temperature changes. Once the baseline models are developed and fully verified using a few weeks of data, deviation from the models is used for detection of bridge scour. The deviation often happens in the form of a new pattern of deflection caused by temperature, or in form of excessive non-returned tilting of bridge piers, implying settling or other forms hydraulic damage. To further increase reliability of detection, data from wireless water level sensors was used to correlate changes in bridge piers deflection or orientation pattern with flood condition or periods of higher water elevation. Moreover, data from wireless camera were used to further monitor changes in pattern of rocks/sediment around bridge piers. The wireless monitoring systems of this project have been in use on several bridges owned by Maryland State Highway Administration (SHA), California Department of Transportation (Caltrans), and Pennsylvania Department of Transportation (PennDOT). The summary of breakthroughs in scour critical bridge monitoring presented in this project are as follows: (1) using battery operated IoT devices with a decade of battery life, where there is no need of wiring or access to electricity; (2) the connected IoT devices help achieve real time condition awareness on scour critical bridges; (3) automated and reliable detection methods and alert generation function, where field engineers are notified immediately when change in bridge scour condition is detected. Such notifications provide information that helps take immediate actions to ensure public safety (e.g., closing a bridge in case of severe scour condition), and to schedule maintenance or repair to address hydraulic damage in a timely fashion.

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Comparison of Ultrasonic and Laser Vibrometer Measurements for Condition Assessment of Concrete Elements

Presenting author(s): Mr Piotr Wiciak »

Co-Authors: Mr Giovanni Cascante, Ms Maria Anna Polak

Room: Garden State Ballroom | 8:45 AM Tuesday, August 28, 2018

Non-destructive ultrasonic evaluation (NDE) is a technique commonly used for the assessment of civil infrastructure and for the characterization of construction materials. This methodology provides essential information on structural integrity. However, limitations on the use of NDE techniques are still present especially on the evaluation of wave attenuation. These limitations include the assessment of the quality of coupling between transducers and tested material. Standard methods, such as ultrasonic pulse velocity, consider only the velocity of the first arriving wave. Attenuation measurements, which can be used for early damage detection, are difficult to do because ultrasonic transducers (UT) are not calibrated (i.e. unknown frequency response in engineering units). Previous research on the evaluation of transfer functions of UT has been affected by actual response of the transmitter (e.g. reproducing the actual coupling effects). This paper presents results from an experimental program designed to evaluate the effect of UT in wave attenuation measurements. The medium response is simultaneously evaluated using a state-of-the-art, calibrated laser vibrometer and UT. Ultrasonic measurements on concrete cylinders (a group of 30 cylinders of different dimensions) and the eleven concrete beams are compared with laser measurements. In order to compare the actual surface displacements with the UT responses. The information gained from these comparisons show the increasing effect of the coupling on ultrasonic readings as a function of frequency especially at the resonant peaks of the UT.

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IoT Based Permanent Eddy Current Sensor for SHM and Metal Crack-Growth-Measurements

Presenting author(s): Mr Marc Lany

Co-Authors: Mr Terry Tamutus

Room: Regency Ballroom ABC | 9:10 AM Tuesday, August 28, 2018

As developments of IoT technologies evolve, structural health monitoring (SHM) applications for civil engineering become lower cost, more robust and allow for easy sensor network integration. One of these technologies is a new innovative eddy current sensor, which is currently being produced much like a flexible film circuit board. This eddy current sensor now makes remote crack growth measurements/monitoring extremely easy. Eddy current testing has been around for more than 50 years and is a widely used and well-understood inspection technique, making it immediately acceptable for bridge NDT and monitoring. FHWA and other agencies are increasing the demand for higher NDT sensors integration to enable direct flaw detection and characterization. As such a portable system can make a baseline measurement and if cracks are discovered a permanent system can be installed. Current targeted applications are, monitoring of known cracks, crack re-initiation after a repair, or using a cylindrical probe to monitor a crack-arrest drilled-hole. Using a remote monitoring system and flexible thin film taped-on sensors, two New York State bridges have been monitored for over a year. We will present several other projects where the monitoring systems have been deployed and discuss the value for asset owners. As previously discussed this is an ideal IoT NDT/SHM technology which, could either be used for rapid NDT inspection, walk-up inspection or Structural Health Monitoring of bridges, overhead sign structures. It has a very high probability of detection and is a complementary example of NDE in SHM. Other details will also be discussed in this presentation. Authors: Bernard Revaz, Antonio Montes, Thomas Meyers, Marc Lany, and Gilles Santi

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Ultrasonic Coda Wave Monitoring to Detect Changes in Interior Stresses in Large Concrete Bridge Members

Presenting author(s): Dr Thomas Schumacher

Co-Authors: Mr Ali Hafiz

Room: Garden State Ballroom | 9:10 AM Tuesday, August 28, 2018

Condition monitoring of reinforced concrete structures has experienced increasing interest over the last decade, especially for bridges. Many types of sensors have been utilized for this purpose such as strain gages, accelerometers, displacement sensors, etc. Typically, these sensors are attached to the concrete surface and can thus detect only the changes on the surface. In contrast, ultrasonic waves propagate through the thickness of a concrete member and can thus detect internal changes. This research presents ultrasonic coda wave monitoring, which makes use of the highly sensitive diffuse portion of the recorded waveform. In the presented study, changes in the interior stresses were correlated to the changes in the ultrasonic waveforms, which were estimated using magnitude-squared coherence (MSC). This presentation provides an overview of the methodology, discusses the parameters that affect observed changes, and presents a set of laboratory experiments. Finally, the results from an in-service load test on a prestressed concrete highway bridge, where measurements during truck loading were collected on a bent column as well as a bridge girder, are presented and discussed.

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Wireless Fracture Critical Bridge Monitoring

Presenting author(s): Mr Mehdi Kalantari

Co-Authors:

Room: Regency Ballroom ABC | 9:35 AM Tuesday, August 28, 2018

This paper reports a new paradigm shifting practice in effective monitoring and condition awareness for fracture critical bridges. Since December 2015, a network of wireless Internet of Things (IoT) strain sensors have been deployed to monitor strain and temperature on fracture critical members of Gold Star Memorial Bridge in Connecticut. Built in 1943, Gold Star Memorial Bridge carries I-95 over the Thames River. With 117,000 vehicle crossings per day, the bridge is one of the busiest transportation corridors in the US. At the same time, Gold Star Memorial Bridge is one of more than 18,000 operational bridges in the US that are categorized as "Fracture Critical" by the US Department of Transportation. Due to a lack of load distribution redundancy in fracture critical bridges, failure of steel members in tension can lead to complete or partial collapse. To address the specific monitoring needs of fracture critical bridges, wireless strain sensors were attached to structural members with tension. Examples include truss members, girders, floor beams, stringers and gusset plates. To accurately detect fatigue crack formation, a number of strain analysis methods were used to detect changes in fracture critical members. The algorithms include analysis of thermal response of structural members, response to live load, and comparative analysis of thermal and live load responses on monitored members. Analysis of data provides accurate and highly reliable method to detect potential metal fatigue, change in elasticity, and change in characteristics of the fracture critical members. In addition to Gold Star Bridge, the presentation will share the success stories in other projects where the mentioned wireless strain sensors were used to monitor fracture critical bridges, namely, Monitoring Robert Norris Bridge (VA-3 over Rappahannock River, Virginia), and Monitoring I-70 over Patapsco River (Maryland).

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Contactless Visualization and Characterization of Alkali-Silica Reaction (ASR) Damage in Concrete Using Multiply Scattered Ultrasonic Wave Fields

Presenting author(s): Dr John S Popovics »

Co-Authors: Dr Homin Song, Mr Steven Feldman

Room: Garden State Ballroom | 9:35 AM Tuesday, August 28, 2018

Alkali-silica reaction (ASR) is a detrimental chemical reaction that leads to concrete degradation over time. High alkaline contents in concrete pore solutions react with amorphous silica in aggregate in concrete to form expansive gelatinous products resulting in distributed cracks in concrete. This paper reports work to detect, visualize and characterize ASR damage in concrete using multiply scattered ultrasonic wave fields. Numerical simulations and laboratory-scale experiments are performed to understand ultrasonic surface wave scattering caused by distributed cracks in concrete, distinguishing that caused by the internal aggregate network. The simulations and experimental results reveal that incident ultrasonic surface waves undergo complicated multiple scattering set up by distributed cracks. To extract the crack-induced multiply scattered ultrasonic wave fields, a frequency-wavenumber (f-k) domain signal filtering approach is proposed. The feasibility of the signal analysis approach is then established by a series of experiments on large steel reinforced concrete blocks maintained under an ASR-accelerating environment. The experimental results demonstrate that distributed cracks caused by ASR can be detected and visualized using the proposed ultrasonic signal analysis approach, even at very early stages of ASR attack. In addition, we demonstrate that the progress of ASR damage over time can be monitored, where the ASR damage extent is closely related to the extracted multiply scattered wave field energy.

