FHWA NDE CENTER RESEARCH & DEVELOPMENT
Feasibility of Strengthening Concrete Beams
Using Bonded Composite Laminate
Federal Highway Administration (FHWA) Nondestructive Evaluation (NDE) Center in collaboration with New York State DOT (NYSDOT) is conducting a test program to evaluate the effectiveness of carbon fiber laminate repairs on deteriorated prestressed box girders. The objectives of the project are as follows:
- Determine the actual load carrying capacity of the deteriorated box beams, and test the accuracy of models developed by NYSDOT and FHWA.
- Evaluate the effectiveness of bonded carbon fiber laminates for increasing the load carrying capacity of severely deteriorated box girder.
- Evaluate existing NDE technologies for the evaluation of deteriorated box girders and bonded carbon fiber laminate installations.
- Develop design and construction guidelines for using bonded composite laminates for strengthening prestressed concrete box girders in the State of New York.
This research will ultimately help in reducing the number of prestressed concrete bridges rated as structurally deficient,
consistent with the strategic goals of the FHWA.
Background
Five prestressed box beams were salvaged from a bridge replacement project in 1997 in up-state New York. The purpose of
salvaging these girders was twofold. The first was to provide the FHWA NDE Center with unique specimens containing corroded and broken
prestressed stands, spalling etc.. The unique specimens will provide a test-bed for the development and evaluation of nondestructive
techniques for prestressed concrete structures. The second purpose was to perform load test on several salvaged box girders to
assist NYSDOT in research concerning the use of bonded carbon laminates.
Figure 1. Box Beams in place in NY State prior
to bridge replacement
Test Plan Summary
To evaluate the strength of the existing girders, two load tests were preformed on the salvaged prestressed box girders in
their natural state. Following these tests, composite laminates were installed on a third girder, and the girder was tested to
failure. Finally three girders will be placed in fall 2000 on on-site test bridge (Geosynthetic Reinforced Soil (GRS) abutments)
that will allow for the evaluation of load rating techniques for detection of corroded and broken strands. A test summary and
schedule is shown below:
Test 1. Load Test of deteriorated box girder
Goal: This load test will determine the elastic limit of the girders to be used in the final test bridge configuration, and
validate models to predict the strength of deteriorated girders. It will also provide the necessary data for the design of
carbon laminate installation.
Test Date: October 19, 1999.
Status: Test completed, data analysis ongoing
Figure 2. Test Setup
Test 2: Load test of intact girder
Goal: Test 2 will be used to determine the actual strength of a girder that which appears to be intact. The data will be used
to evaluate the effectiveness of the composite installation, and to validate models.
Test Date: December 9, 1999
Status: Test completed, data analysis ongoing.
Test 3: Load test of composite laminate reinforced girder
Goal: This test will be used to evaluate the effectiveness of carbon bonded overlay for use as a strengthening tool in
prestressed girders. The test will also be used to validate design procedures and models, and to develop guidelines for use in the
State of New York.
Test Date: August 1, 2000
Status: Test completed, data analysis ongoing.
Figure 3. Test 3 at Failure Load
Test 4: Load test of on-site test bridge
Goal: Test 4 will evaluate the load carrying capacity of an on-site test bridge, to provide loading for a test of the GRS abutments, and the loading rating tools developed through the NDE program.
Test Date: Fall 2000.
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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