PROBLEM STATEMENT
The use of the recently approved TL-3 F-shaped precast concrete barrier detail is often used in reinforced concrete bridge decks where both transverse and longitudinal reinforcing steel exists. The current Louisiana barrier detail has a slotted hole design that allows for shifting of the pin to avoid transverse reinforcement. To avoid rebar in the longitudinal direction, the Contractor would be required to physically shift the barrier transversely. Contractors often complain that the barrier and pin connection is often difficult to avoid conflicts with the reinforcing steel and many are ignorant or do not wish to use Non-Destructive Testing (NDT) methods to locate reinforcing steel in bridge decks.
BACKGROUND
Non-Destructive Testing (NDT) methods are popular for routine inspection of bridge members. Also, thanks to new technology developments, they are becoming more economically feasible for bridge inspection. With the ability of new highly technical systems, some of these NDT techniques can be used for reinforcing steel rebar location in concrete bridge decks without destruction of the members being tested. Use of these techniques has the ability to minimize traffic restrictions related to field data collection and to improve design and asset management. They can be applied to pre and post-construction performance monitoring and data collection while considerably minimizing unwelcome breaks related to highway renewal. These advanced inspection techniques can be expensive due to the need of having professionally trained technicians to perform the testing and to acquire and analyze the inspection results. Also, some of these methods require calibrated testing equipment (Wimsatt et al., 2009). Examples of NDT techniques that can be used for rebar location are Ground-Penetrating Radar (GPR) , laser ultrasonic testing, magnetic devices such as pachometers and magnetic imaging tools.
OBJECTIVE
The objective of this study is to perform a literature search to determine the current NDT methods available for detecting locations of the reinforcing steel in bridge decks in order to allow contractors for more accurately locating the placement of the concrete barrier rails during construction. Each method should be researched to determine equipment cost, user cost, and advantages/disadvantages for each method. A recommendation should be given on the most efficient method to be used for State Department of Transportation (DOT).
BENEFITS
The research would identify methods that could be used by the General Contractors to accurately locate reinforcing steel. These methods could be added to the State DOT specifications that would require their use on applicable projects.
PRODUCTS
TTI will generate a report providing with detailed description of currently used NDT methods to locate reinforcing steel in bridge decks. Comparison of different methods will be completed with regard to equipment costs, user cost, advantages and disadvantages. Tolerances with each method will be documented. In addition, the report will include recommendation on the most efficient NDT method(s) to be used for State DOT.
IMPLEMENTATION
Recommendation regarding use of most efficient NDT method(s) to locate reinforcing steel in bridge decks will be suggested to be used for Louisiana Department of Transportation.
WORK PLAN
Task 1 –Conduct literature review on NDT methods to locate reinforcing steel in bridge decks
The researchers will perform a review of the current NDT methods used to locate reinforcing steel in bridge decks. Evaluation of the available methods will be performed in term of equipment and user costs, advantages and disadvantages for each technique.
Task 2 –Test NDT rebar locating devices obtained from the literature search
The researchers will test two, maybe three NDT devices which were obtained from the literature search. Available steel-reinforced bridge decks at TTI will be used to verify the use easiness and accuracy of such NDT methods in locating the reinforcing steel. Drawings of test decks are available and, if necessary, researchers will be able to expose them to have accurate information on spacing of the reinforcing steel. Also, researchers will choose NDT devices with a tight tolerance, so that their use will be appropriate if rebar spacing is relatively small. This information will be used to validate the NDT methods used for testing.
Task 3 –Generate final report
The researchers will generate a final report of the findings from the literature search and the tests conducted. In addition, the report will include recommendation on the most efficient NDT method(s) to be used for State DOT.
| TTI Research Supervisor: Chiara Silvestri, Ph.D. Texas Transportation Institute Texas A&M University System 3135 TAMU College Station, Texas 77843-3135 (979) 845-8971 c-silvestri@ttimail.tamu.edu |
Pooled Fund Technical Representative: Paul Fossier Assistant Bridge Design Administrator Bridge and Structural Design Section Louisiana Transportation Center 1201 Capitol Road P.O. Box 94245 Baton Rouge, LA 79084-9245 (225) 379-1323 Paul.Fossier@la.gov |
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Wimsatt A.J., Scullion T., Fernando E., Hurlebaus S., Lyiton R., and Zollinger D. (2009) “A Plan for Developing High-Speed, Nondestructive Testing Procedures for Both Design Evaluation and Construction Inspection.” The Second Strategic Highway Research Program, Trasportation Research Board. Washington, D.C.