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PANEL

Presenting author(s):

Co-Authors:

Room: N/A | 10:20 AM Tuesday, August 28, 2018

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Multi-Element Ultrasonic Array Technology for Inspection of Post Tension Ducts and Distributed Cracking in Concrete Structures

Presenting author(s): Dr John S Popovics »

Co-Authors: Mr Sai Kalyan Evani

Room: Garden State Ballroom | 10:20 AM Tuesday, August 28, 2018

In this work, we explore the capability of multi-element ultrasonic arrays for inspecting two important issues associated with concrete structures: i) condition of post tensioned ducts and ii) extent of distributed cracking. The presence of voids (incomplete grouting) in post-tensioned ducts increases the possibility of corrosion in steel tendons and reduces the ability of grout to transfer bond. The ability of the ultrasonic technology to distinguish between different types of grout filling conditions is determined by collecting data from a concrete slab that contains two types of post-tensioned ducts (metal and polymer) with different grout fill conditions. Raw data from the array is extracted and imaging algorithms based on reverse time migration and Kirchhoff migration are used to determine if they are effective in distinguishing different grout filling conditions. Most deterioration mechanisms in concrete, e.g. freezing and thawing action, alkali silica reactivity (ASR) and sulfate attack, manifest as zones of distributed microcracking. Ultrasonic data are collected using the ultrasonic array on concrete blocks that contain different extents of simulated distributed cracking. Raw data extracted from the device is analyzed using diffuse wave characterization techniques e.g. frequency-wavenumber (f-k) analysis and frequency-time (f-k) analysis, to assess capability of the approach to visualize and characterize distributed cracking.

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Instrumentation and Monitoring of PA Bridges

Presenting author(s): Mr Damian Silverstrim

Co-Authors: Mr Aslam Siddiqui

Room: Regency Ballroom ABC | 10:45 AM Tuesday, August 28, 2018

AI Engineers (AI) has been selected by the Pennsylvania Department of Transportation for the instrumentation and monitoring of Pennsylvania’s bridges. The scope of the project is to install short-term and long-term instrumentation on bridges to monitor several bridge types (including major structures) to capture data related to structural performance. The purpose of this project is to effectively assess the benefits of an instrumentation and monitoring program, early detection of defects and structural issues, and cost-benefit analysis on using instrumentation to successfully manage and maintain bridges. The monitoring system will detect, out-of-plane bending, crack activity, longitudinal displacement, scour events, barge-collisions with piers, and vibration of suspender cables. These systems will also evaluate the performance of steel and concrete retrofits via load testing, and characterize the thermal response of critical members. Information is collected continuously and through data analysis, AI is able to determine appropriate thresholds for both ‘warning’ and ‘alert’ level conditions and compare the data collected with expected results obtained via software modeling, previous monitoring, and/or previous design calculations. For deck suspender cable monitoring and load testing, findings and recommendations are reported to PennDOT for future design projects. Additionally, any discrepancies between the expected results and data gathered are reviewed and reported with recommendations, if necessary. The monitoring system uses a wireless structural health monitoring system and solar powered data loggers and communication gateways. This is an energy self-sufficient wireless system that can be installed and implemented quickly, and does not require permanent power sources.

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The LAUS: First Applications of a New System for Ultrasonic Imaging of Very Thick Structures

Presenting author(s): Dr Ernst Niederleithinger »

Co-Authors:

Room: Garden State Ballroom | 10:45 AM Tuesday, August 28, 2018

The LAUS (Large Aperture Ultrasonic System) hast been developed to image very thick concrete structures, which are not accessible for commercial system. The device and the corresponding software is the result of joint research of BAM, an ultrasonic instrument manufacturer and University of Kassel, Germany. It consists of 12 separate arrays of 32 point-contact shear wave transducers each, which can be deployed in flexible configurations. Each array is combined with battery and transmitter, receiver and wireless communication electronics. Two case histories are presented. First the system was deployed on a 5-m thick heavily reinforced foundation slab. The reflection of the slab’s bottom was imaged clearly. Even a multiple reflection was registers, giving hope, that even thicker elements might be imaged by the instrument. Second, the LAUS was used to investigate a massive bridge girder, where a heavy rainstorm during concreting had led to imperfections visible after removing the formwork. The LAUS could image tendon ducts in 1.8m depth and the backwall closely behind them. Some limited areas showed blurred reflections and were checked by drill holes. It occurred that these areas were affected by diffuse damage, which could be repaired by injections. Meanwhile, the LAUS been in used in underground waste deposits (nuclear and other) for quality assurance of sealing plugs. A confirmed penetration depth of about 7 m has been reached.

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ProTimB - Monitoring of Structurally Protected Timber Bridges

Presenting author(s): Dr Ralf W Arndt

Co-Authors: Mr Johannes Koch, Mr Antje Simon, Mr Markus Jahreis

Room: Regency Ballroom ABC | 11:10 AM Tuesday, August 28, 2018

Timber bridge construction has a millennia-old tradition worldwide. In the course of industrialization, other building materials have become increasingly popular. In order to build durable, durable and therefore competitive bridges made of wood, they must be protected against precipitation and the ingress of moisture. A low moisture content is the key to the durability of wooden structures. Consequently, all structural components of timber bridges should be constructively protected to reduce the negative impact of precipitation and moisture. To evaluate the efficiency of constructive wood conservation measures under real conditions a monitoring program was initiated in frame of the research project “Protected Timber Bridges” (ProTimB) sponsored by the German Federal Ministry of Education and research (BMBF). The aim of the program is to demonstrate the durability of well protected timber bridges. Furthermore, details with problems and special local climate conditions should be determined. Therefore, nine suitable bridges in Germany were equipped with a monitoring system to measure the timber moisture content and ambient climate conditions. The structural types are timber concrete composite bridges, trough bridges, arch bridges, beam bridges and truss bridges. The monitoring system works on the principle of the electrical resistance method. This method is based on the dependence between electrical resistance and material moisture content. Influencing factors are the material temperature and the wood species. The paper describes the structure and application of the monitoring system. Measurement results and conclusions are presented.

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Towards Data Based Corrosion Analysis of Concrete with Supervised Machine Learning

Presenting author(s): Dr Ernst Niederleithinger

Co-Authors:

Room: Garden State Ballroom | 11:10 AM Tuesday, August 28, 2018

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Life-cycle NDT planning of bridge fatigue-critical details based on discounted utility

Presenting author(s): Mr Minghui Cheng »

Co-Authors: Mr David Y Yang, Mr Dan M Frangopol

Room: Regency Ballroom ABC | 1:25 PM Tuesday, August 28, 2018

Bridges are subjected to fatigue damage during their service life. Nondestructive testing (NDT) can detect fatigue cracks in bridges. The information obtained from NDT can update the life-cycle performance of fatigue-sensitive bridges. The updated information can support decisions regarding repair actions to ensure serviceability and safety of bridges during their service life. As NDT brings in additional cost, NDT-based inspection should be carefully planned to maximize life-cycle performance and minimize life-cycle cost. In this paper, a novel method based on discounted utility theory is proposed to assist in decision making of NDT planning, including number of inspections and the inspection times. Compared to conventional inspection planning methods, the proposed method considers the preference of decision-makers for inspection times among schedules with similar life-cycle cost and similar life-cycle performance. It is considered herein that given the same life-cycle cost and life-cycle performance, decision makers prefer shorter inspection/repair intervals and sooner return of investment. For this purpose, discounted utility theory is employed to quantify this preference and incorporate it into the framework of life-cycle NDT planning. The proposed method is illustrated by conducting NDT planning for a fatigue-critical detail of a steel bridge. The value of discounted factor and its effect on optimal NDT plans are also investigated.

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Vertical Profiling Ultra-Seismic Inspection to Evaluate Model Pile Depths

Presenting author(s): Dr Helsin Wang »

Co-Authors: Mr Chung-Yue Wang, Mr Thanh Vinh Nguyen

Room: Garden State Ballroom | 1:25 PM Tuesday, August 28, 2018

An ultra-seismic inspection is particularly applicable to the integrity testing for the foundations supporting overwater structures, such as bridge piers or wharves with lack of access to their tops. The vertical profiling ultra-seismic method is conducted by laterally striking the foundations with a heavy hammer. The shock waves reflected at the interface between the foundation and surrounding strata are directly recorded using several receivers equidistantly installed along one side of the partially exposed foundation. Contrasting waveform imaging can estimate the interface and determine the foundation depths. In this research, the ultra-seismic tests are performed at 6 concrete model piles with diameters varying from 0.1 m to 0.25 m under both traction-free and partially embedded conditions. Instead of using the traditional time-domain waveform image analysis, the frequency analysis presents consistent results and reliable information. Herein treating a pile as a waveguide, the dispersion relation between phase velocity and frequency is presented and the propagation velocity is assumed to be three-dimensional. The estimated reflection depths at pile tips highly agree with their designate lengths. Using the resonance solutions and flexural guided wave theory is a simple and efficient method to find the resonant frequency and phase velocity by knowing pile diameter and testing results. The testing results also indicate that the resonance characteristics of flexural waves travelling in a pile are not dependent on surrounding conditions but the intrinsic physical properties in concrete piles.

