The The Federal Highway Administration’s (FHWA’s) Advanced Sensing Technology (FAST) Nondestructive Evaluation (NDE) Laboratory is carrying out several new research concepts within its research program. Projects are largely determined based on the FHWA NDE Program Strategic Plan.
- Magnetic-based NDE system for corrosion detection internal post-tensioned (PT) tendons and anchorage zones using Main Magnetic Flux Method (MMFM) technique:
For the external tendons, two types of magnetic main flux method (MMFM) systems—a solenoid type and a permanent magnet type—were developed and validated in the laboratory and in the field. The solenoid type MMFM system was the most accurate NDE method. The conservative damage detection limit would be 0.4 percent section loss for the point measurement method and 1.0 percent section loss for the scan measurement method. Despite a major drawback of requiring time-consuming on-site preparation, the solenoid type MMFM system is the best NDE system to be used when accurate damage assessment is needed for external PT tendons. The permanent type MMFM system is suitable for locating potential problem areas containing more than 3.0 percent section loss in external PT tendons. It has more versatile applications in the field because of its simpler hardware and speedy operation. The latest RFM prototype was able to detect section losses larger than 15.3 percent in internal tendons surrounded by vertical rebars at 6-inch or wider spacing and the concrete clear cover less than 7.4 inches for metal ducts and 6.4 inches for PE ducts. The minimum number of 0.6-inch 7-wire strands needed to detect damage reliably appeared to be 10. Without interference from the vertical rebars, as little as 9.0 percent section loss can be identified at the 6.0-inch cover.
- A magnetic-based NDE system was developed for corrosion detection in prestressed concrete structures using Magnetic Flux Leakage (MFL) techniques:
The MFL technique is the most effective NDE tool that can detect the extent of corrosion or fracture of prestressing steel in concrete. Concrete deterioration and corrosion of steel in prestressed (PS) concrete bridge I-girders are primary concerns for bridge owners and engineers. Currently, most condition assessment of such bridge members are done using visual inspection. While important, visual inspection cannot reveal PS steel corrosion particularly at the early stages. The objective of this study was to design and fabricate a magnetic-based non-destructive testing (NDT) system that can scan the length of PS concrete I-girders in highway bridges and detect corrosion in the prestressing steel embedded in concrete. This project has led to the design and fabrication of a robotic transport system (the robotic rover) that facilitates the scanning of the underside of PS concrete bridge I-girders with a newly developed magnetic flux leakage (MFL) NDT system (the payload). The NDT payload (magnets/sensors assembly) uses the magnetic flux leakage concept to detect corrosion of prestressing steel within concrete. The robotic rover and NDT payload are designed and fabricated as two modular sub-systems that operate independently. This concept allows the new NDT payload to be easily removed and replaced with another payload sub-system equipped with a different NDT device/concept to facilitate complimentary NDT assessment of PS concrete I-girders in bridges.
- Develop recipes for concrete reference specimens: the goal of this study is to establish a basis of comparison between specimens, and to develop a framework for a quantitative performance comparison of NDE methods for concrete bridges. Recipes should be established for construction of well-designed reference specimens representing at least four common problems in concrete structures. These four testing problems include corrosion (or section loss) of reinforcement or prestressed tendons embedded in concrete, vertical cracks, delamination, and honeycombs. The recipe procedures are being defined and established in a way that the reference specimen is easily reproducible in any laboratory. These specimens can be utilized for comparing service providers, comparing methods, validation, benchmarking research and development, definition of test task, specification of work, training, and certification.
- Robotic air coupled acoustic array: the goal of this study is to develop a noncontact acoustic array that can be deployed on a robotic platform system for accurate and quick imaging of flaws inside concrete bridge decks. The hardware and software parts of the device are substantially improved to reduce noise, and accurately measure the acoustic response of concrete. The device uses 40 microelectromechanical systems (MEMS) microphones to capture stress waves, which are further analyzed to evaluate the phase velocity and impact-echo response of concrete. The results from the recent application of the air-coupled acoustic array system to detect flaws in the Haymarket Bridge deck slabs are quite promising. This shows great potential for further application of the system to inspect highway infrastructure.
