Kien Dinh

Clustering-Based Threshold Model for Condition Assessment of Concrete Bridge Decks with Ground-Penetrating Radar

Ground-penetrating radar (GPR) has been extensively studied for condition assessment of concrete bridge decks in North America. Although several methods for analyzing GPR data have been proposed, the commonly accepted method evaluates the condition of concrete bridge decks on the basis of the difference between reflection amplitudes of the top rebar layer. It is assumed in the method that strong reflection indicates sound concrete, whereas the area with high-amplitude attenuation is associated with concrete corrosion. The final result is a contour map of reflection amplitude in decibel scale with the thresholds selected arbitrarily to define the severity of concrete deterioration. Because subjective determination of threshold values may lead to inconsistency in the result obtained, this paper proposes a robust method for resolving that issue. Specifically, after depth correction was performed for top rebar amplitudes, on the basis of K-means clustering technique these amplitude data were grouped into a number of condition categories. Through two case studies in North America, the methodology was implemented and compared with the results provided by other technologies, namely, concrete resistivity, half-cell potential, and laboratory chloride content analysis. The implementation showed that while the proposed method was simple to employ, it still provided reasonable results that were in line with the outputs provided by the other techniques.

Capture and Quantification of Deterioration Progression in Concrete Bridge Decks through Periodical NDE Surveys

AbstractMonitoring the condition of concrete bridge decks is essential because bridge decks are deteriorating faster than other bridge components. This study concentrated on bridge deck condition assessment using complementary nondestructive evaluation (NDE) techniques. The assessment had three main components: evaluation of the corrosive environment and corrosion processes, concrete degradation evaluation, and assessment with respect to deck delamination. Five NDE techniques were used: impact echo (IE) to detect and characterize delamination, ground-penetrating radar (GPR) to describe the corrosive environment, measurement of the concrete cover and description of its overall condition, half-cell potential (HCP) to assess corrosion activity, ultrasonic surface waves (USW) to describe concrete quality, and electrical resistivity (ER) to estimate corrosion rate. The ability of NDE methods to objectively characterize deterioration progression is illustrated by the results from four NDE surveys of a bridge in...

RABIT: implementation, performance validation and integration with other robotic platforms for improved management of bridge decks

Accurate condition assessment and monitoring of concrete bridge deck deterioration progression requires both use of multiple nondestructive evaluation (NDE) technologies and automation in data collection and analysis. RABIT (robotics assisted bridge inspection tool) for bridge decks enables fully autonomous data collection at rates three or more times higher than it is typically done by a team of five inspectors using manual NDE technologies. The system concentrates on the detection and characterization of three most common internal deterioration and damage types: rebar corrosion, delamination, and concrete degradation. For that purpose, RABIT implements four NDE technologies: electrical resistivity (ER), ground-penetrating radar (GPR), impact echo (IE) and ultrasonic surface waves (USW) method. High productivity and higher spatial data resolution are achieved through the use of large sensor arrays or multiple probes for the four NDE methods. RABIT surveys also complement visual inspection by collecting high resolution images of the deck surface, which can be used for crack mapping and documentation of deck spalling, previous repairs, etc. The NDE technologies are used in a complementary way to enhance the overall condition assessment, certainty regarding the detected deterioration and better identification of the primary cause of deterioration. RABIT’s components, operation, field implementation and validation, as well as future integration with a robotic platform for minimally invasive rehabilitation, are described.

Attenuation-Based Methodology for Condition Assessment of Concrete Bridge Decks Using GPR

Reflection amplitude at top rebar layer has been used as a main criterion for evaluating attenuation of ground-penetrating radar (GPR) data from concrete bridge decks. However, a recent study has pointed out the limitation of this practice. Motivated by that same research, the current paper presents a robust method for performing GPR attenuation analysis. Also based on correlation between A-scans, however, instead of baseline data, semi-simulated waveforms are used in this approach. With only one reflection representing direct coupling, these waveforms mimic A-scans collected from completely damaged location. The output obtained is then plotted in form of a contour map of correlation coefficient in which higher value indicates more deteriorated concrete. As a validation, the method was implemented for two bare concrete bridge decks. The result indicates that while the maps provided by other technologies and GPR are geometrically correlated, in comparison with conventional amplitude analysis, the proposed model provides better vision on overall deterioration of

Three-Dimensional Visualization and Presentation of Bridge Deck Condition Based on Multiple NDE Data

AbstractA method is developed for presentation of a concrete bridge deck condition assessed by multiple nondestructive evaluation (NDE) technologies using a three-dimensional (3D) visualization pro...

