Since 2008, the following projects have been completed by the Nondestructive Evaluation (NDE) Laboratory:
The Evaluation of Section Loss Due to Corrosion in Single and Multi Plate Gusset Connections Using Non-Destructive Technologies (NDT) provided an initial examination of the capabilities of NDT systems for the inspection of steel truss gusset plates. The study focused on two ultrasonic testing systems: A phased array ultrasonic system, and a conventional single-element dry-coupled ultrasonic system. The results from tests on single plates ranging from 0.36 to 0.74 inches in thickness and with various geometries of section loss were presented and compared. A feasibility study for the inspection of hidden corrosion in multi plate gusset plate connections was also presented.
The Steel Bridge Testing Program (SBTP) focused on detecting and characterizing fatigue cracks on steel girders at high stress or critical detail locations where the presence of growing cracks is possible. In addition, locations with high concentrations of stress, particularly at steel weldments and sharp corners, were of interest. Several advanced commercially available crack detection and crack growth detection (crack monitoring) technologies were evaluated through an in-depth laboratory testing (phase I). In phase II, testing of these technologies was conducted in the field and at actual bridge sites.
The objective of the Load and Resistance Factor Rating (LRFR) Procedures for Response-Based Rapid Load Rating of Steel Bridges project was to develop procedures and tools (hardware, software, algorithms, and equations) for converting field strain measurements into load rating for bridges that have calculated load ratings requiring them to be posted. The objective was to improve existing ratings of deficient steel bridges to benefit from field measurements representing the actual bridge response to actual bridge loads, and from Load and Resistance Factor Design (LRFD)/LRFR reliability theory. This response-based approach expedites load testing and rating, and alleviates the expense and logistics of conducting a bridge load test, the need to collect detailed traffic, and the development and execution of a calibrated finite element model and analysis of the bridge.
The objective of the Load and Resistance Factor Rating (LRFR) Procedures for Response-Based Rapid Load Rating of Prestressed Concrete Bridges project was to produce an LRFR procedure and tools (hardware, software, algorithms, and/or equations) for converting field strain measurements into load rating for prestressed concrete bridges that have calculated load ratings requiring them to be posted. Additionally, the objective was to improve existing ratings of deficient prestressed concrete bridges to benefit from field measurements representing the actual bridge response to actual bridge loads, and from LRFD/LRFR reliability theory. This response- based approach will expedite load testing and rating, and alleviate the expense and logistics of conducting a bridge load test, the need to collect detailed traffic, and the development and execution of a calibrated finite element model and analysis of the bridge.
The objective of the Study of Local Vibrations in Stressed Steel Beams was to validate protocols for selection and placement of sensors and data acquisition to effectively monitor salient features of local vibratory response in a steel beam in flexure and to test the ability to analyze vibratory response signature under controlled impact loading and isolate salient modes, and finally to quantify the correlation and variability between vibratory response and flexural stress magnitude.
The past decade has seen new, emerging innovation of Ultrasonic Testing (UT). Specifically, multiple manufacturers have produced Phased Array Ultrasonic Testing (PAUT) systems. The PAUT systems embed a matrix of multiple (some up to 128) single transducers into one probe used for scanning elastic materials. Simultaneously exciting multiple transducers offers distinct advantages; depending on the sequencing of transducer excitation, the ultrasonic beam could be steered within the material and multiple beams help develop extra dimensional data to assist with visualization of possible flaws including the discontinuity size, shape, and location. The objective of the Development of Phased Array Ultrasonic Testing Acceptability Criteria project, which was performed in three phases, focused on improvement to existing protocols and methods to develop acceptability criteria for PAUT technology as defined in the American Welding Society (AWS) D1.5 “Bridge Welding Code.”
The NDE Center 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 deck and superstructure. This manual, a product of an FHWA Strategic Initiative project, presents a comprehensive list of NDE technologies to fill in a gap between the practitioners dealing with bridge performance challenges on a day-to-day basis and the researchers developing and refining NDE technologies serving them. 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.
A study was completed on the Performance Evaluation of Bridge Weigh-in-Motion (WIM) Systems. The objectives of this project are to identify and compare the accuracy of WIM systems for bridge applications. This evaluation will compare capabilities with respect to providing repeatable, research-quality measurements of axle weight and spacing, vehicle speed, and identification of vehicle classification for trucks as they pass over bridge structures.
An effective and promising solution to the time-consuming process of inspecting highway structures using conventional acoustic techniques is to eliminate the need for physical contact between the sensors and a structure through the application of contactless acoustic sensors. In the study Robotic Air-Coupled Acoustic Array for High Speed Nondestructive Evaluation of Highway Structures, researchers at the FHWA’s Advanced Sensing Technology (FAST) NDE laboratory used contactless acoustic receivers to develop a noncontact, air-coupled acoustic array to inspect bridge decks. This air-coupled system is mounted on a robotic platform for the high-speed inspection of bridge decks.