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Impulse-Response Testing for Quality Assessment of Cast-in-Place Concrete Pile Foundations

Presenting author(s): Mr Stephen M Garrett »

Co-Authors: Mr Robert Hannen, Dr John Lawler

Room: Garden State Ballroom | 1:50 PM Tuesday, August 28, 2018

The presentation will show how the nondestructive test method Impulse-Response can be used for quality control and integrity assessment of cast-in-place concrete foundation piles. The test method will be briefly explained and two case studies will be presented demonstrating how Impulse-Response was used to evaluate the installation and quality issues of dry-cast concrete piles (i.e., Franki Piles) and auger cast-in-place (ACIP) piles. In both case studies, the dynamic properties determined from testing (e.g., dynamic stiffness and mobility) correlated to the condition of selected piles evaluated through boring, material sampling (i.e., core extraction and petrographic examination), and sub-surface assessment (i.e., excavation and examination). The results indicate that the test method can be effective for identifying non-conformities in tested piles of different construction methods much more quickly and efficiently than physical sampling or excavation.

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Addressing the Need to Monitor Concrete Fatigue with Non Destructive Testing: Results of Infrastar European Project

Presenting author(s): Dr Odile Abraham

Co-Authors: Dr Ernst Niederleithinger, Mr Xavier Chapeleau, Mr Piotr Klikowicz, Mr Eugen Bruhwiler, Mr Antoine Bassil, Mr Xin Wang, Mr Joyraj Chakraborty, Mr Imane Bayane, Ms Dominique Leduc, Mr Marek Salamak, Mr Andriy Katunin, Mr John Dalsgaard Sorensen

Room: Regency Ballroom ABC | 2:15 PM Tuesday, August 28, 2018

Fatigue is one of the most prevalent issues, which directly influences the service life expectancy of concrete structures. Fatigue has been investigated for years for steel structures. However, recent findings suggest that concrete structures may also be significantly subjected to the fatigue phenomena that could lead to premature failure of fatigue prone structural elements. To date, fatigue of reinforced concrete has been given little focus and knowledge on the influence factors and durability/capacity effects on this material should be improved. Current technological means to measure fatigue on civil structures like bridges and wind turbines (both onshore and offshore) are outdated, imprecise and inappropriate. Meanwhile, this topic has got much more attention as dynamic loading on concrete structures plays an increasing role, e.g. in bridges with increasing traffic and heavier trucks, in wind energy production due to inherent vibrations e.g. in offshore wind turbine support structures affected by wind and waves. The European Innovative Training Networks (ITN) Marie Skłodowska-Curie Actions project INFRASTAR (Innovation and Networking for Fatigue and Reliability Analysis of Structures - Training for Assessment of Risk) provides research training for 12 PhD students. The project aims to improve knowledge for optimizing the design of new structures as well as for more realistic verification of structural safety and more accurate prediction of the remaining fatigue lifetime of existing structures. First, the INFRASTAR research framework is detailed. Then it will be exemplified through the presentation of the major results of the four PhD students involved in the work package dealing with auscultation and monitoring. This includes the development and improvement of Fiber Optics (FO) and Coda Wave Interferometry (CWI) for crack sizing and imagery, new sensor technologies and integration, information management, monitoring strategy for fatigue damage investigation and lifetime prediction. ACKNOWLEDGEMENT : This project (2016-2020) has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 676139. The authors would like to extend a special thanks to Hakim FERRIA for the management of the project.

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Testing Seismic Techniques for Imaging Structural Defects in Engineered Drilled Shafts – A Case Study

Presenting author(s): Mr Jozef M Descour »

Co-Authors: Mr Frank Jalinoos, Mr Anil Agrawal

Room: Garden State Ballroom | 2:15 PM Tuesday, August 28, 2018

There is an urgent need for more reliable, yet quick and economical techniques for assessing integrity of underground foundation components. This presentation describes seismic investigation of stand-alone drilled shafts at two test sites—one in sandy, one in clay soil—at the National Geotechnical Experimentation Site (NGES) near the campus of Texas A&M University. Constructed in 1990s, the drilled shafts were of different lengths and containing planned or otherwise known construction-related defects. The investigation compared the results of ultra-seismic profiling, parallel seismic, and imaging structural anomalies by migration of reflected waves. Seismic waves were introduced at the above-ground surface portion of each shaft by two synchronized seismic swept-frequency sources applied at different orientations to enhance different wave modes. A hammer strike was used for comparison. Three components of seismic waves were recorded by an array of accelerometers mounted on surveyed shaft surface, and by a string of hydrophones placed in a hole cored down the center of the shaft, or a PVC-cased borehole drilled near and parallel to the shaft. The major findings of the investigation were: 1) different techniques and different wave modes appear to emphasize different structural defects; 2) a swept frequency source provided superior results as compared to non-repeatable impulsive hammer strike; 3) steel rebar cage appears to affect the survey results; and, 4) tube waves from water-filled cored holes appear useful for detecting structural anomalies intersecting the cored holes.

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Non-contact Automatic Scanning System for Concrete Pipe Assessment

Presenting author(s): Dr Suyun Ham

Co-Authors:

Room: Regency Ballroom ABC | 2:40 PM Tuesday, August 28, 2018

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Effective Dispersion Analysis of Reflections: A Nondestructive Evaluation Method for Estimating Embedded Pile Length

Presenting author(s): Mr Vivek Samu »

Co-Authors: Mr Murthy Guddati

Room: Garden State Ballroom | 2:40 PM Tuesday, August 28, 2018

Unknown foundation susceptible to scour has been a longstanding problem threatening the safety of bridges. There are still about 28,000 highway bridges in United States with unknown foundations in 2016 according to the National Bridge Inventory records along with numerous other local bridges facing the same issue. Several methods have been developed over the years, including the sonic echo/ impulse response method, bending wave method, borehole methods and many extensions and modifications of these methods. The borehole methods are considered reliable but are expensive, and the surface based methods are inexpensive but lack the same level of reliability as borehole methods. Towards filling this gap, we developed a new surface based NDE method named Effective Dispersion Analysis of Reflections (EDAR) that is shown to be accurate and reliable. The method is based on accurately capturing the wave dispersion as it propagates through the pile, and applicable to both longitudinal and bending waves. Specifically, EDAR processes measured accelerations at two distinct locations on the pile due to hammer impact, resulting in an estimate of pile length, by examining the phase oscillations due to reflection as a function of wavenumber. Experimental validation of EDAR was conducted using side impact on concrete filled steel tubes, consistently resulting in less than 5% error in laboratory setting, and about 10% in field conditions. This talk would contain the formulation of underlying EDAR, verification with synthetic data, as well as details of laboratory and field validation.

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Delamination Detection in Concrete Bridge Decks Using Automated Acoustic Scanning System

Presenting author(s): Dr Hongbin Sun »

Co-Authors: Dr Jinying Zhu

Room: Regency Ballroom ABC | 3:25 PM Tuesday, August 28, 2018

Delamination is one of the most common problems in concrete bridge decks. Accurate evaluation of concrete bridge decks can help highway agencies make proper maintenance decisions and reduce repair cost. Traditional sounding method like impact echo (IE) is very time-consuming. Another sounding method, chain drag test is widely used for shallow delamination detection. However, the chain drag test replies on the subjective interpretation of operators and can not provide archivable data for future use. In this study, an automated acoustic scanning system is developed for rapid delamination detection in concrete bridge decks. A new ball-chain impact source is designed by combining the advantages of chain drag (rapid testing speed) and impact echo tests (analysis in frequency domain). Compared to the conventional chain drag test, the ball-chain results show better signal-to-noise ratio (S/N), higher sensitivity and repeatability to delamination identification. The automated scanning system includes excitation sources (ball-chains), acoustic sensors (microphones), positioning system (GPS), data acquisition (oscilloscope), and signal processing algorithm. Acoustic signals are recorded continuously in a streaming mode and processed by short-time Fourier transform (STFT) in the frequency range 0.5 kHz to 5 kHz. Acoustic scanning results are integrated with positioning data to generate an image of the scanned area in a map view. The system was validated in field test on concrete bridge decks in Omaha, Nebraska and shows satisfactory accuracy, efficiency, and repeatability.

