What is Nondestructive Evaluation (NDE)?
Recent Accomplishments and Contributions
Forensic Investigation and Technical Assistance
NDE is a means of analyzing and assessing the condition of various structural components of inservice highway infrastructure assets—pavement, bridges, and tunnels—without impairing their future usefulness.
The mission of the Federal Highway Administration (FHWA) NDE Laboratory is to conduct state-of-the-art research, development, and implementation of nondestructive testing systems and technologies to improve the Nation’s highway infrastructure assets. Since its establishment in 1998, the NDE Laboratory has been maintained as an open resource for the FHWA, State departments of transportation (DOTs), industry, and academia. The NDE Laboratory fulfills the need for unbiased expertise to evaluate emerging NDE technologies, as well as data analysis, fusion, and interpretation.
The NDE Laboratory is a world-class facility for the development and testing of NDE technologies. FHWA has recently renovated and upgraded the NDE Laboratory with state-of-the-art NDE tools to address the growing needs of FHWA and other stakeholders.
Figure 1. Image. Artist’s rendition of the NDE Laboratory.
The primary laboratory facility is a 9.4- by 8-meter facility (figures 1 and 2) with new equipment and tools, including a KUKA robotic arm (KR 10 R1100 six) with a payload of 10 kg to handle test specimens, NDE equipment such as a phased array ultrasonic testing system for steel component inspection, and ground penetrating radar for concrete inspection.
Figure 2. Photograph. The NDE Laboratory.
- Development of Phased-Array Ultrasonic Testing Acceptability Criteria (Phase II), Publication Number: FHWA-HRT-14-075, Date: October 2014.
- Development of Phased-Array Ultrasonic Testing Acceptability Criteria (Phase I), Publication Number: FHWA-HRT-14-074, Date: October 2014.
Journal and Conference Papers
- “Ultrasonic Imaging of Multi-Layer Concrete Structures.” NDT and E International, DOI: 10.1016/j.ndteint.2018.04.012, 2018.
- “Nondestructive Testing of Steel Corrosion in Prestressed Concrete Structures Using the Magnetic Flux Leakage System.” Journal of the Transportation Research Board.
- “Reducing Thermal Reflections for Infrared Thermography Applications on Tunnel Liners with Reflective Finishes.” Dewei Meng and Hoda Azari. Transportation Research Board (TRB) 98th Annual Meeting, D.C., 2018.
- “Ultrasonic tomography for imaging multilayer concrete structures.” Transportation Research Board (TRB) 98th Annual Meeting, D.C., 2018.
- “Estimation of Wave Velocity for Ultrasonic Imaging of Concrete Structures Using the Dispersion Analysis Method.” Transportation Research Board (TRB) 98th Annual Meeting, D.C., 2018.
- “Performance of Concrete Bridge Decks of Similar Construction and Environment but different traffic loads.” Transportation and Research Record, Vol. 2550, pp. 22–30, 2016.
- “Characterization of Deterioration Progression in Concrete Bridge Decks from Periodical Multi NDE Technology Surveys.” The International Symposium Nondestructive Testing in Civil Engineering (conference paper), September 2015.
- “Concrete Bridge Deck Deterioration and Its Detection and Characterization Using a Fully Autonomous Robotic Platform.” The International Symposium Nondestructive Testing in Civil Engineering (conference paper), September 2015.
- “Evaluation of Phased-Array Ultrasonics on Butt Welds Using Proposed AWS D1.5 Annex, Advanced Ultrasonic Examination.” Transportation and Research Board, 2014.
- “Development of Phased-Array Ultrasonic Testing in Lieu of Radiography for Testing Complete Joint Penetration (CJP) welds.” Proceeding SPIE. 9063, Nondestructive Characterization for Composite. Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security, April 2014.
Arlington Memorial Bridge
In response to a request on February 2015 by the FHWA Eastern Federal Lands (EFL) office and the National Park Service (NPS), the FHWA NDE Laboratory in close coordination with the Long-Term Bridge Performance (LTBP) Program, provided technical assistance and evaluated the condition of the deck of the Arlington Memorial Bridge (AMB) using the RABIT™ bridge deck condition assessment robot and other advanced NDE technologies. The evaluation included condition evaluation and assessment of the deck with respect to:
- The concrete quality (degradation) and the corrosive environment.
- The extent and severity of delamination and overlay debonding in the deck.
FHWA EFL was briefed about the findings of the AMB testing and evaluation. Maintenance and management alternatives and recommendations were discussed in the briefing.
