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Ultrasonic testing (UT) is typically conducted to locate and classify (or rate) defects in welds during bridge fabrication. Variations in acoustic properties such as attenuation and velocity can ha...

As per New York State’s Uniform Code of Bridge Inspection, all bridges in New York State are inspected biennially, or more often as necessary. 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. The reliability of bridge inspection ratings depends on the quality of inspection data taken during the inspections, such as photographs, notes, etc. To evaluate the consistency of the bridge inspection quality, sufficient inspection data have been obtained from four selected bridges by 21 inspection teams. A qualitative evaluation of all inspection reports has been carried out to analyze the consistency of report items, such as notes, paragraphs, and detection of damages. The results of this analysis indicate that the current quality control procedures being used to review reports for submission allow variation in the content of the reports, where inconsistencies and omissions of some reporting items still exist. However, the overall quality of report items, such as notes, photographs, etc., was found to be very high for the New York State’s bridge inspection program.

Nondestructive evaluation (NDE) technologies are increasingly being used for the condition assessment of existing structures. In order to ensure best funding allocations and most effective maintenance and repair activities, the reliability of NDE technologies for a particular application needs to be carefully assessed to determine the margin of error (MOE) of NDE data. This research aims to investigate the utilization of “Wilcoxon-Mann-Whitney (WMW) Statistics” for the reliability assessment of NDE technologies. The reliability of three of the most widely used NDE technologies for the detection of subsurface cracking in concrete was assessed using WMW analysis. The NDE technologies assessed were: Impact Echo (IE), Infrared Thermography (IRT), and Ground Penetrating Radar (GPR). Two in-service bridge decks and two full-scale fabricated deck slabs were nondestructively tested to provide suitable data for analysis. The in-service bridge decks contained areas of mild and severe subsurface cracking as determined from previous testing performed by the Missouri Department of Transportation (MoDOT). The fabricated decks, on the other hand, contained areas of synthetic cracking of different sizes and depths. The reliability indices determined from WMW analysis for the three NDE technologies discussed in this manuscript are exactly equivalent to the indices determined previously by the same authors using Receiver Operating Characteristics (ROC) analysis. Results of WMW analysis, by the way, indicated that IE and IRT technologies were more reliable than GPR for the detection of concrete subsurface cracking. The final WMW indices of IE and IRT data were much higher than the corresponding indices of GPR data for both the in-service bridge decks and the fabricated slabs. The interesting equivalence between WMW and ROC analyses may encourage other researchers to utilize the former method in order to investigate the reliability of other NDE technologies in other applications. The findings of this research may also assist decision-makers considering the use of these NDE technologies in order to form decisions regarding maintenance and repair needs for bridges.

In this study, the performance data from 30 inspectors evaluating 147 specimens with fatigue cracks in representative in-situ conditions were analysed to identify the role of human factors in bridg...

Previous studies by the Federal Highway Administration (FHWA) have shown significant variability in the rating of bridge elements through visual inspection. In this study, a detailed evalua...

Bridge inspection results provide input for several important functions such as maintenance, repair, and rehabilitation, bridge load capacity ratings, truck load routing/permitting, and future safety/condition predictions. As a result, the quality and reliability of inspection data are important for bridge management and to ensure the safety and serviceability of bridges. Element-level data collection has been required nationwide for bridges on the National Highway System since 2014, and therefore is relatively new to some bridge owners. The objective of the research reported here was to assess the quality of element-level bridge inspection data by comparing bridge inspection results between different bridge inspectors assessing the same bridges. This paper reports results from two research studies completed to collect data on the quality (i.e., variability) of element-level inspection data. Results of field trials indicated that there was significant variability in the data for bridge elements reported in the study. Based on these data, the element-level inspection results were widely dispersed—the smallest coefficient of variation calculated from the current studies was 18%, but typical values were found to be greater than 50% in most cases, and often greater than 100%. These data provide examples from a series of field trials that illustrate the need for improving the quality of element-level inspections to ensure the reliability of the data provided.

This research investigates the potential for ultrasonic stress measurement (USM) to be used to evaluate the total stress in wide-flange steel sections (W-section) for a postevent condition ...

This paper examines the development of a Time of Flight Diffraction (TOFD) ultrasonic method for defect detection and sizing in eyebars. Eyebars from the Pasko - Kennewick bridge are utilized as test specimens to determine eyebar fatigue performance, and to test the effectiveness of the TOFD method. The test setup for making crack depth measurements in eyebars is described. Measured results of the depth of machines slot test specimens and results of fatigue crack growth are presented.