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Fracture Monitoring of Ultra-High Performance Concrete (UHPC) Beam under Four-Point-Bending by Acoustic Emission

Presenting author(s): Mrs Ninel Alver

Co-Authors: Mr Sena Tayfur, Dr H Murat Tanarslan

Room: Garden State Ballroom | 3:25 PM Tuesday, August 28, 2018

Ultra High Performance Concrete (UHPC) is a cement-based composite material and has been widely used in such structural fields as bridges and harbors. The studies indicate that UHPC having far higher mechanical superiorities than conventional concrete, has high strength and energy absorption under bending. Moreover, because presence of steel fibers increase the shear capacity, UHPC has become attractive to be used for productions of beams where high load carrying capacity is needed with smaller dimensions. There are numerous techniques in order to monitor structural members subjected to loading. Acoustic Emission (AE) is one of these techniques and is a nondestructive testing method which is used for detection of damage under stress by detecting elastic waves. The method is effective for damage detection also in concrete. In this study, in order to monitor fracture development in a UHPC beam under four-point-bending, AE technique was applied. Thereafter, AE data obtained from the tests were analyzed by parameter-based and signal-based techniques. Consequently, fracture behavior of the UHPC beam was evaluated by comparing AE results with mechanical observations and effectiveness of AE method was revealed.

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Concrete Bridge Deck Assessments with Impact Echo for Bare Decks and Surface Waves Scanning for Asphalt Overlaid Decks and Asphalt Pavements

Presenting author(s): Mr Larry Olson

Co-Authors: Mr Patrick Miller

Room: Regency Ballroom ABC | 3:50 PM Tuesday, August 28, 2018

Larry D. Olson, PE and Patrick Miller, PE, Olson Engineering, Inc. Nondestructive Evaluation (NDE) methods are increasingly being used to assess the deteriorating conditions of ageing bridge superstructure and substructure due to long-term environmental and corrosion effects along with destructive coring/lab testing to map out damaged areas for repairs and to predict remaining service lives. Environmental aging factors of freeze-thaw, de-icing salts, sea salts, and atmospheric carbonation all lead to reduced concrete integrity and corrosion of bridge (and parking garage) deck reinforcement. The results of National Cooperative Highway Research Program sponsored research aimed at overcoming the limitations of acoustic sounding with chain dragging will be presented on the development of slow-rolling, scanning Impact Echo scanning technology for bare concrete decks to detect both top and bottom reinforcement delaminations as well as cracking damage, honeycomb and deck thicknesses. The basic Impact Echo scanning technology has been extended to include combined Impact Echo/Spectral Analyses of Surface Waves (IE/SASW) tests for detection of delaminations in asphalt overlaid bridge decks as well as delaminations between lifts of asphalt pavements. Case histories will be presented to illustrate the successful implementation of the IE/SASW scanning technologies on bridge deck assessment projects for accurate damage mapping and repair program development and on SHRP 2 R06D research on delamination of asphalt pavements. The use of these NDE methods along with the laboratory tests of concrete specimens allows for development of concrete deck repair programs and extended service life for bridges. Recent advancements in data processing will be presented for SASW on asphalt decks and pavements with delaminations along with coring results for ground-truthing comparisons.

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Correction of Acoustic Emission Parameters for Damage Detection in Concrete

Presenting author(s): Mrs Ninel Alver

Co-Authors: Mr Sena Tayfur

Room: Garden State Ballroom | 3:50 PM Tuesday, August 28, 2018

Acoustic Emission (AE) method is based on propagation, detection and analysis of elastic waves originated from failure within a stressed material. By this method, AE wave signals are obtained and locations, time of origins and progresses of the cracks in concrete even at low load levels can be determined by using their features. These AE waves are directly affected by material composition. If the material is attenuant and dispersive, the waves are deteriorated. While concrete exhibits heterogeneous and anisotropic behavior due to mixture of cement, aggregate, water and other admixtures, deterioration of the AE signal parameters becomes unavoidable in concrete. However, these parameters directly affect the results and evaluation of the damage state of concrete. Thus, accuracy of AE parameters is an important problem to be solved for heterogeneous materials. In this paper, with the purpose of correcting AE parameters for damage detection in concrete, loaded concrete specimens were monitored with AE and Parameter Correction Technique (PCT) was utilized. Afterwards, traditional and corrected AE parameters were analyzed and compared to each other. Results verify that this process has highly impressive contributions to estimation of the damages accurately rather than using raw data.

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Phase Analysis of Data from Air-Coupled Impact Echo Testing of Concrete Decks

Presenting author(s): Mrs Najjiya Almallah

Co-Authors: Mr Mahmoud Al-Quzwini, Dr Nenad Gucunski

Room: Regency Ballroom ABC | 4:15 PM Tuesday, August 28, 2018

Impact-echo is a nondestructive testing method used to detect internal defects, primarily delamination, in concrete elements. The amplitude spectrum is commonly used to determine the thickness frequency that gives information of the element thickness, or is an indication of the presence of a defect or anomaly. However, the amplitude spectrum is usually contaminated with multiple modes, and the localization of the thickness frequency is not straightforward. Furthermore, preprocessing is required to remove the unwanted wave components, and to eliminate or reduce noise. The phase spectrum of the impact echo signal contains information about the dispersion properties. Recently, these properties were used to determine the impact echo resonance frequency, which corresponds to the zero group velocity mode (S1-ZGV). This study examines the use of the phase spectrum of impact-echo signals, recorded from multiple air-coupled sensors, to locate internal defects in concrete elements. The phase spectrums of these signals are stacked together to obtain a 2D frequency-sensor offset profile. This profile shows a constant phase at the impact-echo thickness frequency. The performance of the method is successfully examined on decks with shallow and deep delamination, and without delamination. Furthermore, an algorithm is developed to automatically locate the frequencies corresponding to a constant phase, making the proposed method suitable for automated detection and characterization of delamination.

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Nondestructive Evaluation for a Concrete Bridge Using Coda Wave Interferometry

Presenting author(s): Dr Hanwan Jiang »

Co-Authors:

Room: Garden State Ballroom | 4:15 PM Tuesday, August 28, 2018

Nondestructive evaluation of concrete structures is an important task in the field of civil infrastructure. Unfortunately, the high inhomogeneity and heterogeneity in concrete materials complicate the detection and analysis processes, especially for weak stress and structure changes. In literature, coda wave experiencing multiple volumetric scattering shows promise for sensing weak changes in heterogeneous media such as concrete. Here, the nondestructive evaluation results are presented from the application of the coda wave interferometry (CWI) technique to a concrete beam. Specifically, we conducted the varied external loads on a concrete beam, and a couple of sensors worked as sources or receivers are installed sparsely to generate/collect the ultrasound wave signals at different positions. Then for each source-receiver pair, the CWI technique is utilized to quantify the coda waveform variations including stretches/compressions and distortions, which further indicate the stress changes and weak defects in the beam. The presented results may offer great practical applications for the nondestructive evaluation and testing (NDT) of concrete structures.

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Concrete Airfield Pavement Moduli Back Calculation

Presenting author(s): Dr Richard Ji

Co-Authors:

Room: Regency Ballroom ABC | 10:15 AM Wednesday, August 29, 2018

Nondestructive deflection testing has been accepted widely as a cost-effective tool for evaluating the structural condition of airfield pavements. Concrete elastic modulus and modulus of subgrade reaction of concrete pavement was back-calculated using HWD (Heavy Weight Deflectometer) deflections at the NAPTF test site. New methods for backcalculating parameters of concrete pavements is developed. In the proposed method, subgrade of concrete pavements is assumed as a liquid-dense foundation, An Finite Element Method (FEM) based plate theory in conjunction with optimization method shows that it can be more general in application, and it can provide an alternative and more versatile in considering concrete slab size and HWD testing locations compared to methods currently available.

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Overlay Effects on Corrosion Evaluation with Nondestructive Testing Methods for Concrete Bridge Decks

Presenting author(s): Dr Dewei Meng

Co-Authors: Mr Shibin Lin, Dr Hoda Azari

Room: Garden State Ballroom | 10:15 AM Wednesday, August 29, 2018

The use of deicing agents on concrete bridge decks will cause corrosion of steel reinforcement which may induce concrete deteriorations such as delamination and spalling. Overlays are employed for the deteriorated concrete decks to extend their service life. Tracking the corrosion condition in the decks after overlays being installed is meaningful for evaluating the effectiveness of the overlays and providing deck conditions continuously. Non-destructive testing (NDT) methods has been successfully used in corrosion evaluation for concrete bridge decks. However, the presence of overlays brings challenges to the NDT methods. In this study, three NDT methods were employed in laboratory tests of seven specimens to assess the effects of overlays on corrosion evaluation for the underlying concrete decks. The three NDT methods were electrical resistivity (ER), ground penetrating radar (GPR), and half-cell potential (HCP). The seven overlays are epoxy, latex modified concrete, silica fume modified concrete, polyester polymer, asphalt with a liquid membrane, asphalt with a sheet membrane, and asphalt without a membrane. The overlays rendered the ER method ineffective for corrosion evaluation for all seven specimens. The GPR method detected the concrete corrosion through the overlays for five specimens. Though the HCP method detected the decrease in electrical potential over the corroded reinforcement from all seven specimens, only two specimens could be identified to have active rebar corrosion per the ASTM C876-15 standard.

