Francisco A. Romero

Nondestructive Testing to Identify Concrete Bridge Deck Deterioration

This work was sponsored by the Federal Highway Administration in cooperation with the American Association of State Highway and Transportation Officials. It was conducted in the second Strategic Highway Research Program (SHRP 2), which is administered by the Transportation Research Board of the National Academies. The project was managed by Monica Starnes, Senior Program Officer for SHRP 2 Renewal. The research reported herein was performed by the Center for Advanced Infrastructure and Transportation (CAIT) at Rutgers University (RU); the Center for Transportation Infrastructure Systems (CTIS) at The University of Texas at El Paso (UTEP); the Federal Institute for Materials Research and Testing (BAM), Germany; and Radar Systems International, Inc. (RSI). Rutgers University was the coordinator and contractor for this project. Dr. Nenad Gucunski, professor and chair of Civil and Environmental Engineering and director of CAIT’s Infrastructure Condition Monitoring Program at RU, was the principal investigator. The other authors of this report are Dr. Soheil Nazarian, professor of Civil Engineering and director of CTIS at UTEP; Dr. Deren Yuan, research associate at CTIS at UTEP; Dr. Herbert Wiggenhauser, head of Non-Destructive Testing (NDT) in Civil Engineering at BAM; Dr. Alexander Taffe, leader of Combination and Automation of NDT of Buildings at BAM; Dr. Parisa Shokouhi, Alexander von Humboldt Research Fellow, hosted by BAM; and Doria Kutrubes, president of RSI. Arezoo Imani and Touraj Tayebi, graduate research assistants at RU, helped conduct the validation testing, data analysis, and web manual content preparation. Hoda Azari, a graduate research assistant, and Dr. Manuel Celaya, a research engineer at UTEP, assisted in the validation study as well. Hooman Parvardeh, research assistant at RU, helped build the reference database and develop the framework for the web manual, while Erica Erlanger, a research staff member at RU, edited the manuscript. Their contributions are gratefully acknowledged. The research team also gratefully acknowledges contributions of the participants from industry and academia in the validation testing. The participants include NDT Corporation; Germann Instruments; Olson Engineering; Dr. Ralf Arndt, National Research Council associate at FHWA Turner–Fairbank Highway Research Center; Ingegneria Dei Sistemi S.p.A. (IDS), Italy; 3D-RADAR, Norway; Dr. John Popovics, University of Illinois at Urbana-Champaign; Dr. Jinying Zhu, The University of Texas at Austin; Rutgers University—Center for Advanced Infrastructure and Transportation; and The University of Texas at El Paso—Center for Transportation Infrastructure Systems. The contributions of these participants were critical for the evaluation and grading of the performance of NDT technologies.

Mechatronic Systems Design for an Autonomous Robotic System for High-Efficiency Bridge Deck Inspection and Evaluation

The condition of bridges is critical for the safety of the traveling public. Bridges deteriorate with time as a result of material aging, excessive loading, environmental effects, and inadequate maintenance. The current practice of nondestructive evaluation (NDE) of bridge decks cannot meet the increasing demands for highly efficient, cost-effective, and safety-guaranteed inspection and evaluation. In this paper, a mechatronic systems design for an autonomous robotic system for highly efficient bridge deck inspection and evaluation is presented. An autonomous holonomic mobile robot is used as a platform to carry various NDE sensing systems for simultaneous and fast data collection. The robots NDE sensor suite includes ground penetrating radar arrays, acoustic/seismic arrays, electrical resistivity sensors, and video cameras. Besides the NDE sensors, the robot is also equipped with various onboard navigation sensors such as global positioning system (GPS), inertial measurement units (IMU), laser scanner, etc. An integration scheme is presented to fuse the measurements from the GPS, the IMU and the wheel encoders for high-accuracy robot localization. The performance of the robotic NDE system development is demonstrated through extensive testing experiments and field deployments.

Multiple Complementary Nondestructive Evaluation Technologies for Condition Assessment of Concrete Bridge Decks

Reinforced concrete bridge decks are exposed to several types of deterioration processes: corrosion, alkali–silica reaction, carbonation, shrinkage, freeze–thaw actions, and so forth. The most commonly found problem is corrosion-induced bridge deck delamination. Previous studies have shown that surveys of bridges relying on a single nondestructive evaluation (NDE) technology provide limited information about the condition of concrete bridge decks. To overcome limitations of individual technologies, a complementary approach using several NDE technologies should be used in bridge deck evaluation. The presented approach utilizes a suite of NDE technologies, namely, impact echo (IE), ultrasonic surface waves (USW), ground-penetrating radar (GPR), half-cell potential (HCP), and electrical resistivity (ER). The suite of NDE technologies was implemented in the evaluation of bridge decks on nine bridges in Iowa. The NDE was complemented by ground-truth measurements on the cores extracted from all nine bridge decks. Condition assessment with the five NDE technologies has clearly shown their advantages and limitations. For example, the GPR surveys provided assessment of concrete deterioration at relatively high speeds of data collection. In contrast, IE provided high accuracy in detection and characterization of delaminations in the deck but at a lower testing speed. HCP and ER tests provided assessment of the likelihood of corrosion, whereas the USW test provided accurate assessment of the effects of deterioration processes and defects on mechanical properties, primarily the degradation of the elastic modulus. Most important, the survey showed the advantages of use of multimodal NDE surveys in the comprehensiveness of condition assessment of concrete bridge decks.