Since the collapse of the Mianus River Bridge in Connecticut in June 1983, defects in pin-hanger connections have been detected in many bridges in the United States. Pin-hanger connections are used in suspended span configurations in girder bridges and truss systems. The objective of this study is to develop a better understanding of the pin-hanger connection. Using the software package ANSYS 5.0A, a finite element model of a typical connection is generated to examine possible failure modes under several loading conditions.

Selection of the appropriate condition assessment tool to meet the decision-making needs for preservation, maintenance, and repair (PM&R) actions can be difficult, because different nondestructive evaluation (NDE) technologies have different performance characteristics. The objective of the research was to compare the reliability of ground-penetrating radar (GPR) and infrared thermography (IRT) for the detection of delamination in concrete bridge decks. Field tests were conducted on two in-service concrete decks constructed in the same era and having significant deterioration due to corrosion damage. Reliability of the technologies was evaluated using receiver operator characteristics (ROC) analysis, a methodology that allows for a quantitative point-by-point comparison of results from NDE technologies with ground truth. The analysis results quantified the reliability of IRT and GPR for the two candidate concrete decks. It was found that IRT exhibited a higher reliability measure as compared with GPR for these two bridge decks. The implication of the test results for implementation of these technologies is discussed. The results of the analysis provide useful data for bridge owners making decisions regarding suitable NDE technologies for the condition assessment of bridge decks.

This work presents an improved method for characterizing the reliability of Infrared Thermography (IRT) and determining the optimum thermal contrast for the detection of delamination in concrete. Receiver operating characteristics (ROC) analysis in conjunction with image processing methods were used to analyze data from a fabricated and in-service bridge decks. Results of the study demonstrated the excellent capability of IRT to discriminate delaminated from sound concrete. This conclusion was reached because the nonparametric estimate of the area under the ROC curve (AUC) was larger than 80% with its 95% confidence for each group of images. The optimum thermal contrast range was determined to be 0.6 ∽ 0.8 °C. Accurately defining the actual condition of the test object is critical to implement the proposed analysis method.

Visual inspection is the primary means of ensuring the safety and functionality of in-service bridges in the United States and owners spend considerable resources on such inspections. While...

Ground Penetrating Radar (GPR) is a nondestructive evaluation technique that is recently employed in various civil engineering applications such as concrete quality evaluations, locating reinforcing rebar, and bridge deck integrity assessments. Previous research has shown that the chloride and moisture content of concrete, corrosion state, and depth of reflecting objects (e.g., steel reinforcing bars) have some impact on the strength of GPR signals. What is not yet clear, however, is to what extent these factors can affect GPR response. This research has sought to quantitatively determine the effects of these factors on the attenuation and the resulting response of GPR signals reflected from reinforcing bars in concrete. The effects of these factors were experimentally demonstrated by analyzing data from four reinforced concrete slabs. Analysis of the processed data showed that attenuation was highly attributed to the depth of the reinforcing bars as compared to the concrete chloride and moisture content, where the amplitude of the reflected signals decreased by 4.5dB for every 25 mm increase in depth as compared to about 1.0 dB reduction in signal amplitude due to the presence of chloride and moisture. Corrosion of reinforcement bars, on the other hand, slightly increased the amplitude of the reflected signals by 1.0 dB.

This viewgraph presentation includes the following main concepts. Goal: To evaluate Raman spectroscopy as a potential NDE tool for the detection of stress rupture in Kevlar. Objective: Test a series of strand samples that have been aged under various conditions and evaluate differences and trends in the Raman response. Hypothesis: Reduction in strength associated with stress rupture may manifest from changes in the polymer at a molecular level. If so, than these changes may effect the vibrational characteristics of the material, and consequently the Raman spectra produced from the material. Problem Statement: Kevlar composite over-wrapped pressure vessels (COPVs) on the space shuttles are greater than 25 years old. Stress rupture phenomena is not well understood for COPVs. Other COPVs are planned for hydrogen-fueled vehicles using Carbon composite material. Raman spectroscopy is being explored as an non-destructive evaluation (NDE) technique to predict the onset of stress rupture in Kevlar composite materials. Test aged Kevlar strands to discover trends in the Raman response. Strength reduction in Kevlar polymer will manifest itself on the Raman spectra. Conclusions: Raman spectroscopy has shown relative changes in the intensity and FWHM of the ~1613 cm(exp -1) peak. Reduction in relative intensity for creep, fleet leader, and SIM specimens compared to the virgin strands. Increase in FWHM has been observed for the creep and fleet leader specimens compared to the virgin strands. Changes in the Raman spectra may result from redistributing loads within the material due to the disruption of hydrogen bonding between crystallites or defects in the crystallites from aging the Kevlar strands. Peak shifting has not been observed to date. Analysis is ongoing. Stress measurements may provide a tool in the short term.