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Inversion of Air-Coupled Surface Wave Pavement Testing Data Based on Individual Receivers Spacing Approach

Presenting author(s): Mrs Hiba Al-Adhami »

Co-Authors: Dr Nenad Gucunski

Room: Regency Ballroom ABC | 10:40 AM Wednesday, August 29, 2018

Air-coupled SASW (spectral analysis of surface wave) testing is a seismic technique for in situ evaluation of elastic moduli and layer thickness of layered systems, such as pavements and soils. It is an improvement over the conventional SASW testing with ground-coupled sensors in a way that leaky surface waves are detected by non-contact (i.e. air-coupled or microphones) sensors. Commonly, the average of the dispersion curves for different receivers spacing is used in the inversion process. However, there may be significant differences in the dispersion curves for different spacing due to the interference of a number of body and surface waves radiated from the surface, and even direct acoustic waves. This study presents an inversion procedure for the air-coupled SASW testing on asphalt concrete (AC) pavements based on an individual receiver spacing approach. The inversion process itself is done using artificial neural networks (ANNs). The ANNs were trained by using several hundred synthetic dispersion curves for different receiver spacing developed from the numerical simulation of air-coupled SASW test. The inversion results of the recently developed ANNs models were compared with the models developed based on the average dispersion curves. The results point to significant improvements in the pavement modulus profile prediction.

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Effective Application of 3D-GPR System for Various Civil Engineering Tasks

Presenting author(s): Dr Aleksey Khamzin »

Co-Authors: Mr Kenneth Maser

Room: Garden State Ballroom | 10:40 AM Wednesday, August 29, 2018

As a part of Strategic Highway Research Program (SHRP2), a novel 3D-Radar system for a broad range of civil engineering tasks. A step-frequency array system was utilized as a primary inspection tool in a pilot projects for a wide range of applications, such as evaluation of bridge deck conditions, detection of stripping and delaminations, delineation of subsidence zones, pavement material thickness evaluation, grouting columns monitoring, evaluation of dowel bar alignment, etc. Collected data were used to develop post processing and data analysis procedures for effective analysis and evaluation of results. The research outcomes will be used to assess the effectiveness of the proposed equipment capabilities; explore the potential implementation of technique for routine testing; compare the 3D-Radar system performance to currently adopted NDT systems; identify areas needing improvement. The presentation encompasses a variety of performed engineering tasks, advantages of the utilized approach over using convenient testing methods, overall potential of the employed GPR system, and capabilities of software (3dr Examiner, ExploreGPR).

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Future Federal Aviation Administration (FAA) Developments of Roughness Evaluation for In-Service Airport Pavement

Presenting author(s): Mr Albert A Larkin »

Co-Authors:

Room: Regency Ballroom ABC | 11:05 AM Wednesday, August 29, 2018

Presentation Abstract Current available roughness indexes in ProFAA have been reviewed and statistically correlated with aircraft simulation results from the FAA’s Boeing B737 and Airbus A330 simulator projects at the Mike Monroney Aeronautical Center (MMAC) in Oklahoma City, OK. Relationships were determined between outputs from the simulator and current indices followed by developing linear or nonlinear correlation models. The outputs from the simulator were: pilot subjective roughness scenario ratings, simulator accelerometer measured responses, and pavement serviceability. These statistical models will be validated using the FAA owned Boeing 727 at the Atlantic City International Airport. The model validation will include using known gear geometry, aircraft weight, existing profiles, and aircraft speed. The Boeing 727 will be instrumented with a Distance Measuring Instrument and laser for vertical displacement and accelerometers on the main gear, nose gear, pilot seat, and center of gravity. The inertial profiles collected with the aircraft will also be compared to profiles collected with the FAA NDT van using the same inertial profiler system. In addition, improvements to the FAA longitudinal profile data collection and plotting program, ProFAA will be discussed. The enhancements include plotting the profiles using Global Positioning technology and displaying Boeing Bump Index values along the longitudinal profile, similar to Pavement Condition Index ‘at a glance’ capability in the FAA’s airport pavement management program, FAA PAVEAIR.

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Migration-based Automated Rebar Picking for Condition Assessment of Concrete Bridge Decks with Ground Penetrating Radar

Presenting author(s): Dr Kien Dinh »

Co-Authors: Dr Nenad Gucunski, Mr Trung Duong

Room: Garden State Ballroom | 11:05 AM Wednesday, August 29, 2018

Automatic identification and localization of rebar from ground penetrating radar (GPR) data has been a research topic of great interest. This paper presents an automated rebar picking algorithm for GPR data of concrete bridge decks. The algorithm is based on the Limited and Simplified Hyperbolic Summation (LSHS) technique in which the width of migration is limited and a counter is used to check if a hyperbolic signature exist in a sub-region of GPR image. More specifically, after a time-zero correction, each pixel in the raw GPR image with a positive amplitude will be migrated, as it is usually done with the conventional hyperbolic summation (HS) technique. However, for each pixel to be migrated, the width of migration is limited in the horizontal direction and a unit value will be used for migration, instead of the true amplitude values of the pixels. In the obtained image, the pixels containing rebar peaks will normally have the intensity values close to the number of pixels corresponding to the width of migration and, therefore, can be picked. Whereas the method is rather straightforward and simple to develop, its implementation on GPR data of two concrete bridge decks has shown good results. First, the GPR condition maps obtained from the proposed algorithm are in a good agreement with those developed by the manual method of rebar picking. Second, the accuracy of the picking algorithm was 98.09% and 99.21% for the two decks, respectively.

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Evaluation of Pavement Performance under FWD Test through Instrumented Pavement Section

Presenting author(s): Mr Zafrul Khan

Co-Authors: Mr Rafiqul Tarefder

Room: Regency Ballroom ABC | 11:30 AM Wednesday, August 29, 2018

This study shows the variation in pavement performance through instrumented pavement section under different climatic conditions. A section on Interstate 40 (I-40), near Albuquerque, New Mexico, USA, has been instrumented with 32 sensors including strain gauges, pressure plates, moisture probes, temperature probes, axle sensing strips, weather station and Weigh-in-Motion (WIM). Data from the sensors are being collected continuously. Routine FWD (Falling Weight Deflectometer) test is being conducted on the exact same position of the pavement. FWD test data from 2015 to 2017 was used to observe the changes the pavement performance. Strain at the bottom of AC layer and stress at base, subbase and subgrade layer under FWD 9-kip load were also studied. During this time, pavement temperature varied from -1°C to 39°C. Field obtained asphalt concrete (AC) modulus were corrected for temperature variation to a reference temperature of 21°C. From the FWD modulus for AC layer, it was observed that at January 2015 modulus was 9400 MPa, and on November 2017 the modulus value was 3800 MPa. Damage value for AC layer was calculated using the field FWD backcalculated AC modulus value and undamaged AC modulus. The undamaged AC modulus was obtained from the dynamic modulus test conducted at 21°C. From the results, it was observed that from January 2015 to November 2017, AC layer damage increased by 6%.

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Detection of Buried Trolley Tracks Using Multichannel 3D Ground Penetrating Radar Technology

Presenting author(s): Mr Manuel Celaya »

Co-Authors: Mr Khosrow Tabrizi, Mr Michael Frabizzio, Mr Omar Hameed

Room: Garden State Ballroom | 11:30 AM Wednesday, August 29, 2018

Abandoned railroad or trolley tracks can be a troublesome problem for transportation engineers. On many occasions these linear features are paved over time and records are non-existent, inaccurate or difficult to find. Sometimes, abandoned tracks are found when resurfacing or rehabilitation operations are conducted on existing roads, causing costly project overruns and construction delays. In this study, a section of a municipal road in New Jersey was investigated to identify buried trolley tracks and determine the thickness of asphalt over these tracks. Trolley tracks were known to have existed within the project limits many years ago and been subsequently overlaid with asphalt. However, the exact location, extent and asphalt overlay thickness were unknown. To shed light on these unknowns, non-destructive Ground Penetrating Radar (GPR) testing was employed. The GPR survey was conducted using two ground-coupled (G.C.) GPR systems, a single antenna retrofitted to a push-cart vehicle and a high-density, multi-channel trailer system. In addition to GPR, a limited coring program was carried out to verify and calibrate the GPR findings. Based on the GPR findings, two sets of trolley tracks were found within the project limits. Core data was used to calibrate the GPR findings and determine the asphalt thickness over the tracks. All findings were combined into a Microstation file with the New Jersey State Plane Coordinate system as a reference and overlaid on existing as-builts. In addition, a georeferenced Google Earth file (kml format) was prepared separately for easy reference.