- Evaluation of the latest phased array ultrasonic bridge weld inspection technologies and generating the qualification data to enable ultrasonic test techniques to replace the radiography requirements in the American Welding Society (AWS) bridge welding code, D1.5. Tasks include: evaluating full matrix capture (FMC) and total focusing method (TFM) technology to improve AWS D1.5 ultrasonic flaw characterization; ultrasonic modeling to evaluate AWS D1.5 flaw detection performance, including the generation of virtual qualification data using simulation software; and the evaluation of new advanced technologies for potential incorporation in AWS D1.5, including two- dimensional phased array ultrasonic testing (PAUT) arrays and time-of-flight diffraction (TOFD) techniques.
- Pavement, tunnel, and timber bridge modules for the FHWA NDE Web Manual: The objective of this project is to extend the coverage of the NDE Web Manual to include pavements, tunnels, and timber bridges. The NDE Web Manual was conceived as a problem-focused tool to provide concise and unbiased guidance to help practitioners identify the technologies that can serve their specific needs. All the webpage materials are prepared and logic connections between NDE tools and defect are developed. This project is under the development of related webpages.
- Improved Infrastructure Assessment through the Integration of Nondestructive Evaluation (NDE) and Structural Health Monitoring (SHM) Paradigms:
Load rating is one of the most common methodologies for evaluating the load carrying performance of a bridge, whereby the capacity of individual members is compared to the dead-load and live-load demands. This work provides guidance on how to integrate both nondestructive evaluation (NDE) data and field-data from structural health monitoring (SHM) to obtain load ratings that more reliably represent a bridge’s load carrying performance.
- Assessing Dead Load Stresses for Steel Bridge Members Non-destructively with Vibration Response: Stress assessment plays a crucial role in maintenance and fatigue-life prediction of bridges. This project presents analytical and numerical procedures for estimating intrinsic stresses based on vibration responses of the structure. This vibration-based approach uses classical models and numerical analysis to provide correlations between modal vibration parameters of the structure, i.e., natural frequencies and mode shapes with stresses in the structural model. The analytical and numerical analysis of this project have been performed. Results showed the distinctive changes in modal properties of the representative beam girder while the dead load and boundary conditions change.
- Validating Density Profiling Systems (DPS) for Asphalt Compaction Assessment: As the DPS technology needs to be proven as a tool for quality assurance of asphalt compaction, the measured values of dielectric should be accurately converted to the pavement properties related value (percent air voids - Va%). Therefore, the scope of this research is to evaluate the development of DPS data collection protocols by assessing:
- Aggregate type, size (NMAS) and distribution (gradation) effects.
- Binder type effects
- Number of data collection passes needed to assess compaction quality of the full lane width
- Data collection pattern, speed and location based on different construction traffic control methods
- Evaluate equipment requirements
- Collaborative Highway Asset Research: Integrated Sensor-Model Application (CHARISMA): This project develops a non-proprietary, open-source software platform (CHARISMA) to analyze and visualize NDE and other infrastructure data with a long-term goal to fuse sensor data with digital twin / physics-based BIM models. The CHARISMA infrastructure acts as a repository of traditional and machine -learning analysis algorithms that can be shared between stakeholders and improved following open-source principles. CHARISMA can be leveraged by industry to foster the integration of asset inspection, management, and project delivery data for better asset management decision making and facilitating stakeholder collaboration and participation to advance NDT/E and BIM research.
- NDE Data Fusion and Visualization: The purpose of a data fusion and visualization study is to investigate visualization schemes and fusion of NDE data, and to develop a holistic NDE visualization scheme that (1) conveys meaningful and actionable information about the infrastructure that would trigger an intervention, and (2) is understandable by individuals without an extensive background in NDE. With this focus on visualization, it is of interest to develop NDE data fusion strategies and algorithms that enhance the ability of the data visualization scheme to convey information related to the condition, performance, and safety of bridges.