Thermographic imaging technique provides a practical tool for the detection of subsurface delaminations in concrete from a distance without direct access to the surface. In the previous study, a numerical model to predict the thermal contrasts resulting from subsurface voids (i.e., delaminations) in concrete under a given set of environmental conditions was developed using the finite element method. The model was verified using the experimental test data, and the results indicated that the model could be an effective tool to support the thermography inspection of the concrete. In this present study, the use of the verified model to evaluate the effects of other key parameters expected to influence the detectability of the subsurface voids, such as the depth and thickness of a subsurface delamination. The effect of these parameters on the thermal contrast developed on the surface above a subsurface delamination was assessed under a specific set of environmental conditions. The results shown that the maximum thermal contrast decreased exponential by a constant multiple of 0.98 as the void depth increased and the maximum thermal contrast increased nonlinearly with increasing thickness of the void.

A significant form of deterioration in concrete is corrosion of embedded reinforcing steel that can cause subsurface delaminations and spalling. Infrared thermography can be used to detect delaminations based on variations in surface temperature that are caused by the disruption of the heat flow through the delaminated area. The surrounding environmental conditions such as sunlight, ambient temperature variation, and wind speed are critical for heat transfer, and as such the technology depends on these environmental conditions. This paper describes a numerical model developed to predict thermal contrasts for subsurface delaminations based on a given set of environmental conditions surrounding the concrete. The finite element method (FEM) was used to perform 3-D nonlinear transient heat-transfer analysis of a large concrete block with embedded Styrofoam targets intended to provide an idealized model of subsurface delaminations. The effectiveness of the modeling was evaluated by comparing the thermal contra...

The current research develops a framework to automatically extract sub-surface defects from time-lapse thermography (TLT) images of reinforced concrete bridge components. Traditional approaches for processing TLT data typically require manual interventions that are not easily scaled to a large network of concrete bridges. A backbone of robust algorithms for detecting and analyzing deep sub-surface defects in concrete is needed to support condition assessment of concrete structures such as bridges. The current paper leverages advances in adaptive signal and image processing to develop a fully automated TLT data processing pipeline that is capable of efficiently detecting defects at different depths in concrete. The methodology decomposes raw TLT datasets into narrow band time-frequency domains via a multiscale data analysis approach called a wavelet transform. The resulting decomposed modes are mined to extract defect information using thermal contrast enhancement routines. An objective measure of effectiveness based on signal-to-noise ratio was developed and used to compare the current framework with traditional approaches for processing TLT data. Active contour models were also designed to automatically extract the boundary location and geometric properties of the sub-surface defects. The results of this study show that the detection of deeper defects (3 in. and beyond) can be improved by analyzing the time-frequency response of surface temperature variations over a period of time. Compared to traditional lock-in algorithms and conventional infrared thermography images, the proposed framework is more effective at removing noisy information and produces images with greater contrast between intact and defective areas of concrete.

This paper describes the results of performance testing conducted to improve the quality of nondestructive testing (NDT) used to evaluate the structural integrity of welded-steel bridge components. Common NDT technologies, such as magnetic particle testing (MT) and ultrasonic testing (UT), rely on trained inspectors to implement the proper procedures and interpret the responses to identify and assess indications. High variability in test results can occur between qualified inspectors, who may implement the same procedures with differing levels of thoroughness and care and may interpret responses differently. As a result, the reliability of the implementation of the technology cannot be assumed. Performance testing assesses inspectors, who demonstrate their capability to implement procedures through their detection and analysis of known defects. Such performance testing can improve the quality of NDT inspections by ensuring that inspector capability is adequate. This paper describes the results of performa...

Infrared thermography has the potential to detect subsurface delaminations before spalling develops and could be used to improve the visual inspection of concrete bridges. The technology has traditionally been applied to bridge decks, which are exposed to radiant heating from the sun that helps develop the necessary thermal gradients in the concrete. Thermal gradients can also be developed from normal diurnal temperature variations. Convective heat transfer develops the thermal gradients, although these thermal gradients are of much lower magnitude than those developed through radiant heating from the sun. This paper presents the results of a study to develop thermal imaging for the detection of subsurface deterioration in the soffit areas of bridges; these soffit areas are shaded and therefore are not exposed to radiant heating from the sun. Experimental studies and field testing were conducted and are described. This paper reports on guidelines developed for this application of the technology; the guidelines address the necessary environmental conditions to enable the detection of damage in bridge soffit areas. Specifically, the paper discusses the rates of change in ambient temperature needed to ensure that subsurface damage can be detected in shaded conditions. The paper also discusses the effect of wind speed on the detectability of subsurface damage in the shaded areas of a bridge, as well as the camera settings needed to ensure that an inspector can detect temperature anomalies associated with subsurface damage. A field example is provided to illustrate the application of the technology and highlight the required camera settings.

