FHWA NDE CENTER RESEARCH & DEVELOPMENT
Bridge Load Testing
The FHWA NDE Center recently assisted the Maryland State Highway Administration (SHA)
in the load rating of one of their bridges. A steel superstructure, multi-girder highway bridge located on a major interstate outside
Baltimore was tested in cooperation with the SHA. This bridge had experienced impact damaged due to an overheight vehicle.
Given the location of the bridge and the possible repair costs, the SHA felt that a load test was necessary to carefully examine the
extent of the damage before any repair procedures were implemented.
Given the high traffic at the bridge site, using conventional instrumentation to load rate the structure would have been
disruptive to the public. In an effort to address this type of situation, the FHWA NDE Center has been developing instrumentation to more
efficiently load rate bridges with minimal access to a bridge and minimal effect on traffic. To achieve this goal a laser-based
measurement instrument is used to remotely measure girder deflections under known static loads. No targets or surface
preparations of the girder are necessary and the system can be used on both steel and concrete structures.
During the SHA bridge test, the traffic pattern under the structure was not altered. From the shoulder of the roadway under
the bridge the laser system measured deflections at 45 different locations along the length of three 25-m long girders. Traffic on
the structure was only briefly disrupted for placement of a load vehicle. The load test was completed in about 2 hours, which
included instrument setup and the collection of 7 data sets under various load configurations. Data from the test were provided to
the SHA for their use in load rating the bridge.
Please contact Dr. Paul Fuchs
by email or by telephone at (202) 493-3095 for More Information.
Figure 1. The FHWA NDE Center Laser System in use at the bridge load test site
Figure 2. The FHWA NDE Center Laser System as positioned under the bridge structure for testing
Figure 3. Sample Data from the Load Testing
Other applications of the FHWA NDE Center Laser System:
Steel Bridge Fabrication
FHWA Curved Girder Bridge Study
GRS Abutments