Yerba Buena Tunnel
In January 2016, a chunk of concrete from the tunnel liner fell into the travel way of the Yerba Buena Island Tunnel. In response to this event, the California Department of Transportation (Caltrans) immediately conducted an indepth visual inspection and sounding of the tunnel lining walls and identified additional areas of distress. This issue has raised Caltrans Management’s concern about the public's confidence in using the tunnel. Because of the sensitivity of this issue, Caltrans requested that the FHWA provide an independent evaluation of their assessment of the tunnel lining condition. To support FHWA’s work, Caltrans provided traffic control and the equipment needed to access the tunnel lining (e.g. bucket lifts to access the top 5 feet of the tunnel walls).
To assist Caltrans to validate their sounding results, the FHWA team conducted comprehensive non-destructive testing using different NDE techniques on the eastbound side of the Yerba Buena Tunnel, including:
- LiDAR (Light Detection and Ranging)
- Infrared Thermography (IR)
- Impact Echo (IE)
- Ground Penetrating Radar (GPR)
- Electrical resistivity (ER)
The FHWA NDE Laboratory initiated the development of the NDE Web Manual, a Web tool for assisting bridge practitioners with the proper selection of NDE technologies for the condition assessment of bridge decks and superstructures. This manual, a product of an FHWA Strategic Initiative project, presents a comprehensive selection and descriptionof NDE technologies to fill a gap between the practitioners dealing with bridge performance challenges on a day-to-day basis and the researchers developing and refining NDE technologies. This version of the NDE Web Manual presents current, unbiased, and reliable information about NDE technologies for concrete and steel bridge members, including the application, description, physical principle, data acquisition, data processing, data interpretation, advantages, and limitations of each NDE technology. Future versions of the NDE Web Manual would include information about applications of NDE tools for bridge substructures, tunnels, and pavements.
FHWA Nondestructive Evaluation and Structural Health Monitoring Workshop
In June 2016, the FHWA convened a diverse group of experts at the National Academies of Science to develop, discuss, and debate future research directions for existing and emerging assessment technologies (inclusive of both nondestructive evaluation (NDE) and structural health monitoring (SHM)).
Motivation and Objectives
From a broad perspective, the first overarching aim of the workshop was to begin to foster communication and collaboration between the end-users of NDE/SHM technologies and the researchers that are engaged in their development and refinement. The second overarching goal of this workshop was to bring NDE and SHM communities together to promote and identify opportunities for the integration of NDE and SHM.
In addition to these broad objectives, the following more detailed goals were also identified to ensure tangible products that may make near-term impacts on the field.
- Identification of guidance needs, strategies, and delivery mechanisms to effectively promote and enable the effective adoption of SHM approaches by end-users.
- Development of an NDE research roadmap for transportation infrastructure (inclusive of integration opportunities with SHM).
Summary of Key Workshop Outcomes
Foster Ongoing Government-Industry-Academe Collaboration—Throughout the workshop a strong consensus emerged that the integration of end-user and research perspectives together with collaboration between NDE and SHM researchers is essential to moving the use of assessment technologies forward. To maintain the momentum developed during the workshop, it was strongly recommended that FHWA work to develop a diverse government-industry-academe working group that meets regularly to continue to debate and discuss the issues surrounding NDE and SHM research and implementation. Although there are several NDE- and SHM-focused committees at numerous professional societies, none include the auspices of the American Association of State Highway and Transportation Officials (AASHTO) Subcommittee on Bridges and Structures. This was viewed as a significant shortcoming.
SHM Guidance—Recommendations for SHM guidance were developed through breakout sessions, discussed during open sessions, and then ranked through a poll of the workshop participants. The top three recommended forms of guidance were:
- Web Manual—Expand the current NDE Web Manual to include SHM technologies and techniques. This format not only provides open access to all end-users, but can also be updated frequently to include recent developments.
- Case Studies—The detailed documentation of complete SHM case studies was viewed as especially important to provide tangible examples to end-users. The inclusion of unsuccessful case studies (together with successful case studies) was of particular interest.
- Synthesis Report—The development of a synthesis report that documents both domestic and international practices and policies related to SHM.
NDE Research Roadmap—Recommendations for specific NDE research topics were developed through breakout sessions, discussed during open sessions, and then ranked through a poll of the workshop participants. The top six research topics were:
- Data Fusion, Analysis, Visualization—Data has become easier and cheaper to collect, but the ability to fuse disparate data sources, efficiently process data (without extensive expertise), and develop visualizations that permit intuitive interpretation remain elusive.
- Measurement of Intrinsic Stress—Although in many structures intrinsic stresses (inclusive of dead load, manufacturing/fabrication, etc.) overwhelm transient, live load stresses, there is currently no reliable and nondestructive approach to estimating them.
- Quantification of NDE Reliability—In order to employ NDE approaches to effectively inform decisions, it is imperative that the reliability of such techniques (e.g. probability of false positives and false negatives) be established.