Performance of Concrete Bridge Decks of Similar Construction and Environment, but Different Traffic Loads

Maintenance, rehabilitation, and replacement of reinforced concrete decks are the largest bridge component expenditures for most transportation agencies. Therefore, concrete bridge deck performance was identified as one of the key bridge performance issues in the Federal Highway Administration’s Long-Term Bridge Performance Program. To improve knowledge of bridge deck performance, high-quality quantitative performance data should be collected periodically through the use of complementary nondestructive evaluation (NDE) technologies, such as impact echo, ground penetrating radar, half-cell potential, ultrasonic surface waves, and electrical resistivity. This paper presents the condition change of a bridge deck in Virginia over a period of six years. The assessment covered corrosive environment and corrosion processes, concrete degradation, and deck delamination. Deterioration progression from periodic NDE surveys is illustrated qualitatively by condition maps and quantitatively by condition assessment numbers. The results demonstrate the ability of NDE technologies to capture and quantify the progression of deterioration. Strong agreement between different NDE technology results improves the confidence level of the condition assessment of the deck. The study also evaluated the similarities in performance of bridge decks of comparable age, similar construction, and similar environment, with different traffic loads. Multiple NDE technologies were used to assess two concrete decks of a similar design, construction, age, and environment, but with different traffic conditions. The complementary use of multiple NDE technologies identified corrosion as the primary cause of damage in both decks. The severity of deterioration differed at the time of the survey, which caused the estimated remaining life of the two decks to differ by about 10 percent.

Similarities and differences in bare concrete deck deterioration curves from multi NDE technology surveys

Reinforced concrete decks are in most cases the fastest deteriorating components of a bridge due to the multitude of influencing factors: direct traffic loading and environmental effects, maintenance activities (salting), etc. Among many deterioration types, corrosion-induced deterioration is the most common problem in reinforced concrete decks. The study concentrates on the condition assessment of bridge decks using complementary NDE techniques. The assessment has three main components: assessment of corrosive environment and corrosion processes, and assessment with respect to the deck delamination. The study concentrates on a complementary use of five NDE techniques: impact echo (IE) to detect and characterize delamination, ground penetrating radar (GPR) to describe the corrosive environment and detect delamination, and electrical resistivity (ER) to estimate the corrosion rate by measuring concrete resistivity. The ability of the NDE methods to objectively characterize deterioration progression is illustrated by the results from NDE surveys of 10 bridges of different ages in New Jersey during a period of one year. The deterioration progression is illustrated by condition maps and condition indices. As demonstrated in the paper, multiple deterioration models are developed utilizing the proposed methodology, which shows high potential for development of more realistic deterioration and life cycle cost models for bridge decks.

Advanced Integration and 3-D Visualization of Data from Multiple Nondestructive Evaluation Technologies

This paper presents a novel method for presenting the concrete bridge deck condition assessed by multiple nondestructive evaluation (NDE) technologies using a three-dimensional (3D) visualization program, NDEFuse. Six types of NDE data can be visualized: (1) impact-echo data for mapping and describing the depth and severity level of concrete delamination, (2) ultrasonic surface wave data for concrete quality (elastic modulus) assessment, (3) electrical resistivity for the description of corrosive environment and estimate of the corrosion rate of steel reinforcement, (4) mapping of top rebar layer and (5) ground penetrating radar condition assessment data, and (6) high-resolution deck surface image for documenting signs of deterioration, previous repairs, and surface wear. The 3D visualization platform integrates and visualizes the six NDE results in a very intuitive way. Correlations between the different types of NDE survey results were established visually in a 3D space utilizing the developed program.