Autonomous robotic system for high-efficiency non-destructive bridge deck inspection and evaluation

Bridges are one of the critical civil infrastructure for safety of traveling public. The conditions of bridges deteriorate with time as a result of material aging, excessive loading, and inadequate maintenance, etc. In this paper, the development of an autonomous robotic system is presented for highly-efficient bridge deck inspection and evaluation. An autonomous mobile robot is used as a platform to carry various non-destructive evaluation (NDE) sensing systems for simultaneous and fast data collection. Besides the NDE sensors, the robot is also equipped with various onboard navigation sensors. A sensing integration scheme is presented for high-accuracy robot localization and navigation. The effectiveness of the autonomous robotic NDE system is demonstrated through extensive experiments and field deployments.

Automated GPR Rebar Analysis for Robotic Bridge Deck Evaluation

Ground penetrating radar (GPR) is used to evaluate deterioration of reinforced concrete bridge decks based on measuring signal attenuation from embedded rebar. The existing methods for obtaining deterioration maps from GPR data often require manual interaction and offsite processing. In this paper, a novel algorithm is presented for automated rebar detection and analysis. We test the process with comprehensive measurements obtained using a novel state-of-the-art robotic bridge inspection system equipped with GPR sensors. The algorithm achieves robust performance by integrating machine learning classification using image-based gradient features and robust curve fitting of the rebar hyperbolic signature. The approach avoids edge detection, thresholding, and template matching that require manual tuning and are known to perform poorly in the presence of noise and outliers. The detected hyperbolic signatures of rebars within the bridge deck are used to generate deterioration maps of the bridge deck. The results of the rebar region detector are compared quantitatively with several methods of image-based classification and a significant performance advantage is demonstrated. High rates of accuracy are reported on real data that includes thousands of individual hyperbolic rebar signatures from three real bridge decks.

Validation of Benefits of Automated Depth Correction Method Improving Accuracy of Ground-Penetrating Radar Deck Deterioration Maps

Current ASTM specifications provide an approach for directly correlating the top rebar reflection amplitude from ground-penetrating radar (GPR) to deck condition when corrosion is the primary mechanism for concrete deterioration. However, current specifications do not offer an approach to compensate for geometric spreading losses caused by the inevitable variability in as-built concrete rebar cover. Even when cover thickness meets specified tolerances, significant errors may occur in mapping the location and quantity of deteriorated concrete when these amplitude variations are unaccounted for in air-coupled or ground-coupled GPR investigations. The significance of this correction is demonstrated by comparing mapped deterioration quantities that have been corrected and not corrected for depth variation, versus those quantities from independent methods such as half-cell corrosion potential, chain drag, or impact echo. One manual and two automated processes for depth correction are presented. These three processes compare favorably with one another on several mapped decks. One of the automated methods, which sets a deterioration threshold calibrated with half-cell and chain drag results, has been shown to be as accurate as manual methods on numerous decks. This approach is recommended for further evaluation and incorporation within ASTM D6087-08: Standard Method for Evaluating Asphalt-Covered Bridge Decks Using Ground-Penetrating Radar.

Complementary Impact Echo and Ground Penetrating Radar Evaluation of Bridge Decks on I-84 Interchange in Connecticut

Corrosion induced bridge deck delamination is a common problem in reinforced concrete decks. Complementary approach using impact echo (IE) and ground penetrating radar (GPR) testing was conducted on asphalt-overlaid bridge decks on I-84 Interchange in Connecticut. In the first phase of testing GPR survey was conducted on nine decks. The decks were GPR surveyed, at 50 km/h, with two objectives. The first one was to estimate concrete deterioration quantities (% of deck area) prior to recommending deck repair or replacement. The second objective was to identify zones of higher deterioration that were later evaluated by IE for possible delamination. A portable seismic pavement analyzer (PSPA) was used for the IE assessment on four bridge deck sections. The results of IE evaluation are presented in terms of condition assessment maps, where zones of different condition grades or different degrees of delamination are identified. The results were correlated to the GPR data to assist in definition of a suitable deterioration threshold separating sound concrete from deteriorated sections within the deck. These two non-destructive evaluation techniques, along with 15 cores and 15 chloride samples from the three decks, were used to finalize the deterioration assessment. For two of the three interstate decks tested, the PSPA testing and analysis was useful in helping establish the GPR deterioration threshold. On the third no obvious correlation could be seen, so the chloride test results were used to help constrain the GPR data.