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Augmented Reality to Enable the Next Generation of Infrastructure Inspection

Presenting author(s): Mr David Mascarenas

Co-Authors:

Room: Regency Ballroom ABC | 1:00 PM Wednesday, August 29, 2018

In this work we present a summary of our current research into the use of emerging augmented reality technologies to aid in the documentation of infrastructure inspection. It is becoming increasingly recognized that the 50 year service life previously used to design infrastructure is not sufficient. Engineers are increasing considering techniques to design infrastructure that will last 100 + years. Infrastructure with such long lifespans will introduce new challenges for civil engineers responsible for the maintenance of this infrastructure. Conventional infrastructure inspection techniques involve making measurements with tape measures, filling out forms to document damage and repairs, the use of GPS to geolocate damage, and the use of chain drags to listen for damaged areas in bridge decks. The problem with these techniques is that they tend to result in only very sparse information about the state of the infrastructure. Furthermore, even language and culture may change on the timescale of 100s of years, and as a result, hand-written notes may become ambiguous and difficult to understand. Emerging augmented reality tools offer a possible solution to mitigate these challenges. Contemporary augmented reality headsets feature conventional imagers as well as depth imagers that can be used to quickly and easily capture unambiguous, high-resolution, full-field 3D measurements of infrastructure. These measurements could be used to provide highly detailed geometrical information regarding the state of infrastructure at the time of inspection. These measurements could also be used to generate finite element models that accurately reflect the geometric condition of the infrastructure at a given point in time. Augmented reality also opens up the possibility of facilitating sharing of infrastructure inspection notes between inspectors across time because it opens up the possibility for including geotagged notes that we created by various inspectors. Even though augmented reality is only beginning to become commercially available, it is already presenting infrastructure inspection researchers with exciting possibilities for tools that can be used to perform the next generation of infrastructure inspection. 

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Field Validation of Multipurpose Wireless Sensors for Bridge Assessment

Presenting author(s): Mr Mustafa Furkan »

Co-Authors: Mr Qiang Mao, Mr Stylianos Livadiotis, Mr Matteo Mazzotti, Dr A Emin Aktan, Mr Charles Young, Dr Ivan Bartoli, Mr Paul Sumitro, Mr Fred Faridazar

Room: Garden State Ballroom | 1:00 PM Wednesday, August 29, 2018

Use of wireless sensors for Structural Health Monitoring (SHM) has been considered by many researchers. Wireless sensors have emerged as a promising technology since their installation is fast and they can reduce monitoring costs. However, power management, uncertainty in wireless connectivity, and data quality issues are some of the reported disadvantages in addition to common sensing issues such as ruggedness that is needed for field applications. In this paper, a suite of recently developed wireless sensors that were developed from existing, proven and robust wired sensors is presented. The developed wireless sensing units were tested in the field on an operating 11 span viaduct to assess the potential for their implementation within a wireless based Structural Assessment framework for bridges and other structures. The performance of the proposed wireless sensors was mostly very promising. This study was funded by a Federal Highway Administration project that aims to ultimately present a wireless sensing system that can be implemented for both rapid structural bridge assessment as well as long-term SHM.

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Mixed Reality Assisted Infrastructure Assessment

Presenting author(s): Mr Enes Karaaslan

Co-Authors: Mr Kevin Pfeil, Dr Fikret Necati Catbas, Mr Joseph LaViola

Room: Regency Ballroom ABC | 1:25 PM Wednesday, August 29, 2018

Conventional methods for visual assessment of civil infrastructures have certain limitations, such as subjectivity of the collected data, long inspection time, and high cost of labor. Although some new technologies (i.e. robotic techniques) that are currently in practice can collect objective, quantified data, the inspector’s own expertise is still critical in many instances; because these technologies are designed to replace human expertise, or are ineffective in terms of saving time and labor. By developing a Mixed Reality (MR) framework which can be integrated into a wearable holographic headset device, a bridge inspector, for example, can analyze a certain crack that he or she sees on a pier, display its dimension information along with the condition state, and can even communicate through the headset with the central office if further assistance is required. If there is a hard to reach location, there will not be a need for additional access equipment such as a ladder or snooper truck. The headset can zoom in to the damage location or connect to an unmanned aerial system (UAS) to capture the damage. This study explains a methodology for the described system in which a mixed reality headset is customized to integrate a Computer Vision (CV) and Artificial Intelligence (AI) based framework. The resulting system from this research will be adopted by civil infrastructure inspectors to analyze real-time images taken from an infrastructure and display analysis results along with condition assessment on the headset interface. Thereby, the inspector and the AI framework will collaborate/communicate for improved visual inspection. This system will accelerate certain tasks of the inspector such as detection, measurement, and assessment of defects through AI automation; therefore offers significant contributions to infrastructure inspection, maintenance, management practice, and safety for the entire Departments of Transportation in the US as well as other countries.

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Wireless Remote Sensing Projects Funded by the FHWA Exploratory Advanced Research (EAR) Program

Presenting author(s): Mr Bruce V Johnson

Co-Authors:

Room: Garden State Ballroom | 1:25 PM Wednesday, August 29, 2018

FHWA has a unique program to investigate and help develop new and innovative monitoring and investigation systems for transportation. It is called the Exploratory Advanced Research (EAR) Program and it addresses the need to conduct research on longer term and higher risk breakthrough research with the potential for transformational improvements to plan, build, renew, and operate safe, congestion free, and environmentally sound transportation systems. The program is also unique in that it engages stakeholders to evaluate potential research topics and to assist in communicating the research results. FHWA identifies and scopes topics through extensive initial-stage investigation. FHWA uses expert panels to ensure the technical quality of sponsored research. The panels are composed of Federal, State, academic, and international scientific and engineering experts, who are vetted to avoid conflicts of interest. FHWA is committed to transitioning the results of EAR Program-funded research projects and takes an active role in demonstrating results to audiences critical to continuing the research and development cycle. One such project was to develop a market ready self-powered structural health monitoring system. The system operation was demonstrated on the I-75 Mackinac Bridge in Michigan. The project demonstrated the feasibility of installing self-powered piezo-floating-gate sensors for detection and monitoring of fatigue cracks in structural steel plates in a severe environment. The sensor development, installation, data collection and data analysis will be described. Findings of the project and dissemination of results will be described to illustrate the value and significance of the work done under the FWHA EAR program.

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Towards Data Based Corrosion Analysis of Concrete with Supervised Machine Learning

Presenting author(s): Dr Ernst Niederleithinger

Co-Authors: Dr Christoph Volker, Ms Sabine Kruschwitz, Mr Gino Ebell

Room: Regency Ballroom ABC | 1:50 PM Wednesday, August 29, 2018

Half-Cell-Potential Mapping (HP) is the most popular non-destructive testing (NDT) method for the detection of active corrosion in reinforced concrete. HP is influenced by parameters such as moisture and chloride gradients in the component. The sensitivity to the spatially small, but dangerous pitting is low. In this study we show how additional measurement information can be used with multi-sensor data fusion to improve the detection performance and to automate data evaluation. The fusion is based on supervised machine learning (SML). SML are methods that recognize relationships in (sensor) data based on given labels. We use SML to distinguish "defective" and "intact" labeled areas in our dataset. It consists of 18 measurement - each contains HP, ground radar, microwave moisture and Wenner resistivity data. Exact labels for changing environmental conditions were determined in a laboratory study on a reinforced concrete slab, which deteriorated controlled and accelerated. The deterioration progress was monitored continuously and corrosion was generated targeted at a predefined location. The detection results are quantified and statistically evaluated. The data fusion shows a significant improvement over the best single method (HP). We describe the challenges of data-driven approaches in nondestructive testing and show possible solutions.

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Toward Autonomous Self-Powered Self-Sensing Civil Infrastructure

Presenting author(s): Mr Nizar Lajnef

Co-Authors: Mr Hassene Hasni, Mr Kenji Anno, Mr Shantanu Chakrabartty, Mr Fred Faridazar

Room: Garden State Ballroom | 1:50 PM Wednesday, August 29, 2018

The next generation Smart Cities will be heavily dependent on distributed smart sensing systems to monitor the urban infrastructure. One of the main challenges in structural health monitoring (SHM) is to find a reliable and suitable source that can continuously power the sensors during the whole life span of the built structural system (typically few decades). Traditional health monitoring systems rely on batteries which have a very limited lifetime, thus requiring frequent replacements. This is impractical and would considerably increase maintenance cost. In this paper, we highlight the progress of our work funded through the FHWA’s Exploratory Advanced Research program. This work led to the development of a battery-free, wireless multi-metric sensing system for the continuous and autonomous monitoring of bridge components. The sensor operates by harvesting mechanical energy from structures using piezoelectric transducers. The performance of this technology is benchmarked for different civil infrastructure systems subject to a multitude of damage scenarios. The developed models integrate finite element (FE), experimental testing, and statistical and artificial intelligence (AI) approaches. Sensors fusion models are also developed to increase the accuracy of the damage sensing system. In addition, a case study of the deployment of a network of sensors on the Mackinac Bridge in Michigan is presented.