- Establishing the Cost-Benefit of NDE/SHM—The inability to accurately estimate the return on investment (ROI) associated with NDE and SHM was viewed by the workshop participants as the most significant barrier to their implementation.
- Estimation of Remaining Service Life—The translation of NDE and SHM data into reliable estimates of remaining service life is critical to informing decisions related to repair, retrofit, and replacement.
- Monitoring Corrosion, Corrosion Rate, Section Loss—Although corrosion is responsible for a large portion of the degradation of transportation infrastructure, there are currently no direct measurement methods available to identify and track its progression.
FHWA Workshop in Advanced Ultrasonic Inspection Applications for Steel Bridge Welds
FHWA and the National Steel Bridge Alliance cohosted an NDE workshop at Turner-Fairbank Highway Research Center on May 31 and June 1 entitled “Advanced Ultrasonic Inspection Applications for Steel Bridge Welds.” Cutting-edge NDE techniques are under investigation at TFHRC as a possible alternative to radiography for the inspection of steel welds in new fabrication bridges. The techniques are also of interest for application on inservice bridges to monitor known or suspected problematic flaws. The workshop included approximately sixty representatives from State transportation agencies, FHWA, USACE, advanced ultrasonic system equipment manufacturers, academia, and contractors.
MOTIVATION AND OBJECTIVES
The workshop primarily focused on the emerging Phased Array Ultrasonic Testing (PAUT) technique and Full Matrix Capture/Total Focusing Method (FMC/TFM). The FMC/TFM technology is an industrial spinoff of advanced image processing techniques used in radar, sonar, and medical imaging applications. The concept is similar to the relatively old Synthetic Aperture Focusing Technique (SAFT) for image processing, but the multiple sensor location information required by SAFT is obtained by the multi‑element PAUT probe in lieu of multiple single sensor locations. The availability of more powerful computing capability in laptops and portable ultrasonic equipment has enabled ultrasonic equipment manufacturers to further develop and bring this image processing capability to the field for real-time high-resolution imaging.
SUMMARY OF KEY WORKSHOP OUTCOMES
The images provided by the FMC/TFM process result in improved weld-flaw sizing and characterization information. The improved flaw sizing and characterization is of interest to owners of existing bridges with weld flaws that need to be evaluated in detail for repair or monitored. The improved flaw information provides engineers with more reliable information to assess the significance of these known flaws. For new fabrication bridges, this FMC/TFM technology has the potential to be used to support the elimination of radiography from the bridge fabrication specification AWS D1.5. Radiography is a costly inspection method when compared to ultrasonics and comes with scheduling and radiation hazard concerns. At the workshop, numerous bridge fabricators commented on their interest in eliminating the radiography requirement.
With overall positive enthusiasm by the attendees to further evaluate and pursue this technology, followup actions were identified at the end of the workshop. These plans include a more detailed evaluation of the FMC/TFM technique at a bridge fabricator’s facility, possibly on the production line of new steel bridge girder fabrication welds.
FHWA has recently renovated and upgraded the NDE Laboratory to address the growing research needs of stakeholders. Current expertise at the laboratory includes: conventional/phased array ultrasonic testing; conventional/advanced eddy current testing; acoustic emission; ground penetrating radar testing; infrared thermography testing; impact echo testing; surface wave testing; SHM systems; noncontact and remote sensing; numerical simulation; automated data collection, analysis, interpretation, visualization and data fusion. In conjunction with this expertise, an extensive collection of concrete/steel specimens and commercial test equipment are available at the NDE Laboratory.
The NDE laboratory conducts state-of-the-art research, development, improvement and implementation of NDE systems and technologies to assist infrastructure owners. This work includes condition assessment of inservice tunnels, pavements, and bridges, as well as providing technical assistance and forensic investigation services in examining the nature and causes of anomalies or failures of highway infrastructure assets.
The NDE Laboratory maintains an extensive collection of commercial and emerging test equipment. Click here for a more detailed list of equipment.
- Loading Frame and Environmental Testing Chamber
- Lab-based large specimen scanning systems: XY Scanner and Robot Scanner
- Concrete Electrical Resistivity Meter
- Galvanostatic Pulse Measurement (GPM) System
- Ground Penetrating Radar (GPR) System
- Half-Cell Potential (HCP) Corrosion Analyzing Instrument and Probe
- Impulse Response (IR) Testing System
- Infrared Thermography Camera
- Ultrasonic Pulse Echo (UPE) System
- Ultrasonic Surface Waves (USW) Testing System
- Portable Automated Acoustic Array System
- Acoustic Emission Data Acquisition System
- Eddy Current Testing (ECT) Instrument and System
- Portable Phased Array Ultrasonic System
- Ultrasonic Testing (UT) Device