FHWA NDE CENTER RESEARCH & DEVELOPMENT
Current Projects
Active Thermographic Crack Detection
Fatigue crack detection is important in structural components. The Federal Highway Administration (FHWA) Nondestructive Evaluation (NDE) Center has a number of instruments designed to detect and size fatigue cracks
in steel bridge members. Existing technologies are geared toward detection of cracks in localized areas. These conventional
techniques are typically time consuming to perform and required a trained operator. The ability to easily detect cracks over a large
area with results that are easily interpreted would be beneficial. For these reasons the FHWA research program has sponsored the
development of a active thermographic crack detection system. This system applies a flash of heat into a specimen and monitors the
flow of heat with thermal cameras. The presence of cracks can be seen in the resulting thermal response. Defects can be detected
through typical layers of bridge coatings. The instrument can cover a wide field-of-view and produces images that can be easily
interpreted.
Wingwall Displacement Measurements
A long-term monitoring system was designed and built for measuring possible movements in a wingwall of a bridge abutment in
Washington, D.C. The system uses a low-cost electromagnetic displacement sensor to measure wall movements.
Pin and Hanger Inspection Tools
Pin and hanger connections were designed into bridge structures as a means to accommodate thermal expansion of bridge girders at a
point other than the bearing. One reason for the design was to move the expansion joint of the bridge away from the bearing;
reducing corrosive materials washing down from the bridge deck. However, these corrosive material (de-icing salts) now wash down
to the pin and hanger connection. Typical problems with this connection are corrosion building up between the pin and the
hanger and the hanger and the girders. This corrosion can cause the connection to lock-up and not allow the bridge to thermally
expand and contract. The result of a locked-up connection can be fatigue cracks in the pins or hanger plates.
Although pin and hanger connections are no longer designed into new bridge structures, the number of connections in existing
bridges present problems for bridge inspectors. The FHWA NDE Center has developed a prototype instrument that monitors the stress in a
hanger plate top infer conditions that may lead to future damage.
For more information, please contact either by e-mail or telephone.
Frank Jalinoos (202) 493-3082
frank.jalinoos@fhwa.dot.gov
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