This paper presents two case studies that were conducted to evaluate the effectiveness of a new, risk-based inspection (RBI) method. The overall objectives of the case studies were to demonstrate the implementation of the methodology and to verify the effectiveness of RBI analysis for determining suitable inspection intervals for highway bridges. Expert elicitations were conducted to develop risk-based data models for RBI analysis for two families of bridges. These data models were used to assign inspection intervals for bridges ranging from 12 to 72 months. A new backcasting method was developed and used to analyze the effectiveness of these data models for identifying suitable inspection intervals. The results of the backcasting procedures verified that the RBI approach determined suitable inspection intervals for the sample bridges assessed through the research.

This paper presents a new methodology for determining bridge inspection intervals and procedures. The methodology was developed using established risk-based methodologies with the goals of improving bridge safety and serviceability and optimizing the use of resources for bridge inspection. Current inspection intervals are calendar based and generally require routine inspections at a maximum interval of 24 months. This uniform, calendar-based approach results in the same inspection interval for new bridges and aging and deteriorated bridges. The uniform inspection interval does not consider the inspection needs for a given bridge based on age, condition, materials, environment, etc., and as a result, inspection resources may not be utilized most effectively. Using the methodology described in this paper, a bridge owner performs a simple risk-based assessment of bridges in his or her inventory to identify those for which shorter inspection intervals are needed and those for which longer intervals are more appropriate. This assessment identifies likely damage modes and associated consequences in terms of safety and serviceability of a bridge. A simple risk matrix is used to identify the appropriate inspection interval for bridges. The new, risk-based approach represents a new paradigm for bridge inspection that could transform traditional, uniform, and calendar-based inspection approaches and improve the allocation of resources for bridge inspection to improve the reliability and safety of bridges.

Thermal imaging can be used to image subsurface damage resulting from the corrosion of embedded reinforcing steel, which typically manifests as delaminations at or near the level of the reinforcing steel. Delaminations interrupt the heat transfer through the concrete, resulting in surface temperature variations that can be assessed using thermal cameras. This type of damage occurs in bridge decks, soffits, parapets, abutments and other concrete bridge components. This paper will discuss advances in the application of thermal imaging for the condition assessment of concrete bridge components, focusing on applications to the areas of the bridge not exposed to the radiant heating of the sun. Research results describing ambient temperature variations and inspection timing requirements for conducting thermal inspections are presented. Research exploring the effects of environmental parameters on the ability to image subsurface defects (delaminations) at different depths in concrete is also discussed.

After the discovery of a significant crack in an eyebar (fracture-critical element) on the San Francisco–Oakland Bay Bridge in California, the California Department of Transportation (Caltrans) explored possible remote monitor solutions to provide the greatest possible safeguards for the some 200,000 vehicles that used the bridge daily. Caltrans selected an acoustic emission (AE) monitoring system that allowed the detection and localization of crack initiation and growth in real time. The AE method relies on the propagation of elastic waves released by a sudden stress–strain change at the crack tip. The challenge of the AE method in a field application is the disturbance of the data by extraneous noise sources. A robust damage detection algorithm is required to differentiate relevant damage data from secondary noise sources, such as friction. Caltrans required that the proposed monitoring solution be validated through laboratory testing. This paper presents the full-scale laboratory testing of two eyebars loaded under constant amplitude fatigue to detect and locate crack growth under intense friction-type noise sources with use of the AE method. Verification is presented of AE results with ultrasonics testing, dye penetrant, and visual methods to detect damage. Linear location accuracy with simulated signal sources is discussed. The pattern recognition algorithm to differentiate noise signals and crack growth signals is presented. On the basis of this study, the AE method will be used to continuously monitor 384 eyebars with 640 AE sensors on the San Francisco–Oakland Bay Bridge.

This paper addresses the effect of solar loading on thermal imaging for the detection of subsurface deterioration in concrete bridge components. The deterioration of the concrete resulting from corrosion of embedded mild reinforcing and prestressing steel results in delamination and spalling that can affect the strength and serviceability of a concrete structure. The ability to detect this deterioration during its early stages, when mitigation efforts can be employed, can provide a useful tool for maintenance and inspection personnel. Infrared thermography is a tool that has the potential to detect these subsurface defects to compliment inspection efforts and provide an additional means of condition assessment for a bridge. However, the technique relies on thermal gradients developing in the concrete such that a temperature contrast exists between damaged concrete and sound concrete. The environmental conditions at the bridge, such as direct solar loading, ambient temperature variation, and wind affect the thermal gradient in the concrete, and hence, the ability to image subsurface features. The effects of direct solar loading on the detection of subsurface targets in a concrete test block have been studied. Quantitative measurements of the thermal contrast that appear in thermal images of the test block are reported and analyzed. The effect of the depth of the embedded target is discussed, as well as the timing of inspection (relative to sunrise) that resulted in maximum contrast in thermal images.