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Full-Depth Assessment of Concrete Bridge Decks in A GPR Survey: A Machine Learning Approach

Presenting author(s): Dr Arezoo Imani

Co-Authors: Mr Shahin Saadati, Dr Nenad Gucunski

Room: Regency Ballroom ABC | 2:15 PM Wednesday, August 29, 2018

The current practice for condition evaluation of bridge decks using GPR does not provide a full depth assessment of the deck and is limited only to the portion of the deck above the top reinforcement mat. Additionally, there are ambiguities and uncertainties associated with the GPR data interpretation especially when it comes to differentiating the concrete material condition. The amplitude or the shape of the hyperbola of reflection from rebars in the B-scan do not provide sufficient information regarding the material condition. A series of FDTD simulations were conducted to expand the GPR evaluation zone beyond the top reinforcement level, and to provide a full depth assessment of the deck. The slab was divided into three separate yet interconnected longitudinal layers. A parametric study was performed by changing the properties of each concrete layer. The quality of concrete was characterized by two electromagnetic properties – permittivity and conductivity. Using the electromagnetic properties as characteristic parameters, six concrete conditions from good to critical were simulated. A machine learning technique called gradient boosting was used to predict the layers’ condition. The amplitudes at the top and bottom reinforcing layer, and at the bottom of the slab, as well as the travel times were used as the model input features. The paper presents the study of the influence of each feature on the prediction of layer properties.

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Evaluating Robustness of Fatigue Crack Monitoring Using Carbon Nanotube-Based Sensor

Presenting author(s): Dr Shafique Ahmed

Co-Authors: Dr Erik T Thostenson, Dr Thomas Schumacher, Dr Jennifer R McConnell

Room: Regency Ballroom DEF | 2:15 PM Wednesday, August 29, 2018

Throughout the United States, many fatigue cracks have already been detected in steel bridges and it has been predicted that the majority of existing steel bridges have fatigue-prone details. These bridges are vulnerable to fatigue damage. Because they experience millions of loading cycles per year and cyclic loading can nucleate and propagate fatigue crack and eventually, the damage can trigger catastrophic failure. Conventional repair techniques (e.g., crack-stop holes, adding bolted steel plates) often fail to arrest the crack. Thus, monitoring structural members vulnerable to fatigue is critically important. Most of the commercially available sensors (e.g., crack propagation gage, electrochemical fatigue sensor) cannot be effectively integrated with conventional repair schemes and they work as point sensors. In this work, response of a carbon nanotube (CNT)-based distributed sensor consisting of a nerve-like network has been evaluated for monitoring fatigue damage. To evaluate the sensor response for monitoring crack propagation and stability under near-threshold crack propagation conditions, fatigue tests were conducted under various amplitude cyclic loading. A crack-stop hole repaired metal specimen was tested to evaluate the sensor response for detecting crack re-initiation. Experimental tests show that the CNT-based distributed sensor can effectively monitor fatigue crack propagation and detect re-initiation from a repair schemes and the sensor response is stable under near-threshold crack propagation conditions. In addition, this sensor can be embedded in an adhesive bondline of composite/steel repair scheme and thus, repair and monitoring can be effectively integrated.

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Impact-Echo Data Processing, Visualization and Interpretation Including Machine Learning Concepts

Presenting author(s): Mr Daniel Algernon

Co-Authors: Mr Sascha Feistkorn, Mr Michael Scherrer

Room: Regency Ballroom ABC | 2:40 PM Wednesday, August 29, 2018

While impact-echo has a long tradition in Nondestructive Testing in Civil Engineering (NDT-CE) already, there is constant development regarding scanning data collection process, types of transducers, the data processing and visualization as well as the correct interpretation of the results. More than for many of the other methods in NDT-CE, the physical principle of impact-echo echo allows a fast data acquisition process, which along with reasonable equipment cost makes the method highly efficient. Impact-echo is an elastic method based on the use of elastic stress waves generated by an elastic impact and the analysis of the frequency spectrum. Based on the physics involved, it is sensitive for delamination and discontinuities related to changes in elastic properties and the respective interfaces. Common applications are thickness measurements, the detection of delaminated or honeycombed areas as well as the inspection of the grout in metallic tendon ducts. While the data interpretation has been generally considered rather complex, the large amount of information included in the impact-echo data gives it great potential if extracted intelligently. Numerous processing methods have been applied to extract the relevant information. Also there are powerful visualization techniques providing vivid and intuitive representations of the results. Further advancements regarding the correct interpretation of the results are currently achieved by the introduction of machine learning concepts to impact-echo. The implementation in software tools makes the technology accessible to an increasing range of practitioners.

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Contract Development for Instrumentation and Monitoring of Bridges

Presenting author(s): Ms Patricia L Kiehl

Co-Authors: Mr Tom Macioce

Room: Garden State Ballroom | 2:40 PM Wednesday, August 29, 2018

Bridge instrumentation and monitoring is a mature technology that has been used by many states. In general, the use has been limited to a single bridge to determine the performance. The use of bridge instrumentation on multiple bridges spread throughout a state has not been used frequently. The development of an advertisement and contract to perform instrumentation and monitoring on various bridges to ascertain selected performance has not been well documented. The process for selecting bridges, determining necessary instrumentation locations and instrumentation durations will be discussed. The development of a request for proposal and contract language will be discussed as it relates to the objective of the instrumentation program.

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Phased Array Ultrasonic Testing of Cast Steel Sluice Gates

Presenting author(s): Mr Carl D Leunig

Co-Authors:

Room: Regency Ballroom ABC | 3:25 PM Wednesday, August 29, 2018

The U.S. Army Corps of Engineers (COE) has a vast inventory of hydraulic steel structures (HSS) as part of the many dam projects it operates and maintains. HSS are required to be routinely inspected and HSS with fracture critical members are required to have an in-depth inspection at least once during their lifespan which includes non-destructive testing (NDT) in addition to visual inspection. Many HSS throughout the COE inventory have no documentation of an in-depth inspection. The sluice gates at a typical dam are inherently difficult and costly to remove from service in order to adequately perform an in-depth inspection. The sluice gates at Francis E. Walter Dam (FEW) have a fracture critical cast steel gate leaf with an upstream and downstream skin plate and internal stiffening members cast as one piece. This complex geometry facilitates the need for NDT in the form of Phased Array Ultrasonic Testing (PAUT). PAUT is the only NDT method available for efficiently and accurately inspecting a cast steel sluice gate. The use of PAUT on a cast steel sluice gate was proven to be feasible in a test study on one of the gates at FEW. The testing was able to be performed without removing the gate from service and was able to accurately identify and measure several features of the gate leaf geometry. There are still steps that need to be taken to refine the procedure for inspecting cast steel sluice gates with PAUT. Regardless, the ability to perform an in-depth inspection using PAUT on a cast steel sluice gate without having to first remove the gate from service provides cost savings, and also does not impact the normal operation of the dam.

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The Effectiveness of Ultrasonic Peening Improvement Treatment in Maintenance and Repair of Bridges

Presenting author(s): Dr Jacob Kleiman

Co-Authors: Mr Yuri Kudryavtsev

Room: Garden State Ballroom | 3:25 PM Wednesday, August 29, 2018

The ultrasonic impact treatment (UIT) is one of the new and promising processes for residual stress relief and fatigue life improvement of welded elements and structures. In most industrial applications this process is also known as ultrasonic peening (UP). The beneficial effect of UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of materials, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. The fatigue testing of welded specimens convincingly confirmed that UP is the most efficient improvement treatment when compared with such traditional techniques as grinding, TIG-dressing, heat treatment, hammer peening, shot peening and application of LTT electrodes. This paper presents an overview of results of a few studies conducted to evaluate the efficiency of Ultrasonic Peening in maintenance and repair of samples comprising bridge welded structural elements as well as discussing examples of use of the UP technology on actual bridges The results of the fatigue testing showed that UP provides significant fatigue improvement of welded elements, with the fatigue life of welded samples increasing after application of UP 4-5 times depending on the level of applied stresses.

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Innovations in Phased Array Ultrasound: Full Matrix Capture and the Total Focusing Method

Presenting author(s): Mr Alan Caulder »

Co-Authors: Mr Gavin Dao

Room: Regency Ballroom ABC | 3:50 PM Wednesday, August 29, 2018

Full Matrix Capture (FMC) and the Total Focusing Method (TFM) are revolutionizing phased array ultrasound. FMC and TFM are advanced acquisition and post-processing techniques, respectively, and can be implemented real-time for inspection purposes. FMC/TFM provides many benefits over conventional Phased Array, with unique features, such as: a real-time high resolution reconstruction grid, viewing of several wave modes from one setup, improved vertical and lateral resolution, higher signal to noise ratio, improved flaw characterization and sizing, and reduced misinterpretation of geometric echoes versus defects. Raw FMC data can be saved to be reprocessed later with improved signal processing algorithms. This paper will present a fundamental detailing of FMC/TFM, a sampling of TFM images from real-world defects, as well as highlighting improvements to speed up and optimize both FMC and TFM while keeping, and in some cases, improving signal-to-noise ratio. We also address the variable inputs to a system that can have a great overall effect on the FMC/TFM inspection and data quality. Although FMC requires large amounts of raw data to compute a TFM image, the instrument used for the experiments has more than enough data transfer capability at greater than 160 MB/s. Furthermore, with the acquisition instrument’s small form factor, advanced high resolution imaging capabilities that were once only lab capable can now be industrialized and even automated using scanners and robots.

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Inferring Dynamic Characteristics of a Bridge through Numerical Simulation and Low-Magnitude Shaking as a Global NDE Method

Presenting author(s): Mr Sharef Farrag »

Co-Authors: Dr Nenad Gucunski, Mr Franklin Moon, Mr John DeVitis

Room: Garden State Ballroom | 3:50 PM Wednesday, August 29, 2018

Boundary conditions of a structure affect its response to dynamic excitations. In most highway bridge designs, the dynamic soil-structure interaction is not considered, with an underlying assumption that bridge piers have fixed-ends. Foundation flexibility, and more importantly radiation damping from the foundation, whether it is a shallow or deep foundation, can significantly influence the response of substructure/superstructure system. This may lead to deviations of the actual response compared to the design assumptions, depending on soil properties and geometrical and structural characteristics of the bridge. Low-magnitude shaking can be used as the means of evaluation of actual dynamic characteristics of a bridge. Moreover, numerical simulations of the same bridge with the same low-magnitude shaking load on the bridge can be used to model the dynamic response of the bridge, with the consideration of the dynamic soils structure interaction. In this paper, a comparison between the actual response of a bridge in Hamilton Township, New Jersey, and results from numerical simulations is presented. The shaking of the bridge was done using T-Rex, a large mobile shaker from NHERI Experimental Facility at University of Texas at Austin. The test setup, and results from both numerical simulations and field-testing are presented and discussed.

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Nondestructive Investigation of Damage in a Composite Concrete-Steel Bridge Induced by Heat-Straightening Repair

Presenting author(s): Mr Jinesh K Mehta

Co-Authors: Mr Divyesh Vora, Mr Jason Gramlick, Mr Allen King

Room: Regency Ballroom ABC | 4:15 PM Wednesday, August 29, 2018

A routine inspection of a multi-span composite steel-concrete plate girder bridge on a Interstate 5 Freeway over-crossing in Los Angeles, CA discovered an impact load damage on the tension flange of one of the girders. The bottom flange of the entire girder was approximately offset by more than 2-in from horizontal and no cracks were observed at the point of impact. The damaged girder was later repaired using heat-straightening procedure. During the post-inspection heat-straightening repair, an approximate 20-ft long crack was observed on the soffit of the concrete bridge deck overhang. The Caltrans Office of Structural Materials (OSM) performed an investigation to determine the extent of the cracks and delamination of concrete on the bridge deck, and provide an assessment of the heat affected area of the steel girder from the heat-straightening repair. The bridge deck and soffit were subjected to an initial visual inspection to identify spall areas, cracks, and the overall condition. The initial visual examination was complemented with a borescope investigation of the concrete on the cracked areas of bridge deck. To supplement the investigation, non-destructive testing (NDT) with impact echo (IE) and ground penetrating radar (GPR) were also performed to evaluate the condition of the concrete bridge deck. The condition of the steel girder after the heat-straightening repair was assessed by performing hardness testing to evaluate the material properties on the heat-affected area and unaffected base metal, and magnetic particle testing to determine the presence of micro-cracks developed during the heat-straightening repair operations.

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An Innovative Methodology for Integrated Structural Health Monitoring and Rehabilitation of Concrete Structures Using Carbon Nanotube-Based Hybrid Composites

Presenting author(s): Dr Hongbo Dai

Co-Authors: Dr Thomas Schumacher, Dr Erik T Thostenson

Room: Garden State Ballroom | 4:15 PM Wednesday, August 29, 2018

This experimental study focuses on the development of an innovative hybrid composite system for integrated structural health monitoring (SHM) and rehabilitation of concrete structures. The central concept is that carbon nanotubes (CNT) are selectively coated onto a non-structural and scalable fabric to form a piezoresistive network that offers areal coverage, high sensitivity, and distributed sensing capabilities to monitor changes in strain and damage. The CNT-modified fabric is integrated with glass fiber reinforcement to create a combined strengthening and sensing solution. Strains and degradation in form of cracking have been found to directly cause an overall electrical resistance change measured between electrodes attached to the sensing layer. Furthermore, by employing a multiplexing approach using multiple electrodes, damage locations can be estimated spatially. In this presentation we discuss the basic principle of our methodology and the application on two large-scale reinforced concrete laboratory beams (12 in × 24 in × 16 ft), which were pre-cracked and then rehabilitated using the proposed approach. The first beam, which was designed to fail in flexure, was rehabilitated with a 14-ft-long and 12-in-wide composite patch on the tension face to increase its flexural strength; the second beam, which was designed to fail in shear on one side, was strengthened at its weaker side with three U-wraps. Both beams had integrated CNT sensors are were tested to failure. Real-time resistance measurements were collected during the entire loading protocol and compared with member deformations in form of strains and mid-span displacement and the outputs of two acoustic emission sensors.

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Challenges with Electromagnetics Based Nondestructive Stress Assessment in Existing Steel Bridge Structures

Presenting author(s): Dr Christian Boller »

Co-Authors: Mr Haoran Wu, Mr Peter Starke, Mr Eckhardt Schneider, Mr Wolfgang Kurz, Mr Christian Fox, Mr Markus Doktor, Ms Claudia Redenbach

Room: Regency Ballroom ABC | 4:40 PM Wednesday, August 29, 2018

Civil infrastructure such as bridges is usually designed to last for a long period of time. During such a period loading conditions may change, material may deteriorate and records may unexpectedly get lost. Means to allow real operational conditions of such an infrastructure to be determined may therefore be in need. Design of civil infrastructure is principally based on stress analysis due to the mainly linear elastic stress-strain behaviour. From non-destructive testing (NDT) in metallic materials it is known that besides flaw detection also material properties as well as stress conditions can be measured. This includes yield and tensile strength on the basis of electromagnetic properties such as coercivity, remanence, permeability, Barkhausen noise or a distortion factor, or ultrasound being generated electromagnetically in the structure to be analysed in the case of ferromagnetic materials by taking advantage of the acousto-elastic effect. Application of the respective electromagnetic techniques has been proven with success in a variety of metallic components in the past, however, mainly in the context of high performance steels used in mechanical engineering applications. However, with steels conventionally applied in civil engineering the purity and hence quality is comparatively low. This leads to a challenge with regard to the materials’ data recorded and the way on how to get them processed in the end. Along a study performed recently on a variety of civil engineering structural steels magnetic and ultrasonic properties have been recorded under different magnetisation and loading conditions and subsequently processed. It has been found that although the specimens had been fully magnetised the data recorded still scattered significantly. This scatter has been specifically attributed to a comparatively huge scatter in the materials’ properties making it still difficult to determine a sufficiently acceptable figure with respect to the stresses being applied. A way on how to get around the problem is to better understand the correlation between the materials’ microstructure on the one side versus the electromagnetic properties on the other and to explore which impact the number of measurements to be taken may have in conjunction with statistical aspects including the procedures to be applied on such a statistical evaluation, satisfying stress and loading figures to be obtained in the end.

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Detection of Delaminations in Concrete Bridge Decks Using Non-Linear Vibration Characteristics

Presenting author(s): Mr Ali Hafiz

Co-Authors: Dr Thomas Schumacher

Room: Garden State Ballroom | 4:40 PM Wednesday, August 29, 2018

A number of non-destructive evaluation (NDE) methods have been developed in the recent decades to detect delaminations in concrete bridge decks. Some of these methods, namely visual inspection, ultrasonic testing, impact echo, and impulse response can be used to detect and locate delaminations. Since the early 1970s, researchers have also investigated using the dynamic response properties of a structure, which is generally referred to as the vibration-based method. For damage detection, the vibration-based method requires a comparison with baseline data, which is not available in most cases. Generally, the vibration response due to an impact force can be measured by using accelerometers. The frequency response function (FRF) is then used to convert the response to the frequency domain. For an undamaged deck, varying the impact force does not affect the corresponding FRFs for frequencies that lie within the accelerometer’s operating range. On the other hand, the FRFs of a delaminated slab changes when the impact force is increased with the delamination causing a non-linear vibration response. In this paper, we present a new baseline-free method to detect damage in concrete slabs using the non-linear vibration characteristics. The method was employed on a severely deteriorated bridge, which consisted of 6 separate slabs. Three select slabs were tested on a 2 x 2 ft grid, and for each point in the grid, several impacts with varying magnitudes were applied. Subsequently, ultra-high-pressure hydro-blasting was performed on the deck for rehabilitation, which provided an opportunity to compare results.

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