The deterioration of concrete bridge components due to corrosion presents a significant challenge for bridge owners worldwide. Deterioration commonly develops at the level of embedded reinforcing steel because of the expansion of corrosion products and resulting stresses in the concrete. As a result, deterioration cannot be detected with visual inspection until it has progressed sufficiently to be manifest in spalling or advanced deterioration of the concrete. This paper presents the results of a study to develop thermal imaging (infrared imaging) for detection of subsurface deterioration. This nondestructive evaluation technique detects delamination on the basis of resulting perturbations in the heat transfer characteristics of the concrete, which are manifest as variations in surface temperature. The technique has the advantage of being applied from a distance and thus reduces access and traffic control requirements. However, it depends on certain environmental conditions to achieve thermal gradients in the concrete needed to detect subsurface deterioration. This study explored the effects of environmental parameters on the detectability of delamination in concrete. Specifically, the effects of diurnal temperature changes on the detection of damage in the soffit area of bridges are reported. Experimental studies and field testing were conducted. This paper focuses on guideline requirements developed through the research for the effective application of the technology in the field and describes experience with application of the technology for the detection of deterioration in a typical highway bridge.

Deterioration of concrete due to corrosion of embedded steel reinforcing bars and prestressing strands represents a significant challenge for inspection and maintenance engineers. Delaminations develop in the concrete manifest as spalling, which further exposes the steel to the corrosive environment and accelerates the deterioration process. The typical method for detecting these delaminations is hammer sounding, which requires hands-on access to the material under inspection. Specialized equipment and lane closures are frequently necessary to achieve the required access. Application of infrared imaging to detect the subsurface features in concrete can image such defects from a distance, such that direct access to the surface of the concrete is not required. However, the method relies on environmental conditions to create thermal gradients in the concrete so that these subsurface features can be detected. A study examined the optimum environmental conditions for detection of subsurface features in concrete. The goal was to provide guidance on the practical application of infrared imaging for inspection of concrete bridge components. The effects of solar loading from direct sunlight and wind speed have been examined to determine their impact on the detectability of subsurface features in concrete. The optimum time of day for detection of subsurface defects and the effect of their depth is discussed. Characteristics of optimum inspection conditions for using infrared cameras in the field are described.

This article presents the results of an investigation of the Raman scattering effects of aging Kevlar strands. The goal of this research was to investigate the potential application of Raman spectroscopy as a nondestructive evaluation tool for the detection of aging effects of in-service composite materials. Kevlar composites used as overwrapping of metal-lined composite overwrapped pressure vessels (COPVs) have been analyzed. Raman spectra produced from the Kevlar fibers and the effects of resin materials, utilized to bind the fibers into strands to provide composite behavior, have been investigated. A series of Kevlar/epoxy strands exposed to elevated temperatures and sustained loading have been evaluated. It was found that this exposure had an effect on the width and intensity of certain bands in the Raman spectra of Kevlar. The potential application of these findings to the nondestructive evaluation of Kevlar composites is discussed.

This paper describes a statistical approach to estimating an appropriate inspection interval for highway bridges based on historical condition data collected from 20 years of routine inspections. Condition ratings of 4,270 bridges with concrete, steel, and prestressed-concrete superstructures were analyzed in this study to determine the time-in-condition rating (TICR) for superstructure components. The Anderson-Darling test was used to assess five conventional distributions to determine goodness of fit for describing the distribution of the TICR probabilistically. The test results revealed that the Weibull distribution was the best fit for the TICR for superstructure components. Parameters of the Weibull distribution were estimated for concrete, steel, and prestressed concrete in different condition ratings and used to define probability-density functions (PDFs), which were then used to determine the likelihood of a bridge deteriorating from a good condition to a poor condition over some time period. These data can be used for rational decision making regarding the appropriate inspection interval for bridges of a given type based on quantitative historical analysis of data. This study is beneficial because of the simplicity of the models developed and their accessibility for practicing engineers.

This paper describes a Federal Highway Administration Nondestructive Evaluation Validation Center (NDEVC) project to develop tools to better measure large-scale structures. The specific instrument discussed is a laser-based instrument that has been successfully used in a number of applications related to highway bridges. To help understand the way the instrument is used, a description of the basic system operation is given, followed by a detailed explanation of the main instrument features. Several projects conducted with this laser system are then presented as examples of the capabilities of the instrumentation. Although the system does have limitations, especially in terms of measurement range and cost, the system has proven to be versatile for a wide range of applications. Both laboratory and field applications are given. Most of the laboratory tests with the instrument have occurred at the NDEVC, which is located at the Turner-Fairbank Highway Research Center in McLean. Virginia. Field tests have taken place at several locations around the United States.

This paper describes the developments and application of a laser-based instrument used to experimentally load test bridges. The instrument is used to quickly and unobtrusively measure bridge girder deflections under static loading. The system can be set up in the median or shoulder of the roadway under the bridge without altering traffic. Data can be collected on multiple girders from one measurement location without requiring access to the girders, and no special targets are required on the girders. As a result, this type of a system can greatly speedup the process of load testing a bridge. In fact, the system can allow bridges to be load tested that would be difficult or impossible under other circumstances. To help understand the way the instrument is used, a description of the basic system operation is given followed by a detailed explanation of the main instrument features. Details of the procedure used to measure vertical deflection of bridge girders are discussed. Finally, an overview of the experimental local tests performed with the NDEVC laser system is presented.

Routine inspection is the most common form of highway bridge inspection to satisfy the requirements of the National Bridge Inspection Standards. The accuracy and reliability of documentation generated during these inspections are critical to the allocation of Department of Transportation construction, maintenance, and rehabilitation resources. Routine inspections are typically completed using only the visual inspection technique and rely heavily on subjective assessments made by bridge inspectors. In light of this, and given the fact that visual inspection may have other limitations that influence its reliability, the Federal Highway Administration initiated an investigation to examine the reliability of visual inspection as it is currently applied to bridges in the United States. This paper will summarize results from this study related to the accuracy and reliability of routine inspection documentation. A number of important conclusions were developed from the experimental study. Generally, it was found...

Concrete is a critical material for the construction of infrastructure facilities throughout the world. Traditional concretes consist of cement paste and aggregates ranging in size from 6 to 25 mm that form a heterogeneous material with substantial compressive strength and a very low tensile strength. Steel reinforcement is used to provide tensile strength for reinforced concrete structures and as a composite the material is useful for structural applications. A new material known as reactive powder concrete (RPC) is becoming available. It differs significantly from traditional concrete; RPC has no large aggregates, and contains small steel fibers that provide additional strength and, in some cases, can replace traditional steel reinforcement. Due to its high density and lack of aggregates, ultrasonic inspections at frequencies 10 to 20 times that of traditional concrete inspections are possible. This paper reports on the initial findings of research conducted to determine the applicability of ultrasonic testing techniques for the condition assessment of RPC. Pulse velocities for shear and longitudinal waves and ultrasonic measurement of the modulus of elasticity for RPC are reported. Ultrasonic crack detection for RPC also is investigated.

Concrete bridge deck deterioration is a significant problem that must be addressed to preserve highway infrastructure investments in bridges around the world. Reducing the cost of bridge deck maintenance is critical to government and private agencies responsible for maintenance of bridges. Maintenance challenges increase as many bridges begin to approach the end of their design life and traffic loads continue to increase. One means of reducing the cost of bridge deck maintenance is to accurately evaluate the condition of the structure and its constituent materials. Current methods used to evaluate deterioration of bridge decks include acoustic, electrochemical, electromagnetic, and visual inspection techniques. The purpose of this study was to assess the advantages and limitations of three available evaluation methods. The evaluation techniques included in this study were ground penetrating radar, the chain drag method, and IE. These techniques represent an important group of inspection methods currently used to evaluate in-service bridge decks. The bridge deck used in the study contains significant delaminations but exhibits virtually no outwardly visible signs of these deficiencies, so a detailed visual inspection survey of the deck was not included. Cores were taken from the bridge deck at selected locations to confirm the accuracy of the results obtained through each evaluation method. This paper presents the findings from each method and describes their respective advantages and limitations.

Reliable health monitoring, including nondestructive evaluation, is an essential part of the feedback and monitoring system for infrastructures. The goal of this paper is to provide a summary of recent research activities that will act as a catalyst to expand interest in the development of new health monitoring technologies. The paper describes the motivation for developing innovative tools for monitoring the health of the USA's infrastructure. An overview of initiatives sponsored by the National Science Foundation to develop new technologies is presented. The paper includes a review of the state-of-the-art stress-wave methods for the evaluation of structural materials and pavements at the National Institute of Standards and Technology. Finally, efforts at the Federal Highway Administration to develop new technologies for the assessment of the nearly 500 000 bridges along the USA's roads and highways are described.

There is currently widespread use of high-strength steel tendons for prestressing and post-tensioning of concrete structures and as suspension cables for long-span bridges. Tendons normally consist of one or more seven-wire, helically wound steel strands or solid rods. There are more than 130,000 prestressed bridges in the United States that contain these tendons, and approximately 3,000 new bridges are constructed each year. The prestressing tendons are critical structural elements because the forces in the tendons counteract tensile stresses in the concrete that result from loads acting on a bridge. The tendons are frequently inaccessible for visual inspections and there is currently no accepted nondestructive evaluation technique to assess the condition of these tendons. The goal of this research is to examine ultrasonic stress measurement techniques for the condition assessment of prestressing tendons. This information could be used to compare the actual force in the tendon with its design va...

The Federal Highway Administration recently conducted an investigation to assess the reliability of visual inspection of highway bridges as implemented by state departments of transportation. The study focused on routine and in-depth inspection, the two most prevalent forms of visual inspection of bridges. Because visual inspection is a highly subjective nondestructive evaluation technique, the results of these bridge inspections can be highly variable and are dependent on many factors. This study included the completion of 10 bridge inspection tasks by 49 practicing state bridge inspectors. With regard to routine inspections, this study showed that condition ratings are assigned with significant variability. Specifically, approximately 68% of condition ratings are within 1 rating point of the average. The results of the in-depth superstructure inspections indicated that these inspections are not likely to detect and identify the specific types of defects for which this inspection procedure is sometimes prescribed. Specifically, widespread defects such as those normally noted during a routine inspection are likely to be noted; however, local deficiencies, such as crack indications, are unlikely to be detected. The results of the deck delamination survey indicate that the accuracy of this type of inspection is relatively poor, with few inspection teams providing results that could be considered to accurately portray the condition of the deck.

This report presents a proposed guideline for reliability-based bridge inspection practices and provides two case studies of the application of the proposed Guideline. The guideline describes a methodology to develop a risk-based approach for determining the bridge inspection interval according to the requirements in the “Moving Ahead for Progress in the 21st Century Act (MAP-21)” legislation. The goal of the methodology is to improve the safety and reliability of bridges by focusing inspection efforts where most needed and optimizing the use of resources. The report includes two parts: Part I—Proposed Guideline for Reliability-Based Bridge Inspection Practices and Part II—Final Research Report: Developing Reliability-Based Inspection Practices that documents the entire research effort. The material in this report will be of immediate interest to bridge engineers.

This paper provides an overview of an innovative new approach for the safety inspection of highway bridges. The National Bridge Inspection Standards (NBIS) mandate a uniform 24-month inspection interval for most highway bridges. The uniform intervals were based on engineering judgment at the time the NBIS was implemented in the 1970's and do not consider the typical performance characteristics of bridges with different designs, materials, exposure environments, or existing condition. A more rational approach to determining inspection frequency and scope would consider the structure type, age, condition, environment, and other characteristics of bridges. This paper will discuss reliability-based inspection practices that utilize a risk assessment framework to determine appropriate inspection frequency and scope. This approach utilizes engineering analysis of typical damage modes and deterioration mechanisms for different types of bridges, combined with the exposure environments and loading, to assess the inspection needs for a bridge. Under such an approach, inspection efforts are focused where deterioration and damage are most likely and where consequences of that damage are greatest. The approach is intended to improve the safety of bridges by optimizing the use of resources, focusing inspection efforts where inspection needs are greatest.

In-depth inspection is one of the two most common types of bridge inspection. In contrast with routine inspection, in-depth inspection is a close-up, hands-on inspection that generally covers only a portion of a bridge. The Federal Highway Administration’s Nondestructive Evaluation Validation Center recently completed a study of the reliability of visual inspection of highway bridges. Part of this study focused on the accuracy and reliability of in-depth inspections as completed by state bridge inspectors from across the United States. Three in-depth inspection tasks were completed, two focusing on the inspection of steel superstructures and one focusing on the inspection of concrete bridge decks. Visual inspection techniques were used, with the possible use of simple inspection tools. Results show that many in-depth inspections completed by state bridge inspectors do not accurately represent the condition of the structure. In-depth inspections of the steel superstructures revealed that certain deficiencies for which this type of inspection is frequently prescribed were rarely detected. Specifically, only a small minority of state bridge inspectors located the presence of any of the existing crack indications. The delamination survey of a concrete bridge deck indicated that the accuracy of this type of inspection is relatively poor. Very few state bridge inspection teams provided results that could be considered to portray the condition of the deck accurately.

The congressionally mandated National Bridge Inspection Program requires states to inspect periodically all highway bridges on public roads, among other activities; visual inspection (VI) is the primary tool used to perform these inspections. A survey was conducted to help determine current policies and practices that may affect the accuracy and reliability of VI. The survey had three main objectives: to compile a “state of the practice” for bridge inspection, particularly as it pertains to VI; to gather information about bridge inspection management to study how inspection management may influence the reliability of inspections; and to gather data about the current use of nondestructive evaluation technologies and to identify current and future research needs. State departments of transportation, local departments of transportation, and select bridge inspection contractors participated in the survey. Conclusions drawn from this study indicate that the use of nondestructive evaluation has increased since 1993 and that the use of American Society of Nondestructive Testing Level III–certified personnel is increasing. VI was cited as the most frequently used nondestructive evaluation technique; however, vision testing for inspectors is almost nonexistent. Typically, professional engineers were not on site for inspections. State departments of transportation indicated a large demand for future research into the nondestructive evaluation of prestressed concrete superstructures and concrete decks.

Routine inspection is the most common type of highway bridge inspection completed to satisfy the requirements of the National Bridge Inspection Standards. Routine inspections of highway bridges are typically completed using only visual inspection (VI) and rely heavily on subjective assessments made by bridge inspectors. Given this practice and the fact that VI may have limitations that affect its reliability, the Federal Highway Administration completed a comprehensive study to examine the reliability of VI as it is currently practiced in the United States. The accuracy and reliability of condition ratings generated through routine inspections of six in-service and decommissioned highway bridges were studied. These timed inspections were completed in normal summer weather conditions under direct observation. To ensure that results from this study would be applicable to normal bridge inspections, state department of transportation bridge inspectors made up the study sample, which included 49 inspectors from 25 states, representing a diverse cross section of the bridge inspector population. Results of the study indicate that routine inspections are completed with significant variability. Specifically, 95 percent of primary bridge element condition ratings will vary within two rating points of the average, and only 68 percent of these ratings will vary within one rating point. Additionally, the National Bridge Inspection Standards definitions of condition rating may not be sufficiently refined to allow for reliable routine inspection results.

In this study, the ultrasonic time of flight diffraction (TOFD) method to locate and size flaws in steel members was evaluated. This was done by measuring the location and depth of flaws implanted in steel plate specimens and of a fatigue crack in the flange of a full-scale steel plate girder. The data showed that the TOFD procedure was very accurate to locate flaws (within 5% of the actual location). The accuracy of the procedure to measure flaw depth depends, however, on the proximity of the flaw tip to the scanning surface. Flaw tips at depths ≥6 mm below the scanning surface were measured to an accuracy of 20% of the actual value. When the flaw tip was at a depth ≤3 mm below the scanning surface, flaw depth was overestimated. Additional scans on the opposite surface of the material may be used, however, to overcome this limitation and to obtain an accurate measurement of such flaws. The method offered good repeatability and can be used to accurately locate and size flaws with an appropriate scanning s...

Ultrasonic inspection is currently one of the most common and reliable methods used in the inspection of hanger pins in pin-and-hanger bridge structures. Recently, a pin-and-hanger connection on a heavily traveled truck route in the Midwest showed visual indications of being deficient. Field contact ultrasonic inspections were performed on the remaining pin connections. The field inspections indicated that a number of the pins contained cracks or significant wear grooves at the pin shear planes, or both. These pins were replaced and sent to the FHWA’s Nondestructive Evaluation Validation Center for further testing in an ultrasonic immersion tank. The results of the contact and immersion tank ultrasonic studies were nearly identical. Both methods found two pins that contained transverse cracks at the level of a shear plane, with one of these cracks encompassing a majority of the pin cross section. Clearly, for the conditions found in the study, field contact ultrasonics can accurately locate defects in hanger pins.

The collapse of the Silver Bridge in Point Pleasant, West Virginia, in 1967 initiated the formal requirements for the inspection of highway bridges in the USA. Almost 30 years later, visual inspection remains the primary method of bridge inspection. However, many new and promising techniques for the nondestructive evaluation (NDE) of highway bridges have emerged in recent years through the NDE research program of the Federal Highway Administration (FHWA). These include infrared and radar imaging systems, portable ultrasonic systems, telemetry systems, laser deflection measurement systems, and many others. This paper discusses the recent development of these instruments, and the potential impact it may have on bridge inspection and bridge management systems. The paper also discusses the need for validation of system performance, and the FHWA plans to construct a national center for NDE validation at the Turner Fairbank Highway Research Center.